Ci a ion: Mancisido , A.M.;
Ga cía-Blanco, M.B.; Quin ana, I.;
A azola, P.J.; Espinosa, E.; Cues a,
M.; Albizu i, J.; Ga ciandia, F. E ec
o Pos -P ocessing T ea men on
Fa igue Pe o mance o Ti6Al4V
Alloy Manu ac u ed by Lase Powde
Bed Fusion. J. Manu . Ma e . P ocess.
2023,7, 119. h ps://doi.o g/
10.3390/jmmp7040119
Academic Edi o s: A e Yadollahi
and Mohammad Mah abi
Recei ed: 14 May 2023
Re ised: 9 June 2023
Accep ed: 16 June 2023
Published: 22 June 2023
Copy igh : © 2023 by he au ho s.
Licensee MDPI, Basel, Swi ze land.
This a icle is an open access a icle
dis ibu ed unde he e ms and
condi ions o he C ea i e Commons
A ibu ion (CC BY) license (h ps://
c ea i ecommons.o g/licenses/by/
4.0/).
Manu ac u ing and
Ma e ials P ocessing
Jou nal o
A icle
E ec o Pos -P ocessing T ea men on Fa igue Pe o mance o
Ti6Al4V Alloy Manu ac u ed by Lase Powde Bed Fusion
Ane Mi en Mancisido 1,* , Ma ía Belén Ga cía-Blanco 2, Iban Quin ana 3, Ped o JoséA azola 4,
Elixabe e Espinosa 2, Mikel Cues a 4, Joseba Albizu i 5and Fe min Ga ciandia 1
1Lo ek, Basque Resea ch and Technology Alliance (BRTA), A anomendia Kalea 4A,
20240 O dizia, Gipuzkoa, Spain; ga [email p o ec ed]
2Cide ec, Basque Resea ch and Technology Alliance (BRTA), Po. Mi amón 196,
20014 Donos ia-San Sebas ián, Gipuzkoa, Spain; [email p o ec ed] (M.B.G.-B.); [email p o ec ed] (E.E.)
3Teknike , Basque Resea ch and Technology Alliance (BRTA), C/Iñaki Goenaga, 5,
20600 Eiba , Gipuzkoa, Spain; iban.quin ana@ eknike .es
4Facul y o Enginee ing, Mond agon Unibe si a ea, Lo amendi 4, 20500 A asa e-Mond agon, Gipuzkoa,
Spain; [email p o ec ed] (P.J.A.); [email p o ec ed] (M.C.)
5
Facul y o Enginee ing, Depa men o Mechanical Enginee ing, Uni e si y o he Basque Coun y UPV/EHU,
Plaza Ingenie o To es Que edo 1, 48013 Bilbao, Bizkaia, Spain; [email p o ec ed]
*Co espondence: [email p o ec ed]; Tel.: +34-688-729-606
Abs ac :
Fa igue p ope ies o pa s a e o pa icula conce n o sa e y-c i ical s uc u es. I is well-
known ha discon inui ies in shape o non-uni o mi ies in ma e ials a e equen ly a po en ial nucleus
o a igue ailu e. This is especially c ucial o he Ti6Al4V alloy, which p esen s high suscep ibili y
o he no ch e ec . This s udy in es iga es how pos -p ocessing ea men s a ec he mechanical
pe o mance o Ti6Al4V samples manu ac u ed by lase powde bed usion echnology. All he a igue
samples we e subjec ed o a HIP cycle and pos -p ocessed by machining and using combina ions
o al e na i e mechanical and elec ochemical su ace ea men s. The ela ionship be ween su ace
p ope ies such as oughness, opog aphy and esidual s esses wi h a igue pe o mance was
assessed. Comp essi e esidual s esses we e in oduced in all su ace- ea ed samples, and a e
ibo inishing, oughness was educed o 0.31
±
0.10
µ
m, which was ound o be he mos c i ical
ac o . F ac u es occu ed on he su ace as HIP emo ed c i ical in e nal de ec s. The i egula i ies
ound in he o m o ca i ies o pi s we e s ess concen a o s ha ini ia ed c acks. I was concluded
ha machined su aces p esen ed a a igue beha io compa able o w ough ma e ial, o e ing a
a igue limi supe io o 450 MPa. Addi ionally, al e na i e su ace ea men s showed a a igue
beha io equi alen o he cas ing ma e ial.
Keywo ds:
lase powde bed usion; Ti6Al4V; su ace modi ica ion; a igue s eng h; esidual s esses;
su ace oughness
1. In oduc ion
Addi i e manu ac u ing (AM) has s ongly eme ged in ecen yea s as a dis up i e
echnology. I comp ises a se o di e en p ocesses which sha e a common idiosync asy,
he shaping o physical componen s di ec ly om digi al da a by he con olled deposi-
ion o ma e ial in a laye -by-laye ashion. Due o i s addi i e na u e, AM echnologies
en ail he ollowing main bene i s: maximum ma e ial esou ce e iciency, almos unlimi ed
design complexi y, maximum lexibili y and cus omiza ion possibili ies in sho de elop-
men imes.
Ti6Al4V is by a he me al alloy ha has been mo e la gely s udied in AM applica ions.
The e a e hund eds o ema kable scien i ic e e ences abou he manu ac u ing o Ti6Al4V
by bo h di ec ed ene gy deposi ion and powde bed usion echnologies [
1
]. This ex ended
p edilec ion o he de elopmen o AM o he Ti6Al4V alloy is due o i s ou s anding combi-
na ion o physical p ope ies including high s eng h, low densi y, high co osion esis ance
J. Manu . Ma e . P ocess. 2023,7, 119. h ps://doi.o g/10.3390/jmmp7040119 h ps://www.mdpi.com/jou nal/jmmp
J. Manu . Ma e . P ocess. 2023,7, 119 2 o 21
and good biocompa ibili y, being he p e e ed ma e ial o ae ospace and biomedical
applica ions [
2
]. In addi ion, i supposes a high added alue in he ae ospace and biomedi-
cal sec o s.
Despi e he signi ican po en ial ad an ages o AM, a p ima y conce n o any s uc-
u al applica ion is o ensu e he epea abili y and eliabili y o mechanical pe o mance.
Acco ding o epo ed da a, s a ic mechanical p ope ies (yield s ess, ul ima e s eng h
and elonga ion) o AM Ti6Al4V pa s a e compa able o w ough coun e pa s.
Wi h espec o a igue pe o mance, which is a p ima y conce n o comme cial
ae ospace s uc u es, i has been ound ha AM i anium ma e ials can be compa able
o w ough ma e ials [
3
], bu a e highly suscep ible o issues associa ed wi h AM, such
as de ec s, esidual s ess, build o ien a ion and su ace condi ion. Po es, lack o usion
o c acks can ac as po en ial s ess aise s, leading o p ema u e ailu e unde a igue
loading [
4
]. De ec s which a e loca ed close o he su ace a e especially c i ical [
5
]. In
his espec , Leude s e al. [
6
] concluded ha esidual po osi y has a di ec e ec on
a igue beha io . Addi ionally, su ace oughness p o ides s ess concen a ions in hei
su oundings and can cause c ack ini ia ion, al hough keeping he in e nal de ec s o a
minimum [7].
Cen e ed in he lase powde bed usion (L-PBF) p ocess, he high cooling a es
inhe en in he p ocess may cause esidual s esses in he manu ac u ed pa s. I is widely
known ha ensile esidual s esses should be a oided in a igue loading because hey
p omo e he ini ia ion and p opaga ion o c acks [8].
I is essen ial o ackle in conjunc ion all he issues men ioned ha ha e a nega i e
impac on a igue beha io , so ha s a egies ha minimize de ec s, imp o e su ace quali y
and educe esidual s esses a e applied. S a egies ha only imp o e pa ially he a igue-
in luencing issues will no induce a su icien bene i in a igue esponse [
9
]. Fo ins ance,
pa s manu ac u ed by L-PBF a e subjec ed o s ess elie hea ea men s in o de o
emo e esidual s esses. Ne e heless, as demons a ed by [
10
], sca e ing o esul s can be
achie ed in a igue es ing due o he p esence o po es which accele a e he c ack g ow h.
An e ec i e s a egy o educe o e en close esidual de ec s emaining om he AM
p ocess is ho isos a ic p essing (HIP). HIP has a di ec in luence on he emo al o in e nal
de ec s and esidual s esses and on he modi ica ion o he mic os uc u e owa ds a mo e
duc ile ma e ial leading o imp o ed a igue beha io , while he su ace condi ion emains
unchanged [
11
–
14
]. None heless, a he same ime, i is impe a i e o imp o e su ace
quali y by educing he oughness o AM pa s [
15
]. Roughness has been e i ied o be he
mos c ucial pa ame e in a igue, mo e han he p esence o de ec s, esidual s esses o
mic os uc u e. Acco ding o [
16
], HIPed samples did no show signi ican imp o emen s
in a igue li e wi h ough as-buil su aces. Fa igue beha io was domina ed by he ough
su ace a he han by in e nal de ec s o he ma e ial.
Machining is one o he mos common ea men s o su ace modi ica ion o AM pa s
and leads o he highes a igue s eng h i combined wi h HIP ea men [
17
]. As explained
by Kahlin [
16
], he ac u e mechanism is changed in machined samples wi h espec o
as-buil ough ones. C acks ini ia e in he in e io o subsu ace o machined samples,
whe eas c acks occu on he su ace o as-buil pa s. I is wo h no ing ha as-buil and
machined samples can show a simila esponse o a igue [
18
], despi e ha ing educed
oughness, in he p esence o a high amoun o in e nal de ec s. In ac , hese in e nal
de ec s become subsu ace de ec s because hey appea on he su ace du ing machining.
Keeping low le els o in e nal de ec s, Xu e al. [
19
] e idenced ha machining imp o es
a igue s eng h because i elimina es su ace po osi y.
Ne e heless, su ace quali y imp o emen by he educ ion in oughness should be
add essed by o he me hods a he han by machining. The complexi y o AM pa s is e y
high, so in mos cases, no all su aces a e accessible o machining [
20
]. Un o una ely,
mos o he in es iga ed al e na i e su ace ea men s a e no sui able o complex pa s.
Among he di e en su ace ea men s, sho peening has been he mos ex ended me hod
applied o AM Ti6Al4V pa s. Al hough i is no e y sui able o inaccessible su aces,
J. Manu . Ma e . P ocess. 2023,7, 119 3 o 21
i imp o es a igue s eng h and a igue li e by educing oughness and by in oducing
comp essi e esidual s esses which p e en he ini ia ion o a igue ailu e [
21
]. O he
a ian s o sho peening such as lase peening and ca i a ion peening ac in a simila way
bu wi h enhanced a igue p ope ies [22].
Yan e al. [
23
] suppo ed ha addi ional me hods based on ul asounds, such as ul a-
sonic impac ea men , ul asonic su ace mechanical a i ion and ul asonic nanoc ys al
su ace modi ica ion, induce a plas ic de o ma ion which esul s in esidual comp essi e
s esses, a o ing a igue li e. They indica ed ha he disad an age o ul asonic nanoc ys-
al su ace modi ica ion is ha i is no applicable o complex geome ies. The expe imen s
conduc ed by [
24
] showed ha he ul asonic impac ea men dis ibu es esidual s esses
and gene a es a ha dened su ace. Addi ionally, i is able o close su ace po osi y and
educe oughness. All hese ac s imp o e a igue p ope ies.
A non-con ac su ace inishing is called ex eme iso opic supe inishing (ISF). I is a
chemically accele a ed ib a o y inishing ha is based on he chemical con e sion o a
hin su ace laye ha is subsequen ly emo ed by con ac wi h ib a ing, non-ab asi e
media. Wi kin e al. [
25
] applied his su ace ea men o Ti6Al4V pa s manu ac u ed by
L-PBF echnology. High cycle a igue p ope ies we e imp o ed wi h espec o non- ea ed
samples. Acco ding o hese au ho s, he imp o emen is based on he educ ion in su ace
oughness a he han esidual s ess modi ica ions. The o e all su ace oughness is
imp o ed and sha p c ack-like ea u es a e expanded and ounded, a oiding he o ma ion
o a igue c acks.
As-buil su ace quali y can be also imp o ed by mo e con en ional s a egies such as
sandblas ing, ibo inishing and chemical and elec ochemical polishing, which a e mo e
economical and easily indus ialized compa ed o he p e iously men ioned ones. Fo
ins ance, sandblas ing is he mos used p ocess o educe he su ace as oughness o
L-PBF pa s and i is app op ia e o emo e adhe ed powde pa icles. Al hough a wa ed
su ace is achie ed, sandblas ing can imp o e a igue p ope ies compa ed o as-buil
condi ions [
26
]. Wi hin chemical ea men s, chemical e ching is able o elimina e de ec i e
laye s and adhe ed pa icles, imp o ing a igue s eng h [
14
]. Elec opolishing can p oduce
b igh su aces wi h smoo hed high poin s and low egions wi h a pooled look. I has been
demons a ed ha he applica ion o elec opolishing a e a mechanical ea men such as
sho peening could educe he su ace oughness by mo e han hal and p o ide signi ican
imp o emen s in a igue esis ance, especially o high cycle a igue egimes [27].
Finally, we can men ion he ibo inishing me hod o smoo h su aces, du ing which
he pa s a e ib a ed in a ank wi h ab asi es. In [
9
], L-PBF Ti6Al4V pa s we e ibo in-
ished a e pe o ming a s ess elie hea ea men and HIPing. They achie ed a igue
limi s o 325 MPa o s ess- elie ed pa s and 350 MPa o HIPed samples.
In conclusion, ocusing on su ace inishing me hods o Ti6Al4V p ocessed by AM,
machining is he op ion ha esul s in he highes a igue s eng h and a igue li e, ob ain-
ing alues compa able o con en ional w ough ma e ial. The as majo i y o su ace
ea men s do no ha e such a la ge impac on a igue p ope ies, and he mos s udied ones
do no imply con en ional su ace echnologies which, in he end, a e mo e economical and
could be mo e easily managed by AM pa manu ac u e s. Mo eo e , he a igue p ope ies
o Ti6Al4V alloys p ocessed by L-PBF echnology and pos -p ocessed wi h con en ional
mechanical and elec ochemical echnologies ha e no been p e iously compa ed among
hem and wi h he machining p ocess. The e o e, his s udy ocused on he analysis o
he e ec o con en ional su ace modi ica ion app oaches such as ibo inishing, sand-
blas ing and elec opolishing applied a e sandblas ing (E-Blas ing p ocess) on he su ace
oughness educ ion, esidual s ess and a igue beha io o a Ti6Al4V alloy p oduced by
L-PBF. The ob ained esul s we e compa ed wi h samples wi h machined su aces and
con en ionally cas and w ough Ti6Al4V ma e ials.
J. Manu . Ma e . P ocess. 2023,7, 119 4 o 21
2. Ma e ials and Me hods
2.1. Powde Bed Sample Fab ica ion
All he es samples we e p oduced using G ade 23 Ti6Al4V powde p o ided by
Ca pen e Technology. This powde , a omized in an a gon a mosphe e, had a pa icle size
ange om 20 o 63
µ
m wi h an a e age pa icle size o 37
µ
m. LECO analysis e ealed
an oxygen le el o 0.086% in he as- ecei ed condi ion. Figu e 1shows he sphe ical
mo phology o he powde employed in his s udy which assu ed good lowabili y.
J. Manu . Ma e . P ocess. 2023, 7, x FOR PEER REVIEW 4 o 21
2. Ma e ials and Me hods
2.1. Powde Bed Sample Fab ica ion
All he es samples we e p oduced using G ade 23 Ti6Al4V powde p o ided by
Ca pen e Technology. This powde , a omized in an a gon a mosphe e, had a pa icle size
ange om 20 o 63 µm wi h an a e age pa icle size o 37 µm. LECO analysis e ealed
an oxygen le el o 0.086% in he as- ecei ed condi ion. Figu e 1 shows he sphe ical mo -
phology o he powde employed in his s udy which assu ed good lowabili y.
(a) (b)
Figu e 1. SEM images o gas-a omized Ti6Al4V powde . (a) Low magni ica ion showing sphe ical
pa icles (b) De ails o powde pa icles
The MCP Realize 250 L-PBF sys em, supplied by MTT G oup (S one, Ken , UK), was
employed o build he es samples. This machine was i ed wi h an IPG ibe lase (Y -
e bium lase in solid s a e) om IPG Pho onics manu ac u e (Ox o d, UK) wi h a wa e-
leng h be ween 1085 and 1090 nm and a maximum powe o 200 W. The manu ac u ing
was ca ied ou in an a gon p o ec i e a mosphe e. The pla o m was hea ed o 200 °C.
Op imized p ocess pa ame e s we e used o gua an ee a densi y supe io o 99.9%.
2.2. Pos -P ocessing o Tes ing Samples
The manu ac u ed samples we e subjec ed o a ho isos a ic p essing (HIP) cycle o
emo e possible emaining esidual de ec s. Samples we e HIPed a 920 °C and 100 MPa
o 2 h unde an a gon gas a mosphe e. HIP ea men s we e pe o med by Bodyco e SAS
Eu opean G oup. Addi ionally, a con en ional hea ea men was conduc ed on some o
he a igue samples. This cycle consis ed o hea ing he samples o 850 °C in acuum o 5
h.
Va ious su ace modi ica ion me hods (sandblas ing, elec opolishing and ibo in-
ishing) we e hen applied o hipped a igue samples in o de o e alua e hei in luence
on a igue pe o mance. In addi ion, he combined e ec o sandblas ing and elec-
opolishing was also assessed. This su ace ea men was labeled as E-Blas ing. Fo he
sake o compa ison, he su aces o a numbe o a igue samples we e machined. Only he
leng h o he gauge a ea o a igue samples was pos -p ocessed wi h he abo e-men ioned
me hods. All he heads we e machined o assu e co ec clamping du ing a igue es s.
2.2.1. Sand Blas ing
Samples we e blas ed using co undum o 90–105 µm (angula shape) wi h a p essu e
d op ac oss he nozzle o 5.5 MPa, a a 4 cm dis ance om he nozzle o he pa , o 4 min.
2.2.2. E-Blas ing
E-Blas ing was ca ied ou by combining he desc ibed sandblas ing p ocess and an
elec opolishing ea men ha was ca ied ou a 30 °C, a a cons an ol age (38 V) o 20
min. The elec opolishing elec oly e was a non-aqueous one, comp ising e hyl alcohol
Figu e 1.
SEM images o gas-a omized Ti6Al4V powde . (
a
) Low magni ica ion showing sphe ical
pa icles (b) De ails o powde pa icles.
The MCP Realize 250 L-PBF sys em, supplied by MTT G oup (S one, Ken , UK),
was employed o build he es samples. This machine was i ed wi h an IPG ibe lase
(Y e bium lase in solid s a e) om IPG Pho onics manu ac u e (Ox o d, UK) wi h a
wa eleng h be ween 1085 and 1090 nm and a maximum powe o 200 W. The manu ac u ing
was ca ied ou in an a gon p o ec i e a mosphe e. The pla o m was hea ed o 200
◦
C.
Op imized p ocess pa ame e s we e used o gua an ee a densi y supe io o 99.9%.
2.2. Pos -P ocessing o Tes ing Samples
The manu ac u ed samples we e subjec ed o a ho isos a ic p essing (HIP) cycle o
emo e possible emaining esidual de ec s. Samples we e HIPed a 920
◦
C and 100 MPa
o 2 h unde an a gon gas a mosphe e. HIP ea men s we e pe o med by Bodyco e SAS
Eu opean G oup. Addi ionally, a con en ional hea ea men was conduc ed on some o
he a igue samples. This cycle consis ed o hea ing he samples o 850
◦
C in acuum o
5 h.
Va ious su ace modi ica ion me hods (sandblas ing, elec opolishing and ibo inish-
ing) we e hen applied o hipped a igue samples in o de o e alua e hei in luence on
a igue pe o mance. In addi ion, he combined e ec o sandblas ing and elec opolishing
was also assessed. This su ace ea men was labeled as E-Blas ing. Fo he sake o com-
pa ison, he su aces o a numbe o a igue samples we e machined. Only he leng h o he
gauge a ea o a igue samples was pos -p ocessed wi h he abo e-men ioned me hods. All
he heads we e machined o assu e co ec clamping du ing a igue es s.
2.2.1. Sand Blas ing
Samples we e blas ed using co undum o 90–105
µ
m (angula shape) wi h a p essu e
d op ac oss he nozzle o 5.5 MPa, a a 4 cm dis ance om he nozzle o he pa , o 4 min.
2.2.2. E-Blas ing
E-Blas ing was ca ied ou by combining he desc ibed sandblas ing p ocess and an
elec opolishing ea men ha was ca ied ou a 30
◦
C, a a cons an ol age (38 V) o
20 min. The elec opolishing elec oly e was a non-aqueous one, comp ising e hyl alcohol
(700 mL L
−1
), isop opyl alcohol (300 mL L
−1
), AlCl3 (60 g L
−1
) and ZnCl2 (250 g L
−1
). A
J. Manu . Ma e . P ocess. 2023,7, 119 5 o 21
wo-elec ode sys em was used, wi h he anode being he Ti6Al4V a igue sample and he
ca hode being a ci cula Cp Ti mesh.
2.2.3. T ibo inishing
The pa s we e ib a ed using wo di e en ypes o ou es (Table 1). The p ocess
pa ame e s ha we e modi ied o s udy hei in luence on he inal oughness (and he e o e
on he a igue li e o he pa s) a e desc ibed below. Th ee aspec s we e modi ied as inpu
pa ame e s: ab asi e chip (M), chemical p oduc (Q) and ime (T).
1. Ab asi e chip (M) (Figu e 2).
•Ab asi e 1: SAAP Cylind ical Cham e ed 4 ×10;
•Ab asi e 2: Ce amic CAT 5 ×5 AB20.
2. Chemical p oduc (Q).
•Chemical p oduc 1: METALENE TPR 3%;
•Chemical p oduc 2: METALENE Be a 2%.
3. Time (T).
Table 1. Rou es employed in ibo inishing.
Rou e
Phase 1 Phase 2 Phase 3 D ying
M Q T (h) M Q T (h) M Q T (h) T (h)
1 2 1 5 1 1 15.25 1 2 0.25 6.5
2 2 1 15 1 1 21 1 2 4 32
J. Manu . Ma e . P ocess. 2023, 7, x FOR PEER REVIEW 5 o 21
(700 mL L−1), isop opyl alcohol (300 mL L−1), AlCl3 (60 g L−1) and ZnCl2 (250 g L−1). A wo-
elec ode sys em was used, wi h he anode being he Ti6Al4V a igue sample and he ca h-
ode being a ci cula Cp Ti mesh.
2.2.3. T ibo inishing
The pa s we e ib a ed using wo di e en ypes o ou es (Table 1). The p ocess
pa ame e s ha we e modi ied o s udy hei in luence on he inal oughness (and he e-
o e on he a igue li e o he pa s) a e desc ibed below. Th ee aspec s we e modi ied as
inpu pa ame e s: ab asi e chip (M), chemical p oduc (Q) and ime (T).
1. Ab asi e chip (M) (Figu e 2).
Ab asi e 1: SAAP Cylind ical Cham e ed 4 × 10;
Ab asi e 2: Ce amic CAT 5 × 5 AB20.
2. Chemical p oduc (Q).
Chemical p oduc 1: METALENE TPR 3%;
Chemical p oduc 2: METALENE Be a 2%.
3. Time (T).
Table 1. Rou es employed in ibo inishing.
Rou e Phase 1 Phase 2 Phase 3 D ying
M Q T (h) M Q T (h) M Q T (h) T (h)
1 2 1 5 1 1 15.25 1 2 0.25 6.5
2 2 1 15 1 1 21 1 2 4 32
Figu e 2. Ab asi e chips conside ed in ibo inishing.
The chemical p oduc used was composed o a mix u e o soaps, an ioxidan s, b igh -
ene s and speci ic addi i es p o ided by he company esponsible o supplying he di -
e en p oduc s necessa y o he ibo inishing p ocess (sel - o mula ion).
2.2.4. Machining
Samples we e machined by u ning and polishing o a inal su ace oughness o 0.4
µm Ra.
2.3. Tes ing o Samples
2.3.1. Tensile Tes ing
Cylind ical dog-bone-shaped samples (Figu e 3a) we e manu ac u ed in he e ical
di ec ion (pa allel o he building di ec ion (z)). Tensile es ing was pe o med acco ding
o ASTM E8 s anda d a oom empe a u e using he Zwick Roell Z100 (Ba celona, Spain)
ensile es ing machine wi h an ex e nal ex ensome e . Tensile samples we e es ed in he
Figu e 2. Ab asi e chips conside ed in ibo inishing.
The chemical p oduc used was composed o a mix u e o soaps, an ioxidan s, b igh en-
e s and speci ic addi i es p o ided by he company esponsible o supplying he di e en
p oduc s necessa y o he ibo inishing p ocess (sel - o mula ion).
2.2.4. Machining
Samples we e machined by u ning and polishing o a inal su ace oughness o
0.4 µm Ra.
2.3. Tes ing o Samples
2.3.1. Tensile Tes ing
Cylind ical dog-bone-shaped samples (Figu e 3a) we e manu ac u ed in he e ical
di ec ion (pa allel o he building di ec ion (z)). Tensile es ing was pe o med acco ding
o ASTM E8 s anda d a oom empe a u e using he Zwick Roell Z100 (Ba celona, Spain)
ensile es ing machine wi h an ex e nal ex ensome e . Tensile samples we e es ed in he
machined su ace condi ion, in he as- ab ica ed s a e (wi hou any hea ea men ) and
a e pe o ming he HIP ea men . Th ee samples pe condi ion we e es ed.
J. Manu . Ma e . P ocess. 2023,7, 119 6 o 21
2.3.2. Fa igue Tes ing
Fa igue samples we e manu ac u ed in he e ical di ec ion (z). Hou glass a igue
samples we e es ed as speci ied in Figu e 3b.
J. Manu . Ma e . P ocess. 2023, 7, x FOR PEER REVIEW 6 o 21
machined su ace condi ion, in he as- ab ica ed s a e (wi hou any hea ea men ) and
a e pe o ming he HIP ea men . Th ee samples pe condi ion we e es ed.
2.3.2. Fa igue Tes ing
Fa igue samples we e manu ac u ed in he e ical di ec ion (z). Hou glass a igue
samples we e es ed as speci ied in Figu e 3b.
(a) (b)
Figu e 3. (a) Tensile samples’ geome y and (b) a igue samples’ geome y. Uni : mm.
Ro a ing bending a igue es s we e ca ied ou using a Zwick/Roell model 200TC
UBM machine (Ba celona, Spain) and acco ding o ISO 1143 ( o a ing bending es s).
These o a ing bending es s we e pe o med in he high cycle a igue (HCF) egime wi h
a equency o 100 Hz and a oom empe a u e. A un-ou o 5 106 cycles was es ab-
lished.
All he samples we e HIPed and subsequen ly subjec ed o he su ace ea men s
de ailed p e iously be o e pe o ming he a igue es s. A minimum o six samples pe
condi ion we e es ed. As a s a ing poin , as-buil oughness was also e alua ed.
2.4. Samples Cha ac e iza ion
The su ace oughness o he a igue samples was measu ed using an In a 50 mm
(Taylo Hobson b and, Leices e , UK) p o ilome e . Fil e pa ame e s o calcula e he
oughness pa ame e s Ra we e selec ed acco ding o he UNE-EN ISO 4288 s anda d. Su -
ace opog aphy was cha ac e ized using a Leica DCM 3D (We zla , Ge many) con ocal
mic oscope and he mo phology was analyzed in each su ace condi ion by he FE-SEM
Ul a Plus scanning elec on mic oscope om Zeiss, equipped wi h a composi ional anal-
ysis module (EDS).
The mic os uc u e in he as-buil s a e and in he HIP condi ion was cha ac e ized
in o de o es ablish a connec ion wi h s a ic mechanical p ope ies. Fo ha , samples we e
me allog aphically p epa ed by g inding wi h SiC pape and polishing o a mi o inish.
Mic og aphs o he p epa ed su aces we e ob ained wi h he same FE-SEM equipmen .
Mo eo e , densi y wi h and wi hou HIP ea men was measu ed o p o e he e ec i e-
ness o HIP ea men in educing esidual po osi y. Rela i e densi y was de e mined by
an op ical mic oscope (GX51 Olympus, Hambu g, Ge many) and using Image-J image
analysis so wa e.
Axial esidual s esses (ARS) we e analyzed by he X- ay di ac ion echnique
(B uke X-Ray di ac ome e D8 wi h Cu adia ion) using he sin2Ψ [28] me hod on he
su aces o he a igue samples. The a eas whe e he di e en pos -p ocessing me hods
we e applied we e analyzed. Fo he de e mina ion o he in-plane s ess enso , di ac-
ion cu es o he di e en α (213) phase di ac ion peak be ween 138° < 2θ < 145° (θ is
he B agg angle) mus be ob ained wi h a leas h ee independen o a ion angles (Φ = 0°,
45° and 90°).
Finally, ac u e su aces o a igue samples we e s udied using he FE-SEM Ul a
Plus scanning elec on mic oscope o assess he o igin o he ac u e.
3. Resul s
Figu e 3. (a) Tensile samples’ geome y and (b) a igue samples’ geome y. Uni : mm.
Ro a ing bending a igue es s we e ca ied ou using a Zwick/Roell model 200TC
UBM machine (Ba celona, Spain) and acco ding o ISO 1143 ( o a ing bending es s). These
o a ing bending es s we e pe o med in he high cycle a igue (HCF) egime wi h a
equency o 100 Hz and a oom empe a u e. A un-ou o 5
×
10
6
cycles was es ablished.
All he samples we e HIPed and subsequen ly subjec ed o he su ace ea men s
de ailed p e iously be o e pe o ming he a igue es s. A minimum o six samples pe
condi ion we e es ed. As a s a ing poin , as-buil oughness was also e alua ed.
2.4. Samples Cha ac e iza ion
The su ace oughness o he a igue samples was measu ed using an In a 50 mm
(Taylo Hobson b and, Leices e , UK) p o ilome e . Fil e pa ame e s o calcula e he
oughness pa ame e s Ra we e selec ed acco ding o he UNE-EN ISO 4288 s anda d.
Su ace opog aphy was cha ac e ized using a Leica DCM 3D (We zla , Ge many) con ocal
mic oscope and he mo phology was analyzed in each su ace condi ion by he FE-SEM
Ul a Plus scanning elec on mic oscope om Zeiss, equipped wi h a composi ional analysis
module (EDS).
The mic os uc u e in he as-buil s a e and in he HIP condi ion was cha ac e ized in
o de o es ablish a connec ion wi h s a ic mechanical p ope ies. Fo ha , samples we e
me allog aphically p epa ed by g inding wi h SiC pape and polishing o a mi o inish.
Mic og aphs o he p epa ed su aces we e ob ained wi h he same FE-SEM equipmen .
Mo eo e , densi y wi h and wi hou HIP ea men was measu ed o p o e he e ec i eness
o HIP ea men in educing esidual po osi y. Rela i e densi y was de e mined by an
op ical mic oscope (GX51 Olympus, Hambu g, Ge many) and using Image-J image analysis
so wa e.
Axial esidual s esses (ARS) we e analyzed by he X- ay di ac ion echnique (B uke
X-Ray di ac ome e D8 wi h Cu adia ion) using he sin2
Ψ
[
28
] me hod on he su aces o
he a igue samples. The a eas whe e he di e en pos -p ocessing me hods we e applied
we e analyzed. Fo he de e mina ion o he in-plane s ess enso , di ac ion cu es o
he di e en
α
(213) phase di ac ion peak be ween 138
◦
< 2
θ
< 145
◦
(
θ
is he B agg angle)
mus be ob ained wi h a leas h ee independen o a ion angles (Φ= 0◦, 45◦and 90◦).
Finally, ac u e su aces o a igue samples we e s udied using he FE-SEM Ul a Plus
scanning elec on mic oscope o assess he o igin o he ac u e.
3. Resul s
3.1. E olu ion o he Mic os uc u e
The e ec i eness o he HIP ea men in emo ing de ec s o Ti6Al4V pa s manu ac-
u ed by he L-PBF p ocess was i s e alua ed. The maximum densi y achie ed wi h he
op imized p ocessing pa ame e s was 99.90%. The e o e, esidual de ec s we e obse ed
in as-buil samples. Only sphe ical po es we e de ec ed, and he e we e no lack o usion
J. Manu . Ma e . P ocess. 2023,7, 119 7 o 21
de ec s. The sou ce o po osi y could be in e nal po osi y p esen in he a omized powde
o gas en apmen du ing he manu ac u ing p ocess. This esidual po osi y dec eased sig-
ni ican ly a e pe o ming he HIP ea men , ob aining nea ly ully dense pa s (99.99%).
The in e nal quali y o he pa s is e idenced in he SEM images in Figu e 4.
J. Manu . Ma e . P ocess. 2023, 7, x FOR PEER REVIEW 7 o 21
3.1. E olu ion o he Mic os uc u e
The e ec i eness o he HIP ea men in emo ing de ec s o Ti6Al4V pa s manu-
ac u ed by he L-PBF p ocess was i s e alua ed. The maximum densi y achie ed wi h
he op imized p ocessing pa ame e s was 99.90%. The e o e, esidual de ec s we e ob-
se ed in as-buil samples. Only sphe ical po es we e de ec ed, and he e we e no lack o
usion de ec s. The sou ce o po osi y could be in e nal po osi y p esen in he a omized
powde o gas en apmen du ing he manu ac u ing p ocess. This esidual po osi y de-
c eased signi ican ly a e pe o ming he HIP ea men , ob aining nea ly ully dense
pa s (99.99%). The in e nal quali y o he pa s is e idenced in he SEM images in Figu e
4.
(a) (b)
Figu e 4. Residual po osi y o (a) as-buil samples and (b) HIPed samples.
As can be p esumed om Figu e 5, he mic os uc u e o Ti6Al4V can be conside a-
bly in luenced when applying he HIP ea men . As a esul o he L-PBF p ocess, a ine
mic os uc u e de eloped in a ma ensi ic (α’) needle shape due o he apid usion and
pos e io solidi ica ion (Figu e 5a,c). Howe e , a e he HIP he mal ea men a 920 °C,
below he β ansus (955 °C) empe a u e, he ine ma ensi ic mic os uc u e ans o med
in o a mix u e o α and β phases, whe e he α phase p esen s as ine pla es (Figu e 5b,d).
HIP ea men also induced a coa sening o he mic os uc u e compa ed o he o iginal
α’.
(a) (b)
Figu e 4. Residual po osi y o (a) as-buil samples and (b) HIPed samples.
As can be p esumed om Figu e 5, he mic os uc u e o Ti6Al4V can be conside ably
in luenced when applying he HIP ea men . As a esul o he L-PBF p ocess, a ine
mic os uc u e de eloped in a ma ensi ic (
α
’) needle shape due o he apid usion and
pos e io solidi ica ion (Figu e 5a,c). Howe e , a e he HIP he mal ea men a 920
◦
C,
below he
β
ansus (955
◦
C) empe a u e, he ine ma ensi ic mic os uc u e ans o med
in o a mix u e o
α
and
β
phases, whe e he
α
phase p esen s as ine pla es (Figu e 5b,d).
HIP ea men also induced a coa sening o he mic os uc u e compa ed o he o iginal
α
’.
J. Manu . Ma e . P ocess. 2023, 7, x FOR PEER REVIEW 7 o 21
3.1. E olu ion o he Mic os uc u e
The e ec i eness o he HIP ea men in emo ing de ec s o Ti6Al4V pa s manu-
ac u ed by he L-PBF p ocess was i s e alua ed. The maximum densi y achie ed wi h
he op imized p ocessing pa ame e s was 99.90%. The e o e, esidual de ec s we e ob-
se ed in as-buil samples. Only sphe ical po es we e de ec ed, and he e we e no lack o
usion de ec s. The sou ce o po osi y could be in e nal po osi y p esen in he a omized
powde o gas en apmen du ing he manu ac u ing p ocess. This esidual po osi y de-
c eased signi ican ly a e pe o ming he HIP ea men , ob aining nea ly ully dense
pa s (99.99%). The in e nal quali y o he pa s is e idenced in he SEM images in Figu e
4.
(a) (b)
Figu e 4. Residual po osi y o (a) as-buil samples and (b) HIPed samples.
As can be p esumed om Figu e 5, he mic os uc u e o Ti6Al4V can be conside a-
bly in luenced when applying he HIP ea men . As a esul o he L-PBF p ocess, a ine
mic os uc u e de eloped in a ma ensi ic (α’) needle shape due o he apid usion and
pos e io solidi ica ion (Figu e 5a,c). Howe e , a e he HIP he mal ea men a 920 °C,
below he β ansus (955 °C) empe a u e, he ine ma ensi ic mic os uc u e ans o med
in o a mix u e o α and β phases, whe e he α phase p esen s as ine pla es (Figu e 5b,d).
HIP ea men also induced a coa sening o he mic os uc u e compa ed o he o iginal
α’.
(a) (b)
J. Manu . Ma e . P ocess. 2023, 7, x FOR PEER REVIEW 8 o 21
(c) (d)
Figu e 5. FE-SEM mic og aphs o Ti6Al4V samples: (a,c) as-buil s a e and (b,d) HIP condi ion.
3.2. S a ic Mechanical P ope ies
Enginee ing s ess–s ain cu es and esul ing ensile p ope ies a e shown in Figu e
6 and Table 2, espec i ely, o as-buil and HIPed Ti6Al4V samples. The highes mechan-
ical s eng h was ob ained o samples in he as-buil condi ion, eaching app oxima ely
1260 MPa. Following HIP ea men , he s eng h was educed o a ound 942 MPa. Con-
ce ning duc ili y, as-buil pa s had a low elonga ion a ailu e o abou 8.5%. This alue
could be inc eased up o 12.5% wi h he HIP cycle. Consequen ly, HIP ea men a o s
he duc ili y o i anium pa s manu ac u ed by L-PBF.
Figu e 6. Enginee ing s ess–s ain cu es o he as-buil condi ion and o samples wi h HIP ea -
men .
Table 2. Tensile p ope ies o samples in he as-buil s a e (non-hea - ea ed) and a e applying HIP
ea men .
Sample σy (MPa) UTS (MPa) ε (%)
As-buil 1105 ± 8.3 1259 ± 9.6 8.5 ± 0.2
HIP 920 °C 942 ± 4.9 1019 ± 4.2 12.5 ± 0.3
3.3. Su ace T ea men o Fa igue Samples
The oughness o he as-buil su ace was measu ed be o e he applica ion o he di -
e en su ace ea men s. Ra ( he a e age oughness o he su ace) was 8.3 ± 0.9 µm.
Figu e 5. FE-SEM mic og aphs o Ti6Al4V samples: (a,c) as-buil s a e and (b,d) HIP condi ion.
J. Manu . Ma e . P ocess. 2023,7, 119 8 o 21
3.2. S a ic Mechanical P ope ies
Enginee ing s ess–s ain cu es and esul ing ensile p ope ies a e shown in Figu e 6
and Table 2, espec i ely, o as-buil and HIPed Ti6Al4V samples. The highes mechani-
cal s eng h was ob ained o samples in he as-buil condi ion, eaching app oxima ely
1260 MPa. Following HIP ea men , he s eng h was educed o a ound 942 MPa. Con-
ce ning duc ili y, as-buil pa s had a low elonga ion a ailu e o abou 8.5%. This alue
could be inc eased up o 12.5% wi h he HIP cycle. Consequen ly, HIP ea men a o s he
duc ili y o i anium pa s manu ac u ed by L-PBF.
J. Manu . Ma e . P ocess. 2023, 7, x FOR PEER REVIEW 8 o 21
(c) (d)
Figu e 5. FE-SEM mic og aphs o Ti6Al4V samples: (a,c) as-buil s a e and (b,d) HIP condi ion.
3.2. S a ic Mechanical P ope ies
Enginee ing s ess–s ain cu es and esul ing ensile p ope ies a e shown in Figu e
6 and Table 2, espec i ely, o as-buil and HIPed Ti6Al4V samples. The highes mechan-
ical s eng h was ob ained o samples in he as-buil condi ion, eaching app oxima ely
1260 MPa. Following HIP ea men , he s eng h was educed o a ound 942 MPa. Con-
ce ning duc ili y, as-buil pa s had a low elonga ion a ailu e o abou 8.5%. This alue
could be inc eased up o 12.5% wi h he HIP cycle. Consequen ly, HIP ea men a o s
he duc ili y o i anium pa s manu ac u ed by L-PBF.
Figu e 6. Enginee ing s ess–s ain cu es o he as-buil condi ion and o samples wi h HIP ea -
men .
Table 2. Tensile p ope ies o samples in he as-buil s a e (non-hea - ea ed) and a e applying HIP
ea men .
Sample σy (MPa) UTS (MPa) ε (%)
As-buil 1105 ± 8.3 1259 ± 9.6 8.5 ± 0.2
HIP 920 °C 942 ± 4.9 1019 ± 4.2 12.5 ± 0.3
3.3. Su ace T ea men o Fa igue Samples
The oughness o he as-buil su ace was measu ed be o e he applica ion o he di -
e en su ace ea men s. Ra ( he a e age oughness o he su ace) was 8.3 ± 0.9 µm.
Figu e 6.
Enginee ing s ess–s ain cu es o he as-buil condi ion and o samples wi h HIP ea men .
Table 2.
Tensile p ope ies o samples in he as-buil s a e (non-hea - ea ed) and a e applying
HIP ea men .
Sample σy(MPa) UTS (MPa) ε(%)
As-buil 1105 ±8.3 1259 ±9.6 8.5 ±0.2
HIP 920 ◦C 942 ±4.9 1019 ±4.2 12.5 ±0.3
3.3. Su ace T ea men o Fa igue Samples
The oughness o he as-buil su ace was measu ed be o e he applica ion o he
di e en su ace ea men s. Ra ( he a e age oughness o he su ace) was 8.3
±
0.9
µ
m.
Figu e 7shows oughness alues measu ed on pos -p ocessed su aces a e he di e se
su ace modi ica ion me hods. Compa ing he oughness o as-buil samples wi h he
ones ob ained wi h any o he su ace ea men s, i can be obse ed ha his alue was
conside ably educed. Among pos -p ocessing ea men s, blas ing modi ica ion ga e
ise o he oughes su ace, achie ing Ra o 1.94
±
0.14
µ
m. Subsequen elec opolishing
imp o ed he su ace condi ion, educing he oughness down o 1
µ
m (0.93
±
0.13
µ
m). In
he case o he ibo inishing su ace ea men , bo h condi ions led o oughness alues
below 1
µ
m. Op imizing ibo inishing condi ions, oughness was dec eased by hal , om
0.77
±
0.21
µ
m o 0.31
±
0.10
µ
m. Finally, he machined su ace was qui e simila o
ha ob ained wi h he ibo inishing me hod using op imized condi ions. Howe e , he
oughness is mo e homogeneous and he obse ed de ia ion is smalle .
J. Manu . Ma e . P ocess. 2023,7, 119 9 o 21
J. Manu . Ma e . P ocess. 2023, 7, x FOR PEER REVIEW 9 o 21
Figu e 7 shows oughness alues measu ed on pos -p ocessed su aces a e he di e se
su ace modi ica ion me hods. Compa ing he oughness o as-buil samples wi h he ones
ob ained wi h any o he su ace ea men s, i can be obse ed ha his alue was con-
side ably educed. Among pos -p ocessing ea men s, blas ing modi ica ion ga e ise o
he oughes su ace, achie ing Ra o 1.94 ± 0.14 µm. Subsequen elec opolishing im-
p o ed he su ace condi ion, educing he oughness down o 1 µm (0.93 ± 0.13 µm). In
he case o he ibo inishing su ace ea men , bo h condi ions led o oughness alues
below 1 µm. Op imizing ibo inishing condi ions, oughness was dec eased by hal , om
0.77 ± 0.21 µm o 0.31 ± 0.10 µm. Finally, he machined su ace was qui e simila o ha
ob ained wi h he ibo inishing me hod using op imized condi ions. Howe e , he
oughness is mo e homogeneous and he obse ed de ia ion is smalle .
In Figu es 8 and 9, he opog aphy o he su aces in each condi ion is de ailed. As-
ab ica ed pa s exhibi ed pa ially mel ed pa icles on he su ace (a), being esponsible
o he esul an ough su ace. The su ace opog aphy o he samples ea ed wi h he
applied me hods was ans o med signi ican ly. Machined su aces (b) look smoo h, al -
hough some machining pa allel ma ks can be seen by con ocal mic oscopy. Wi h blas ing
(c) and E-Blas ing (d), he pa ially mel ed powde pa icles we e emo ed comple ely.
Howe e , he su ace ea men wi h he blas ing me hod displayed peaks and alleys,
whe eas he E-Blas ed samples showed a smoo he and b igh e appea ance. As is e iden
in (e), he condi ions i s ied in he ibo inishing echnique we e no able o o ally elim-
ina e he pa ially mel ed pa icles, and impo an ca i ies we e le on he su ace. In-
c easing he ime o he p ocess, no pa ially mel ed pa icles we e obse ed, bu s ill,
some esidual ca i ies we e de ec ed ( ).
Figu e 7. Su ace oughness Ra o pos -p ocessed a igue sample.
(a) (b)
Figu e 7. Su ace oughness Ra o pos -p ocessed a igue sample.
In Figu es 8and 9, he opog aphy o he su aces in each condi ion is de ailed. As-
ab ica ed pa s exhibi ed pa ially mel ed pa icles on he su ace (a), being esponsible o
he esul an ough su ace. The su ace opog aphy o he samples ea ed wi h he applied
me hods was ans o med signi ican ly. Machined su aces (b) look smoo h, al hough
some machining pa allel ma ks can be seen by con ocal mic oscopy. Wi h blas ing (c) and
E-Blas ing (d), he pa ially mel ed powde pa icles we e emo ed comple ely. Howe e ,
he su ace ea men wi h he blas ing me hod displayed peaks and alleys, whe eas he
E-Blas ed samples showed a smoo he and b igh e appea ance. As is e iden in (e), he
condi ions i s ied in he ibo inishing echnique we e no able o o ally elimina e he
pa ially mel ed pa icles, and impo an ca i ies we e le on he su ace. Inc easing he
ime o he p ocess, no pa ially mel ed pa icles we e obse ed, bu s ill, some esidual
ca i ies we e de ec ed ( ).
Residual s ess analyses we e pe o med on he su aces o samples wi h and wi hou
su ace ea men s. I mus be no ed ha esidual s esses we e measu ed a e subjec ing
he samples o he HIP ea men . The measu emen esul s a e gi en in Figu e 10. Wi hou
su ace ea men , ha is, in he as-HIPed s a e, ensile s esses we e appa en . A e
su ace- ea ing he samples, ensile s esses we e con e ed in o comp essi e esidual
s esses, i espec i e o he ype o su ace modi ica ion echnique employed. The highes
comp essi e esidual s esses we e measu ed o he blas ed and op imized ibo inished
ea men s, ollowed by machined samples and ibo inishing applied wi h he ini ial
p ocessing condi ions. I was also obse ed ha elec opolishing educes he le el o
esidual comp essi e s esses in compa ison wi h he blas ed samples. In ac , he E-Blas ed
sample is he one wi h he lowes esidual comp essi e s ess, app oaching ze o.
J. Manu . Ma e . P ocess. 2023, 7, x FOR PEER REVIEW 9 o 21
Figu e 7 shows oughness alues measu ed on pos -p ocessed su aces a e he di e se
su ace modi ica ion me hods. Compa ing he oughness o as-buil samples wi h he ones
ob ained wi h any o he su ace ea men s, i can be obse ed ha his alue was con-
side ably educed. Among pos -p ocessing ea men s, blas ing modi ica ion ga e ise o
he oughes su ace, achie ing Ra o 1.94 ± 0.14 µm. Subsequen elec opolishing im-
p o ed he su ace condi ion, educing he oughness down o 1 µm (0.93 ± 0.13 µm). In
he case o he ibo inishing su ace ea men , bo h condi ions led o oughness alues
below 1 µm. Op imizing ibo inishing condi ions, oughness was dec eased by hal , om
0.77 ± 0.21 µm o 0.31 ± 0.10 µm. Finally, he machined su ace was qui e simila o ha
ob ained wi h he ibo inishing me hod using op imized condi ions. Howe e , he
oughness is mo e homogeneous and he obse ed de ia ion is smalle .
In Figu es 8 and 9, he opog aphy o he su aces in each condi ion is de ailed. As-
ab ica ed pa s exhibi ed pa ially mel ed pa icles on he su ace (a), being esponsible
o he esul an ough su ace. The su ace opog aphy o he samples ea ed wi h he
applied me hods was ans o med signi ican ly. Machined su aces (b) look smoo h, al -
hough some machining pa allel ma ks can be seen by con ocal mic oscopy. Wi h blas ing
(c) and E-Blas ing (d), he pa ially mel ed powde pa icles we e emo ed comple ely.
Howe e , he su ace ea men wi h he blas ing me hod displayed peaks and alleys,
whe eas he E-Blas ed samples showed a smoo he and b igh e appea ance. As is e iden
in (e), he condi ions i s ied in he ibo inishing echnique we e no able o o ally elim-
ina e he pa ially mel ed pa icles, and impo an ca i ies we e le on he su ace. In-
c easing he ime o he p ocess, no pa ially mel ed pa icles we e obse ed, bu s ill,
some esidual ca i ies we e de ec ed ( ).
Figu e 7. Su ace oughness Ra o pos -p ocessed a igue sample.
(a) (b)
Figu e 8. Con .
J. Manu . Ma e . P ocess. 2023,7, 119 16 o 21
J. Manu . Ma e . P ocess. 2023, 7, x FOR PEER REVIEW 17 o 21
(i) (j)
(k)
Figu e 13. F ac u e su aces o a igue samples a e (a,b) blas ing, (c,d) E-Blas ing, (e) E-Blas ing
ocused on su ace ca i y, ( ,g) ibo inishing (ini ial condi ions), (h,i) ibo inishing (op imized con-
di ions) and (j,k) machined. Red squa es indica e c ack ini ia ion si es while black a ows c ack
g ow h di ec ion.
As explained p e iously, he a igue c ack was ini ia ed om de ec s ound on he
samples’ su aces ega dless o he ype o su ace ea men applied. Fo ins ance, he
ca i ies ha o igina ed in E-Blas ed samples a e s ess concen a o s ha ini ia e c acks
(Figu e 13e). Figu e 13d shows he c ack ini ia ion si e ( ed ec angle) in addi ion o he
a igue c ack g ow h di ec ion (black a ows). Fu he magni ica ion o he a ea a ound
he c ack ini ia ion si e (Figu e 14a) e eals ha he ac u e is gene ally domina ed by
ansg anula ac u e mechanisms, whe e he ac u e akes place h ough he g ains. In-
s ead, he mic og aph co esponding o he a ea a om he c ack ini ia ion si e (Figu e
14b) indica es ha in he las s ages, he ac u e occu s by in e g anula mechanisms, in
which he c ack p opaga es along g ain bounda ies. Simila beha io was obse ed o
he es o he su ace ea men s.
(a) (b)
Figu e 14. F ac u e su aces o a igue samples a e E-Blas ing. (a) A ea close o he c ack ini ia ion
si e and (b) a ea a om he c ack ini ia ion si e.
Figu e 13.
F ac u e su aces o a igue samples a e (
a
,
b
) blas ing, (
c
,
d
) E-Blas ing, (
e
) E-Blas ing
ocused on su ace ca i y, (
,
g
) ibo inishing (ini ial condi ions), (
h
,
i
) ibo inishing (op imized
condi ions) and (
j
,
k
) machined. Red squa es indica e c ack ini ia ion si es while black a ows c ack
g ow h di ec ion.
T ibo inishing ea men is also able o in oduce comp essi e esidual s esses on he
su ace which a e highe when op imized condi ions a e employed and compa able o
he blas ing p ocess. Howe e , using ibo inishing, a igue is imp o ed wi h espec o
he blas ing condi ion. The esul ing su aces a e smoo he han hose ob ained wi h he
p e iously men ioned ea men s, whe e e y low oughness alues a e measu ed, espe-
cially wi h he op imized condi ion. The educ ion in oughness om ini ial ibo inishing
condi ions o he op imized ones p oduces be e a igue p ope ies. Possibly a g ea e
imp o emen in a igue esponse would be obse ed i su ace i egula i ies we e a oided.
Nume ous and la ge su ace ca i ies can be ound using ini ial condi ions which a e accom-
panied by de o med powde pa icles. These de ec s a e educed conside ably when he
samples a e ea ed wi h op imized condi ions. Again, o bo h ibo inishing condi ions,
he up u e occu s on he su ace (Figu e 13
−
i). Simila ca i ies we e ound in [
14
] bu
a e subjec ing he samples o we polishing. The a igue esul s a e supe io o hose
ob ained wi h ibo inishing. Ne e heless, he dis ibu ion and numbe o ca i ies emain
unknown o a e no speci ied by he au ho s. Addi ionally, he e is a lack o in o ma ion
ega ding esidual s esses.
The measu ed oughness alue in machined samples is he lowes and compa able o
he oughness ob ained wi h ibo inishing in op imized condi ions. The di e ence be ween
hese wo su ace inishing me hods lies in he oughness homogenei y along he whole
su ace. Machined su aces do no show i egula i ies as is he case o ibo inishing. This
ac is also demons a ed by he much smalle de ia ion obse ed in oughness measu e-
men s (Figu e 7) o machined samples. Machining also p oduces a o able comp essi e
esidual s esses, whe e in e media e alues be ween he wo ibo inished condi ions a e
achie ed. Consequen ly, machining p oduces he bes a igue esul s. The c ack ini ia ion
si e is loca ed a he su ace, as shown in Figu e 13 . This is consis en wi h he conclusions
ex ac ed by [
38
] ega ding he ac u e su ace analysis o samples es ed below 10
7
cycles.
J. Manu . Ma e . P ocess. 2023,7, 119 17 o 21
As explained p e iously, he a igue c ack was ini ia ed om de ec s ound on he
samples’ su aces ega dless o he ype o su ace ea men applied. Fo ins ance, he
ca i ies ha o igina ed in E-Blas ed samples a e s ess concen a o s ha ini ia e c acks
(Figu e 13e). Figu e 13d shows he c ack ini ia ion si e ( ed ec angle) in addi ion o he
a igue c ack g ow h di ec ion (black a ows). Fu he magni ica ion o he a ea a ound he
c ack ini ia ion si e (Figu e 14a) e eals ha he ac u e is gene ally domina ed by ans-
g anula ac u e mechanisms, whe e he ac u e akes place h ough he g ains. Ins ead,
he mic og aph co esponding o he a ea a om he c ack ini ia ion si e (Figu e 14b)
indica es ha in he las s ages, he ac u e occu s by in e g anula mechanisms, in which
he c ack p opaga es along g ain bounda ies. Simila beha io was obse ed o he es o
he su ace ea men s.
J. Manu . Ma e . P ocess. 2023, 7, x FOR PEER REVIEW 17 o 21
(i) (j)
(k)
Figu e 13. F ac u e su aces o a igue samples a e (a,b) blas ing, (c,d) E-Blas ing, (e) E-Blas ing
ocused on su ace ca i y, ( ,g) ibo inishing (ini ial condi ions), (h,i) ibo inishing (op imized con-
di ions) and (j,k) machined. Red squa es indica e c ack ini ia ion si es while black a ows c ack
g ow h di ec ion.
As explained p e iously, he a igue c ack was ini ia ed om de ec s ound on he
samples’ su aces ega dless o he ype o su ace ea men applied. Fo ins ance, he
ca i ies ha o igina ed in E-Blas ed samples a e s ess concen a o s ha ini ia e c acks
(Figu e 13e). Figu e 13d shows he c ack ini ia ion si e ( ed ec angle) in addi ion o he
a igue c ack g ow h di ec ion (black a ows). Fu he magni ica ion o he a ea a ound
he c ack ini ia ion si e (Figu e 14a) e eals ha he ac u e is gene ally domina ed by
ansg anula ac u e mechanisms, whe e he ac u e akes place h ough he g ains. In-
s ead, he mic og aph co esponding o he a ea a om he c ack ini ia ion si e (Figu e
14b) indica es ha in he las s ages, he ac u e occu s by in e g anula mechanisms, in
which he c ack p opaga es along g ain bounda ies. Simila beha io was obse ed o
he es o he su ace ea men s.
(a) (b)
Figu e 14. F ac u e su aces o a igue samples a e E-Blas ing. (a) A ea close o he c ack ini ia ion
si e and (b) a ea a om he c ack ini ia ion si e.
Figu e 14. F ac u e su aces o a igue samples a e E-Blas ing. (a) A ea close o he c ack ini ia ion
si e and (b) a ea a om he c ack ini ia ion si e.
Figu e 15 shows a anking o su ace p ope ies o samples wi h he analyzed su ace
ea men s, cons uc ed by di e en onali ies o a ce ain colo . Wi hin a p ope y, he
da kes onali y signi ies he wo s alue achie ed and a high (nega i e) impac on a igue
esul s. Fa igue has also been anked using he same colo code. I is e iden ha when
oughness is educed, a igue is imp o ed acco dingly. Rega ding opog aphy, he smoo he
he su ace is, he be e he a igue beha io . Addi ionally, i is wo h ema king ha su ace
i egula i ies should be a oided o bene i om a smoo h su ace. Finally, when i comes
o su ace esidual s esses, hese should be as comp essi e as possible o ha e a posi i e
impac on a igue. Ne e heless, his posi i e e ec is coun e ac ed when he oughness is
oo high. This is he case o he su ace blas ing me hod. The e o e, oughness seems o be
he mos c i ical su ace p ope y o a igue beha io . Chan e al. [
39
] also deduced ha he
mean a igue li e o Ti6Al4V dec eases wi h inc easing maximum oughness o he su ace
ea u es due o s ess concen a ions a hese poin s. I has been demons a ed ha he
ibo inishing me hod has signi ican po en ial in imp o ing he su ace oughness, bu s ill,
a igue s eng h is no as high as in he machined condi ion. As depic ed in Figu e 16, all
he es ed su ace ea men s gi e ise o a igue p ope ies compa able o hose achie ed
by cas ing wi h HIP Ti6Al4V ma e ial. Only he a igue s eng h o machined samples is
compa able o con en ional w ough ma e ial.
J. Manu . Ma e . P ocess. 2023, 7, x FOR PEER REVIEW 18 o 21
Figu e 15 shows a anking o su ace p ope ies o samples wi h he analyzed su ace
ea men s, cons uc ed by di e en onali ies o a ce ain colo . Wi hin a p ope y, he
da kes onali y signi ies he wo s alue achie ed and a high (nega i e) impac on a igue
esul s. Fa igue has also been anked using he same colo code. I is e iden ha when
oughness is educed, a igue is imp o ed acco dingly. Rega ding opog aphy, he
smoo he he su ace is, he be e he a igue beha io . Addi ionally, i is wo h ema k-
ing ha su ace i egula i ies should be a oided o bene i om a smoo h su ace. Finally,
when i comes o su ace esidual s esses, hese should be as comp essi e as possible o
ha e a posi i e impac on a igue. Ne e heless, his posi i e e ec is coun e ac ed when
he oughness is oo high. This is he case o he su ace blas ing me hod. The e o e,
oughness seems o be he mos c i ical su ace p ope y o a igue beha io . Chan e al.
[39] also deduced ha he mean a igue li e o Ti6Al4V dec eases wi h inc easing maxi-
mum oughness o he su ace ea u es due o s ess concen a ions a hese poin s. I has
been demons a ed ha he ibo inishing me hod has signi ican po en ial in imp o ing
he su ace oughness, bu s ill, a igue s eng h is no as high as in he machined condi-
ion. As depic ed in Figu e 16, all he es ed su ace ea men s gi e ise o a igue p op-
e ies compa able o hose achie ed by cas ing wi h HIP Ti6Al4V ma e ial. Only he a-
igue s eng h o machined samples is compa able o con en ional w ough ma e ial.
Figu e 15. Colo -based anking o su ace p ope ies and a igue beha io as a unc ion o he ap-
plied su ace ea men .
Figu e 16. Fa igue pe o mance o addi i ely manu ac u ed and su ace- ea ed Ti6Al4V samples
and compa ison wi h con en ional Ti6Al4V ma e ials.
5. Conclusions
In his s udy, he a igue beha io o Ti6Al4V alloys p ocessed by L-PBF is p esen ed,
wi h pa icula emphasis on he su ace oughness, esidual s esses and opog aphy. The
Figu e 15.
Colo -based anking o su ace p ope ies and a igue beha io as a unc ion o he applied
su ace ea men .
J. Manu . Ma e . P ocess. 2023,7, 119 18 o 21
J. Manu . Ma e . P ocess. 2023, 7, x FOR PEER REVIEW 18 o 21
Figu e 15 shows a anking o su ace p ope ies o samples wi h he analyzed su ace
ea men s, cons uc ed by di e en onali ies o a ce ain colo . Wi hin a p ope y, he
da kes onali y signi ies he wo s alue achie ed and a high (nega i e) impac on a igue
esul s. Fa igue has also been anked using he same colo code. I is e iden ha when
oughness is educed, a igue is imp o ed acco dingly. Rega ding opog aphy, he
smoo he he su ace is, he be e he a igue beha io . Addi ionally, i is wo h ema k-
ing ha su ace i egula i ies should be a oided o bene i om a smoo h su ace. Finally,
when i comes o su ace esidual s esses, hese should be as comp essi e as possible o
ha e a posi i e impac on a igue. Ne e heless, his posi i e e ec is coun e ac ed when
he oughness is oo high. This is he case o he su ace blas ing me hod. The e o e,
oughness seems o be he mos c i ical su ace p ope y o a igue beha io . Chan e al.
[39] also deduced ha he mean a igue li e o Ti6Al4V dec eases wi h inc easing maxi-
mum oughness o he su ace ea u es due o s ess concen a ions a hese poin s. I has
been demons a ed ha he ibo inishing me hod has signi ican po en ial in imp o ing
he su ace oughness, bu s ill, a igue s eng h is no as high as in he machined condi-
ion. As depic ed in Figu e 16, all he es ed su ace ea men s gi e ise o a igue p op-
e ies compa able o hose achie ed by cas ing wi h HIP Ti6Al4V ma e ial. Only he a-
igue s eng h o machined samples is compa able o con en ional w ough ma e ial.
Figu e 15. Colo -based anking o su ace p ope ies and a igue beha io as a unc ion o he ap-
plied su ace ea men .
Figu e 16. Fa igue pe o mance o addi i ely manu ac u ed and su ace- ea ed Ti6Al4V samples
and compa ison wi h con en ional Ti6Al4V ma e ials.
5. Conclusions
In his s udy, he a igue beha io o Ti6Al4V alloys p ocessed by L-PBF is p esen ed,
wi h pa icula emphasis on he su ace oughness, esidual s esses and opog aphy. The
Figu e 16.
Fa igue pe o mance o addi i ely manu ac u ed and su ace- ea ed Ti6Al4V samples
and compa ison wi h con en ional Ti6Al4V ma e ials.
5. Conclusions
In his s udy, he a igue beha io o Ti6Al4V alloys p ocessed by L-PBF is p esen ed,
wi h pa icula emphasis on he su ace oughness, esidual s esses and opog aphy. The
in luences o a ious su ace ea men s such as mechanical, elec ochemical and hei
combina ion ha e been conside ed o imp o e a igue beha io . Fu he , he mic os uc u e
and ensile p ope ies in di e en hea - ea ed s a es ha e been ho oughly analyzed. The
key indings can be summa ized as ollows:
•
De ec s a e mo e c i ical o a igue han duc ili y. Con en ionally hea - ea ed and
HIPed samples show a simila mic os uc u e composed o
α
+
β
phases, he la e
wi h minimized po osi y;
•
HIP has been ound no o be o ally e ec i e in emo ing su ace esidual s esses.
The e a e emaining ensile esidual s esses which a e con e ed o comp essi e a e
applying he su ace ea men s;
•
All he s udied su ace modi ica ion me hods a e e ec i e in educing oughness.
T ibo inishing leads o he maximum oughness educ ion, 97%, simila o machining
inishing;
•
Al hough ibo inishing signi ican ly educed he oughness and achie ed a alue well
below 1
µ
m, he a igue esponse is no compa able o ha ob ained wi h machining
due o he i egula i ies ound on he su ace. I would be equi ed o op imize he
ibo inishing p ocess e en u he in o de o ob ain comple ely smoo h su aces;
•
I appea s ha o a igue, oughness is he mos c i ical su ace p ope y, mo e han
he in oduced comp essi e esidual s esses. This is e iden in blas ed samples. High
comp essi e esidual s esses a e in oduced when blas ing, bu he high oughness
p omo es he p ema u e ailu e o he samples;
•
The subsequen elec opolishing applied o blas ed samples (E-Blas ing ea men )
educes he su ace oughness and he le el o in oduced comp essi e esidual s esses
by he blas ing p ocess. Due o he comp essi e na u e o he esidual s esses and he
low oughness achie ed, a igue is imp o ed compa ed o he blas ed samples;
•Low oughness alues and comp essi e esidual s esses a o a igue esponse;
•
All he samples ac u e om he su ace; he e a e no in e nal c i ical de ec s due o
he applica ion o HIP ea men . The i egula i ies ound in he o m o ca i ies o
pi s a e s ess concen a o s ha ini ia e c acks;
J. Manu . Ma e . P ocess. 2023,7, 119 19 o 21
•
I has been demons a ed ha he a igue p ope ies o he samples wi h he applied
su ace ea men s a e compa able o he cas ing ma e ial, excep o he machined
samples, which show he bes a igue p ope ies, compa able o he con en ional
Ti6Al4V w ough ma e ial. Thus, machining could be subs i u ed by hese me hods
o applica ions wi h lowe equi emen s;
•
I would be in e es ing o analyze he elec opolishing me hod by i sel , imp o ing he
su ace oughness educ ion, o e i y i s capabili y o e en imp o e he esul s since
i could be an op ion o addi i e complex pa s whe e mechanical ea men s such as
machining o ibo inishing a e no possible o use.
Au ho Con ibu ions:
Concep ualiza ion, A.M.M., M.B.G.-B. and P.J.A.; me hodology, M.B.G.-B.,
E.E., M.C. and F.G.; so wa e, F.G.; alida ion, J.A.; in es iga ion, I.Q., E.E., M.C., J.A. and F.G.; da a
cu a ion, M.C.; w i ing—o iginal d a p epa a ion, A.M.M.; w i ing— e iew and edi ing, A.M.M.,
M.B.G.-B., I.Q., P.J.A. and M.C.; supe ision, A.M.M., M.B.G.-B., I.Q. and P.J.A.; p ojec adminis a ion,
A.M.M.; unding acquisi ion, A.M.M., M.B.G.-B., I.Q. and P.J.A. All au ho s ha e ead and ag eed o
he published e sion o he manusc ip .
Funding:
This esea ch was unded by he Depa amen o de Desa ollo Económico, Sos enibilidad
y Medio Ambien e o he Basque Go e nmen (ELKARTEK 2022 KK-2022/00070), by he Depa a-
men o de Desa ollo Económico y Compe i i idad o he Basque Go e nmen (ELKARTEK 2019
KK-2019/00077) and by he Eu opean Union (p ojec TIFAN, JTI-CS-2013-1-ECO-01-066).
Da a A ailabili y S a emen :
The esea ch da a p esen ed in his s udy a e a ailable on eques om
he co esponding au ho .
Con lic s o In e es : The au ho s decla e no con lic o in e es .
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