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Chemical and microstructural characterization of (Y or Zr)-doped CrAlN coatings

Abstract

Magnetron sputtered chromium aluminium nitride films are excellent candidates for advanced machining and protection for high temperature applications. In this work CrAlN-based coatings including Y or Zr as dopants (≈ 2 at.%) are deposited by d.c. reactive magnetron sputtering on silicon substrates using metallic targets and Ar/N2 mixtures. The hardness properties are found in the range of 22–33 GPa with H/E ratios close to 0.1. The influence of the dopant element in terms of oxidation resistance after heating in air at 1000 °C is studied by means of X-ray diffraction (XRD), cross-sectional scanning electron microscopy (X-SEM) and energy dispersive X-ray analysis (EDX). The microstructure and chemical bonding are investigated using a transmission electron microscope (TEM) and electron energy-loss spectroscopy (EELS) respectively. The improvement in oxidation resistance as compared to pure CrN coating is manifested in the formation of a Al-rich outer layer that protects the underneath coating from oxygen diffusion. The best performance obtained with the CrAlYN film is investigated by in situ annealing of this sample inside the TEM in order to gain knowledge about the structural and chemical transformations induced during heating.

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Chemical and microstructural characterization of (Y or Zr)-doped CrAlN coatings

Author: Rojas Ruiz, Teresa Cristina; El Mrabet, Said; Domínguez Meister, Santiago; Brizuela, Marta; García Luis, Alberto; Sánchez López, Juan Carlos
Publisher: Elsevier
Year: 2012
DOI: 10.1016/j.surfcoat.2011.07.071
Source: https://idus.us.es/bitstreams/e66a12db-b897-4bf5-a6cd-d9ccb5834805/download
1
Chemical and mic os uc u al cha ac e iza ion o (Y o Z )-doped C AlN
coa ings
T.C. Rojasa, S. El M abe a, S. Domínguez-Meis e a, M. B izuelab, A. Ga cía-Luisb, J.C.
Sánchez-Lópeza
aIns i u o de Ciencia de Ma e iales de Se illa (CSIC-Uni . Se illa), A da. Amé ico Vespucio
49, 41092-Se illa, Spain
bTECNALIA, Mikele egui Pasealekua, 2
20009 Donos ia-San Sebas ián, Spain
Abs ac
Magne on spu e ed ch omium aluminium ni ide ilms a e excellen candida es o
ad anced machining and p o ec ion o high empe a u e applica ions. In his wo k C AlN-
based coa ings including Y o Z as dopan s (2 a . %) a e deposi ed by d.c. eac i e
magne on spu e ing on silicon subs a es using me allic a ge s and A /N2 mix u es. The
ha dness p ope ies a e ound in he ange o 22-33 GPa wi h H/E a ios close o 0.1. The
in luence o he dopan elemen in e ms o oxida ion esis ance a e hea ing in ai a 1000ºC
is s udied by means o X- ay di ac ion (XRD), c oss-sec ional scanning elec on
mic oscopy (X-SEM) and ene gy dispe si e X- ay analysis (EDAX). The mic os uc u e and
chemical bonding a e in es iga ed using a ansmission elec on mic oscope (TEM) and
elec on ene gy-loss spec oscopy (EELS) espec i ely. The imp o emen in oxida ion
esis ance as compa ed o pu e C N coa ing is mani es ed in he o ma ion o a Al- ich ou e
laye ha p o ec s he unde nea h coa ing om oxygen di usion. The bes pe o mance
ob ained wi h he C AlYN ilm is in es iga ed by in si u annealing o his sample inside he
TEM in o de o gain knowledge abou he s uc u al and chemical ans o ma ions induced
du ing hea ing.
*Manusc ip wi h changes highligh ed
Click he e o iew linked Re e ences
2
1. In oduc ion
C 1-xAlxN ilms deposi ed by physical apou deposi ion ha e p o en o be e ec i e
p o ec i e coa ings o machining applica ions and a e p omising candida es o a ious o he
high empe a u e applica ions [1-7]. The inco po a ion o Al o C N esul s in highe
ha dness, he mal and chemical s abili y, allowing inc eased e iciency o cu ing and o ming
ools [8,9]. The concen a ion o Al inside he coa ing is ied o be con olled below 70 mol
% in o de o o m he me as able solid solu ion o Al inside he cc C N la ice [10,11]. The
o ma ion o hexagonal AlN s uc u e usually exhibi s lowe ha dness and elas ic moduli,
which esul s in lowe wea esis ance. When exposed o ai a ele a ed empe a u es, C 1-
xAlxN ilms o m dense and adhe en mixed aluminium and ch omium oxide scales [1,8,12],
which e en ually supp ess he oxygen di usion in o he bulk, p o iding excellen oxida ion
esis ance up o empe a u es as high as 900ºC [13-15]. Cu en in es iga ions seek o
imp o e he he mal and oxida ion esis ance abo e his limi empe a u e by inco po a ion o
la ge (subs i u ional) a oms, as hey e ec i ely e a d di usion ela ed p ocesses ( eco e y,
decomposi ion and ec ys alliza ion). Y ium has been p oposed o be e ec i e o his
pu pose by seg ega ion o he oxide scale g ain bounda ies, blocking as di usion pa hs and
inc easing he onse o decomposi ion o 1100ºC [16-20]. Mo eo e , he addi ion o a
eac i e elemen was sugges ed o educe he accumula ion o oids a he subs a e/scale
in e ace [21] o o imp o e he mechanical p ope ies o he scale by modi ying he oxide
scale s uc u e [22]. In p e ious wo ks [4,5] we ha e shown he inc emen o he oxida ion
esis ance o a C AlN coa ing abo e 800 °C. In iew o he bene icial e ec s o Y, he p esen
wo k was unde aken o in es iga e he p ospec o adding Y o a simila C AlN coa ing o
imp o e he oxida ion beha iou . Besides, in an a emp o es ablish some undamen al
unde s anding on he oxida ion mechanism, ano he la ge subs i u ional a om like Z is
inco po a ed ins ead o Y a simila concen a ion o check he in luence o he ype o dopan .
3
2. Expe imen al de ails
C Al(Y,Z )N coa ings we e p epa ed on Si (100) subs a es by dc magne on spu e ing
using A /N2 mix u es in a comme cial equipmen (CemeCon® CC800/8) p o ided wi h ou
ec angula a ge s (200 mm  88 mm  5 mm): wo o ch omium (99.9% pu i y), one o
aluminum (99.5% pu i y) and he las one ei he o y ium o zi conium (99.5% pu i y). The
base p essu e o he acuum chambe was 110−4 Pa and he wo king p essu e se a 1 Pa,
wi h a A /N2 a io o 1.5. The spu e ing condi ions we e se o 3000 W o he ch omium and
aluminium and 1500 W o Y o Z a ge s. The sample holde was nega i ely biased in he
ange o 110–120 V and he empe a u e anged om 200 o 400 °C due o plasma hea ing
e ec .
Chemical composi ion o he samples was ob ained by elec on p obe mic oanalysis
(EPMA). The EPMA equipmen was a JEOL JXA-8200 Supe P obe ins umen equipped
wi h ou wa eleng hs de ec o s (WDS) and one ene gy-dispe si e X- ay (EDX). The X- ay
di ac ion pa e ns we e ob ained in a X´Pe P o PANALYTICAL di ac ome e in he
con en ional  B agg-B en ano con igu a ion using Cu K adia ion. The mo phology and
hickness o he coa ings was in es iga ed by scanning elec on mic oscopy (SEM) pe o med
in a high esolu ion FEG mic oscope, HITACHI-4800. Samples g own on silicon subs a es
we e clea ed o SEM c oss-sec ion examina ion. T ansmission elec on mic oscopy (TEM)
and elec on ene gy-loss spec oscopy (EELS) we e ca ied ou in a Philips CM20 mic oscope
ope a ing a 200 kV equipped wi h a PEELS spec ome e (Ga an). Fo he TEM obse a ion,
c oss sec ional specimens we e p epa ed in he con en ional manne by mechanical polishing
ollowed by A + ion milling o elec on anspa ency. The EELS da a we e acqui ed in he
di ac ion mode wi h a came a leng h o 470 mm, a 2-mm spec ome e en ance ape u e and
a collec ion angle o 1.45 m ad. These condi ions yielded an ene gy esolu ion a he ze o loss
peak o 1.2 eV. A e he sub ac ion o he backg ound and he decon olu ion o plu al
sca e ing, he spec a we e no malized o he jump. All o hese ea men s we e pe o med
4
wi hin he EL/P p og am (Ga an). The mechanical p ope ies we e measu ed wi h a
Fische scope H100 dynamic mic op obe ins umen using a con en ional Vicke s inden e a
loads up o 10 mN. The maximum load was selec ed in such a way ha he maximum
inden a ion dep h did no exceed 10–15% o he coa ing hickness in o de o a oid he
in luence o he subs a e.
3. Resul s and discussion
3.1. Chemical and mic os uc u al cha ac e iza ion
Table 1 summa izes he chemical composi ion ob ained by EPMA and ha dness and
Young’s modulus alues o he coa ings. The ha dness p ope ies a e ound in he ange o
22-33 GPa wi h H/E a ios close o 0.1. The mic oc ys alline s uc u e o he ou samples
unde s udy is shown in he B agg-B en ano XRD scans o Fig. 1. I can be seen ha he C N-
based coa ings exhibi he main peaks co esponding o C N calsbe gi e (JCPDS 01-076-
2494) al hough wi h di e en p e e ed o ien a ion and deg ee o c ys allini y depending on
he sample. The inco po a ion o me als (Al and Y o Z ) in o he C N la ice esul s in
b oade XRD peaks indica ing smalle c ys alline domains and change o ex u e. Thus, he
C AlZ N coa ing is less ex u ed, mo e simila o C N, wi h <111> p e e ed o ien a ion. In
he case o C AlN and C AlYN ilms, he p e e ed o ien a ions a e obse ed o shi o
<220> and <200> espec i ely.
Rep esen a i e c oss-sec ion SEM mic og aphs o he C N, C AlN, C AlZ N and C AlYN
ilms a e shown in Fig. 2. The ilm hickness alues ypically a y in he 2–3 μm ange o he
C AlN-based coa ings and 5.8 μm o C N. The exac alues a e included in he Table 1. A
ypical columna s uc u e is obse ed al hough ce ain di e ences in column wid h and
po osi y can be no iced. A mo e de ailed analysis by X-TEM allowed o de e mine he la e al
size o he columns being es ima ed in 80 nm o he C AlN sample, 60-70 nm o C AlZ N
and 100-110 nm o he C AlYN sample. These wid h alues co ela e wi h he measu ed
5
ha dness in he sense ha smalle columna sizes gene a e mo e compac s uc u es and
acco dingly highe ha dness p ope ies. Fig 3 shows a con en ional b igh ield X-TEM
image co esponding o he sample C AlYN as ep esen a i e example o he de eloped ilm
mic os uc u e. F om his pic u e i is clea ly no iced ha besides o he ypical columna
mic os uc u e along he g owing di ec ion a pe iodic laye ed s uc u e, pa allel o he
subs a e, is obse ed. This laye ed a chi ec u e is o med by indi idual laye s o di e en
hickness (20-30 nm he da ke laye and 4-8 nm he b igh e one). This pe iodic laye ed
s uc u e appea s in he h ee C AlN-based samples and could be ela ed o he con igu a ion
o he subs a es in espec o he magne on sou ces. Simila mul ilaye s uc u es ha e been
obse ed in ilms p epa ed by magne on spu e ing due o he o a ion o he samples
alongside he di e en a ge s [23,24]. The selec ed a ea elec on di ac ion (SAED) pa e n
ob ained o his coa ing is including as inse in Fig. 3. The p esence o di ac ion ings is
indica i e o he polyc ys alline na u e o he sample. The di ac ion ings can be assigned o
he planes (111), (002) and (220) co esponding o he cubic phase o C (Al)N phase.
Mo eo e , i is obse ed a ce ain p e e en ial o ien a ion o he c ys alli es o he (200) and
(111) planes along he g owing di ec ion.
In Fig. 4 a high- esolu ion ansmission elec on mic og aph ob ained om a c oss-sec ion
image o he C AlYN sample is p esen ed. The measu ed d-spacing o he la ice inges is 2.4
Å ha can be assigned o he (111) plane o cubic C (Al)N phase. The dashed and do ed lines
a e plo ed as eye-guide o indica e he sepa a ion be ween he columna and he mul ilaye
s uc u e espec i ely. I is wo h o men ioning he s uc u al c ys alline cohe ency exis ing
be ween he wo laye s wi h di e en con as abo emen ioned. The EELS analysis pe o med
in he TEM p epa a ions o he coa ings is a powe ul ool o de e mine he chemical bonding
s a e in nanos uc u ed and mul iphase sys ems [25]. The O-K, N-K and C -L2,3 spec a ha e
been measu ed o all he C AlN-based samples and compa ed o C N [26], C 2N and c-AlN
[27] e e ences compounds used as inge p in s. The hcp-AlN spec um is no conside ed as

6
he change o c ys al s uc u e o C 1-xAlxN om cubic o hexagonal appea s a x alues o
0.6-0.7 [10,11], much highe han hose shown by he coa ings unde s udy. The ine s uc u e
o he N-K edge is known o be sensi i e o he local a omic en i onmen and consequen ly i
can be used o iden i ica ion o he ch omium ni ides [26]. No O-K edge could be de ec ed
in none o he samples in ag eemen wi h he low alues o oxygen measu ed by EPMA (< 1
a . %). Fig. 5 depic s he no malized N-K and C -L2,3 edges spec a o he all he samples and
hose co esponding o he e e ence compounds. Some di e en ea u es can be highligh ed
by compa ison o he spec a. The N-K edge o ch omium ni ides show wo main ea u es a
abou 400 and 410 eV al hough hey di e in in ensi y. Thus, he second cha ac e is ic
esonance peak is less p onounced o he C 2N in compa ison o he C N. The edge onse o
he cubic o m o AlN appea s a highe ene gies, displaying he mos in ense ene gy-loss
peak a ound 407 eV. The ELNES s uc u e o he N-K edge o he h ee C (Al)N-based
coa ings is simila o he C N e e ence wi h he pa icula i ies o a diminu ion o he in ensi y
o he i s peak and he de ec ion o a small shoulde a 407 eV. These di e ences can be
a ibu ed o he Al inco po a ion in he C N phase and/o he o ma ion o AlN phases in he
coa ings. Ne e heless, acco ding o he low Al con en and p e ious published wo ks he
obse ed changes can be a he associa ed o he inco po a ion o Al inside he cubic C N
la ice o ming me as able cubic C 1-xAlxN s uc u es [10,11,13]. The C -L2,3 edge spec a,
ep esen ed in Fig 5 ( igh ), only di e in he ela i e in ensi y o he L2 and L3 esonances.
The alues o he L3/L2 a ios (Δy) ha e been measu ed and he ob ained alues a e included
o hei compa ison. The a e age alues a e ound a ound 1.25 close o a C N, con i ming
he iden i ica ion o he C N as he ch omium ni ide phase o med in he C AlN-based
coa ings. A u he de ailed in es iga ion is cu en ly unde going on his laye ed
mic os uc u e in a FEG STEM mic oscope wi h EELS spec oscopy and HAADF de ec o
wi h bigge la e al esolu ion o comple e he ilm cha ac e iza ion.
7
3.2. The mal and oxida ion esis ance
In o de o s udy he oxida ion esis ance he samples ha e been annealed in ai a 1000ºC
du ing 2h. SEM/EDX c oss-sec ion images o C N, C AlN, C AlZ N and C AlYN ilms a e
his he mal ea men a e shown in Fig. 6. In he C N sample, he oxida ion has des oyed he
o iginal columna mic os uc u e leading o a polyc ys alline mo phology whe e he c ys als
on he su ace g ew la ge . On he con a y, he emaining samples s ill main ain he same
columna mic os uc u e as-deposi ed and a op laye o di e en con as whose hickness
depends on he sample (300 nm, 750 nm and 175 nm o pu e C AlN and Z - and Y-
con aining samples espec i ely). The chemical composi ion o he ou e mos and inne laye s
was analysed by EDX o in es iga e he in luence o he dopan Y o Z in he ilm oxida ion.
I mus be men ioned ha simila analysis ca ied ou in he C N ilm (no shown) iden i ied
only C and O signals, indica ing ully oxida ion. Fig. 7 shows he EDX spec a pe o med in
he op laye s and inne egions oge he wi h an elemen al composi ion p o ile along he
en i e hickness o he coa ings. As expec ed he op laye is o med by ch omium and
aluminium oxides o med by ou wa d and inwa d di usion o hese me als and oxygen
espec i ely. Howe e , i is clea ly in e ed ha oxygen p og essed u he in he C AlZ N
coa ing, o ming a la ge oxides scale. Compa ing he EDX spec a shown in Figs. 7a and 7b,
he ni ogen signal is compa a i ely much lowe in he C AlZ N sample indica ing ha
oxida ion p ocess p og esses o a u he ex en . The in ensi y a io O/N measu ed om he
EDX spec a was ound o be 0.9 (C AlZ N) and 0.4 (C AlYN) in ag eemen wi h p e ious
esul s. A ending o he Z and Y signals i is obse ed a Z deple ion in he oxide laye while
he Y con en emains almos cons an in he inne and ou e pa . The good oxida ion
esis ance was also con i med by examining he coa ings by XRD a e hea ing up o 1000ºC.
Fig. 8 depic s he XRD pa e ns whe e i can be seen he (111), (200) and (220) e lec ions o
C (Al)N phase as p edominan componen besides incipien peaks om C 2O3 phase. No
8
signi ican di e ences in in ensi y a e obse ed depending on he ype o dopan (Z o Y)
al hough i can be no iced ha he C 2O3 c ys alli es a e mo e andomly dis ibu ed in he case
o C AlZ N han in he C AlYN ilm whe e he <120> a 41.6º is he p e e en ial o ien a ion.
Aluminium oxides a e no de ec ed indica ing ha his elemen mus be p esen o ming
mix u es wi h ch omium oxides o in amo phous s a e. This ac migh be an in luence o
y ium elemen on he g ow h mechanism o he oxide scale ha yielded an imp o ed
esis ance agains oxida ion. In summa y, hese esul s demons a e a be e p o ec ion agains
oxida ion o C AlYN coa ing composi ion up o empe a u es o 1000ºC. Y ium a oms
appea o di use ou concomi an ly wi h C and Al o ming a mo e e icien p o ec i e oxide
laye whils Z a oms howe e seems o concen a e in he unal e ed ilm s uc u e.
Wi h he aim o ob aining complemen a y in o ma ion on he chemical and mic os uc u al
changes occu ing du ing hea ing an in si u annealing o he C AlYN sample was ca ied ou
inside he TEM mic oscope. In Fig. 9a he EELS spec a (N-K and O-K edges) measu ed a
di e en empe a u es a e shown. The O-K edge begins o appea a 1100ºC, below his
empe a u e no oxygen signal is clea ly de ec ed. The N-K edge ine s uc u e becomes mo e
de ined wi h he inc ease o he empe a u e, especially abo e 750ºC, indica i e o a be e
c ys allised C AlN phase. The mos signi ican happened a 1100ºC when oxygen en e ed in o
he ilm s uc u e. This change is ela ed o he decomposi ion o he ni ide by N2- emo al
and oxygen inco po a ion as desc ibed in p e ious publica ions [1,14,17]. A ep esen a i e
TEM image aken a 1000ºC, jus be o e he deg ada ion s a -up, (c . Fig. 9b) shows ha
inside he coa ing he mic os uc u e emains almos unal e ed. The laye ed s uc u e is
main ained bu wi h highe deg ee o he c ys allini y inside he C AlN phase as demons a ed
by XRD.
Conclusions
9
The he mal and oxida ion esis ance o C AlN-based coa ings doped wi h Z o Y ( 2
a .%) p epa ed by magne on spu e ing ha e been s udied compa a i ely. The p epa ed
coa ings a e mainly cons i u ed by cubic C (Al)N phase and show a dense columna
mic os uc u e ha esis ed he oxida ion in ai up o 1000ºC al hough ce ain di e ences in
oxida ion a e a e no iced. Thus, he bene icial e ec o aluminium as p o ec i e agen o C N
phases agains oxygen eac i i y is ein o ced in he case o y ium, educing he oxida ion
a e and modi ying he oxide g ow h mechanism. The addi ion o his elemen p omo es he
o ma ion o a dense mixed (C , Al)-oxide op laye ha a oids inwa d di usion o oxygen.
Zi conium a oms did no di use oge he wi h C and Al and he oxida ion p og esses o a
g ea e ex en . The mic os uc u al and chemical ans o ma ions induced du ing he mal
ea men we e ollowed in si u by TEM/EELS analysis con i ming a high s abili y up o
1000ºC whe e he coa ing began o decompose and oxidize.
Acknowledgmen s
The au ho s a e g a e ul o he Spanish Minis y o Science and Inno a ion (p ojec s No.
MAT2007-66881-C02-01, MAT2010-21597-C02-01 and Consolide FUNCOAT CSD2008-
00023), Jun a de Andalucía (TEP217) and I3P p og amme o CSIC o inancial suppo .
4
wi hin he EL/P p og am (Ga an). The mechanical p ope ies we e measu ed wi h a
Fische scope H100 dynamic mic op obe ins umen using a con en ional Vicke s inden e a
loads up o 10 mN. The maximum load was selec ed in such a way ha he maximum
inden a ion dep h did no exceed 10–15% o he coa ing hickness in o de o a oid he
in luence o he subs a e.
3. Resul s and discussion
3.1. Chemical and mic os uc u al cha ac e iza ion
Table 1 summa izes he chemical composi ion ob ained by EPMA and ha dness and
Young’s modulus alues o he coa ings. The ha dness p ope ies a e ound in he ange o
22-33 GPa wi h H/E a ios close o 0.1. The mic oc ys alline s uc u e o he ou samples
unde s udy is shown in he B agg-B en ano XRD scans o Fig. 1. I can be seen ha he C N-
based coa ings exhibi he main peaks co esponding o C N calsbe gi e (JCPDS 01-076-
2494) al hough wi h di e en p e e ed o ien a ion and deg ee o c ys allini y depending on
he sample. The inco po a ion o me als (Al and Y o Z ) in o he C N la ice esul s in
b oade XRD peaks indica ing smalle c ys alline domains and change o ex u e. Thus, he
C AlZ N coa ing is less ex u ed, mo e simila o C N, wi h <111> p e e ed o ien a ion. In
he case o C AlN and C AlYN ilms, he p e e ed o ien a ions a e obse ed o shi o
<220> and <200> espec i ely.
Rep esen a i e c oss-sec ion SEM mic og aphs o he C N, C AlN, C AlZ N and C AlYN
ilms a e shown in Fig. 2. The ilm hickness alues ypically a y in he 2–3 μm ange o he
C AlN-based coa ings and 5.8 μm o C N. The exac alues a e included in he Table 1. A
ypical columna s uc u e is obse ed al hough ce ain di e ences in column wid h and
po osi y can be no iced. A mo e de ailed analysis by X-TEM allowed o de e mine he la e al
size o he columns being es ima ed in 80 nm o he C AlN sample, 60-70 nm o C AlZ N
and 100-110 nm o he C AlYN sample. These wid h alues co ela e wi h he measu ed

5
ha dness in he sense ha smalle columna sizes gene a e mo e compac s uc u es and
acco dingly highe ha dness p ope ies. Fig 3 shows a con en ional b igh ield X-TEM
image co esponding o he sample C AlYN as ep esen a i e example o he de eloped ilm
mic os uc u e. F om his pic u e i is clea ly no iced ha besides o he ypical columna
mic os uc u e along he g owing di ec ion a pe iodic laye ed s uc u e, pa allel o he
subs a e, is obse ed. This laye ed a chi ec u e is o med by indi idual laye s o di e en
hickness (20-30 nm he da ke laye and 4-8 nm he b igh e one). This pe iodic laye ed
s uc u e appea s in he h ee C AlN-based samples and could be ela ed o he con igu a ion
o he subs a es in espec o he magne on sou ces. Simila mul ilaye s uc u es ha e been
obse ed in ilms p epa ed by magne on spu e ing due o he o a ion o he samples
alongside he di e en a ge s [23,24]. The selec ed a ea elec on di ac ion (SAED) pa e n
ob ained o his coa ing is including as inse in Fig. 3. The p esence o di ac ion ings is
indica i e o he polyc ys alline na u e o he sample. The di ac ion ings can be assigned o
he planes (111), (002) and (220) co esponding o he cubic phase o C (Al)N phase.
Mo eo e , i is obse ed a ce ain p e e en ial o ien a ion o he c ys alli es o he (200) and
(111) planes along he g owing di ec ion.
In Fig. 4 a high- esolu ion ansmission elec on mic og aph ob ained om a c oss-sec ion
image o he C AlYN sample is p esen ed. The measu ed d-spacing o he la ice inges is 2.4
Å ha can be assigned o he (111) plane o cubic C (Al)N phase. The dashed and do ed lines
a e plo ed as eye-guide o indica e he sepa a ion be ween he columna and he mul ilaye
s uc u e espec i ely. I is wo h o men ioning he s uc u al c ys alline cohe ency exis ing
be ween he wo laye s wi h di e en con as abo emen ioned. The EELS analysis pe o med
in he TEM p epa a ions o he coa ings is a powe ul ool o de e mine he chemical bonding
s a e in nanos uc u ed and mul iphase sys ems [25]. The O-K, N-K and C -L2,3 spec a ha e
been measu ed o all he C AlN-based samples and compa ed o C N [26], C 2N and c-AlN
[27] e e ences compounds used as inge p in s. The hcp-AlN spec um is no conside ed as
6
he change o c ys al s uc u e o C 1-xAlxN om cubic o hexagonal appea s a x alues o
0.6-0.7 [10,11], much highe han hose shown by he coa ings unde s udy. The ine s uc u e
o he N-K edge is known o be sensi i e o he local a omic en i onmen and consequen ly i
can be used o iden i ica ion o he ch omium ni ides [26]. No O-K edge could be de ec ed
in none o he samples in ag eemen wi h he low alues o oxygen measu ed by EPMA (< 1
a . %). Fig. 5 depic s he no malized N-K and C -L2,3 edges spec a o he all he samples and
hose co esponding o he e e ence compounds. Some di e en ea u es can be highligh ed
by compa ison o he spec a. The N-K edge o ch omium ni ides show wo main ea u es a
abou 400 and 410 eV al hough hey di e in in ensi y. Thus, he second cha ac e is ic
esonance peak is less p onounced o he C 2N in compa ison o he C N. The edge onse o
he cubic o m o AlN appea s a highe ene gies, displaying he mos in ense ene gy-loss
peak a ound 407 eV. The ELNES s uc u e o he N-K edge o he h ee C (Al)N-based
coa ings is simila o he C N e e ence wi h he pa icula i ies o a diminu ion o he in ensi y
o he i s peak and he de ec ion o a small shoulde a 407 eV. These di e ences can be
a ibu ed o he Al inco po a ion in he C N phase and/o he o ma ion o AlN phases in he
coa ings. Ne e heless, acco ding o he low Al con en and p e ious published wo ks he
obse ed changes can be a he associa ed o he inco po a ion o Al inside he cubic C N
la ice o ming me as able cubic C 1-xAlxN s uc u es [10,11,13]. The C -L2,3 edge spec a,
ep esen ed in Fig 5 ( igh ), only di e in he ela i e in ensi y o he L2 and L3 esonances.
The alues o he L3/L2 a ios (Δy) ha e been measu ed and he ob ained alues a e included
o hei compa ison. The a e age alues a e ound a ound 1.25 close o a C N, con i ming
he iden i ica ion o he C N as he ch omium ni ide phase o med in he C AlN-based
coa ings. A u he de ailed in es iga ion is cu en ly unde going on his laye ed
mic os uc u e in a FEG STEM mic oscope wi h EELS spec oscopy and HAADF de ec o
wi h bigge la e al esolu ion o comple e he ilm cha ac e iza ion.
7
3.2. The mal and oxida ion esis ance
In o de o s udy he oxida ion esis ance he samples ha e been annealed in ai a 1000ºC
du ing 2h. SEM/EDX c oss-sec ion images o C N, C AlN, C AlZ N and C AlYN ilms a e
his he mal ea men a e shown in Fig. 6. In he C N sample, he oxida ion has des oyed he
o iginal columna mic os uc u e leading o a polyc ys alline mo phology whe e he c ys als
on he su ace g ew la ge . On he con a y, he emaining samples s ill main ain he same
columna mic os uc u e as-deposi ed and a op laye o di e en con as whose hickness
depends on he sample (300 nm, 750 nm and 175 nm o pu e C AlN and Z - and Y-
con aining samples espec i ely). The chemical composi ion o he ou e mos and inne laye s
was analysed by EDX o in es iga e he in luence o he dopan Y o Z in he ilm oxida ion.
I mus be men ioned ha simila analysis ca ied ou in he C N ilm (no shown) iden i ied
only C and O signals, indica ing ully oxida ion. Fig. 7 shows he EDX spec a pe o med in
he op laye s and inne egions oge he wi h an elemen al composi ion p o ile along he
en i e hickness o he coa ings. As expec ed he op laye is o med by ch omium and
aluminium oxides o med by ou wa d and inwa d di usion o hese me als and oxygen
espec i ely. Howe e , i is clea ly in e ed ha oxygen p og essed u he in he C AlZ N
coa ing, o ming a la ge oxides scale. Compa ing he EDX spec a shown in Figs. 7a and 7b,
he ni ogen signal is compa a i ely much lowe in he C AlZ N sample indica ing ha
oxida ion p ocess p og esses o a u he ex en . The in ensi y a io O/N measu ed om he
EDX spec a was ound o be 0.9 (C AlZ N) and 0.4 (C AlYN) in ag eemen wi h p e ious
esul s. A ending o he Z and Y signals i is obse ed a Z deple ion in he oxide laye while
he Y con en emains almos cons an in he inne and ou e pa . The good oxida ion
esis ance was also con i med by examining he coa ings by XRD a e hea ing up o 1000ºC.
Fig. 8 depic s he XRD pa e ns whe e i can be seen he (111), (200) and (220) e lec ions o
C (Al)N phase as p edominan componen besides incipien peaks om C 2O3 phase. No
8
signi ican di e ences in in ensi y a e obse ed depending on he ype o dopan (Z o Y)
al hough i can be no iced ha he C 2O3 c ys alli es a e mo e andomly dis ibu ed in he case
o C AlZ N han in he C AlYN ilm whe e he <120> a 41.6º is he p e e en ial o ien a ion.
Aluminium oxides a e no de ec ed indica ing ha his elemen mus be p esen o ming
mix u es wi h ch omium oxides o in amo phous s a e. This ac migh be an in luence o
y ium elemen on he g ow h mechanism o he oxide scale ha yielded an imp o ed
esis ance agains oxida ion. In summa y, hese esul s demons a e a be e p o ec ion agains
oxida ion o C AlYN coa ing composi ion up o empe a u es o 1000ºC. Y ium a oms
appea o di use ou concomi an ly wi h C and Al o ming a mo e e icien p o ec i e oxide
laye whils Z a oms howe e seems o concen a e in he unal e ed ilm s uc u e.
Wi h he aim o ob aining complemen a y in o ma ion on he chemical and mic os uc u al
changes occu ing du ing hea ing an in si u annealing o he C AlYN sample was ca ied ou
inside he TEM mic oscope. In Fig. 9a he EELS spec a (N-K and O-K edges) measu ed a
di e en empe a u es a e shown. The O-K edge begins o appea a 1100ºC, below his
empe a u e no oxygen signal is clea ly de ec ed. The N-K edge ine s uc u e becomes mo e
de ined wi h he inc ease o he empe a u e, especially abo e 750ºC, indica i e o a be e
c ys allised C AlN phase. The mos signi ican happened a 1100ºC when oxygen en e ed in o
he ilm s uc u e. This change is ela ed o he decomposi ion o he ni ide by N2- emo al
and oxygen inco po a ion as desc ibed in p e ious publica ions [1,14,17]. A ep esen a i e
TEM image aken a 1000ºC, jus be o e he deg ada ion s a -up, (c . Fig. 9b) shows ha
inside he coa ing he mic os uc u e emains almos unal e ed. The laye ed s uc u e is
main ained bu wi h highe deg ee o he c ys allini y inside he C AlN phase as demons a ed
by XRD.
Conclusions
9
The he mal and oxida ion esis ance o C AlN-based coa ings doped wi h Z o Y ( 2
a .%) p epa ed by magne on spu e ing ha e been s udied compa a i ely. The p epa ed
coa ings a e mainly cons i u ed by cubic C (Al)N phase and show a dense columna
mic os uc u e ha esis ed he oxida ion in ai up o 1000ºC al hough ce ain di e ences in
oxida ion a e a e no iced. Thus, he bene icial e ec o aluminium as p o ec i e agen o C N
phases agains oxygen eac i i y is ein o ced in he case o y ium, educing he oxida ion
a e and modi ying he oxide g ow h mechanism. The addi ion o his elemen p omo es he
o ma ion o a dense mixed (C , Al)-oxide op laye ha a oids inwa d di usion o oxygen.
Zi conium a oms did no di use oge he wi h C and Al and he oxida ion p og esses o a
g ea e ex en . The mic os uc u al and chemical ans o ma ions induced du ing he mal
ea men we e ollowed in si u by TEM/EELS analysis con i ming a high s abili y up o
1000ºC whe e he coa ing began o decompose and oxidize.
Acknowledgmen s
The au ho s a e g a e ul o he Spanish Minis y o Science and Inno a ion (p ojec s No.
MAT2007-66881-C02-01, MAT2010-21597-C02-01 and Consolide FUNCOAT CSD2008-
00023), Jun a de Andalucía (TEP217) and I3P p og amme o CSIC o inancial suppo .

10
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12
Figu e cap ions
1. XRD di ac og ams o he C Al(Y,Z )N coa ings unde s udy. A C N di ac ion
pa e n is included o compa ison pu poses.
2. SEM c oss-sec ional iews o he C N, C AlN, C AlZ N and C AlYN coa ings.
3. X-TEM image ob ained om he C AlYN coa ing. The SAED pa e n is included as
inse .
4. HRTEM image ob ained om a c oss-sec ion p epa a ion o he C AlYN coa ing.
5. N-K and C -L2,3 edges o he EELS spec a o all he C AlN-based samples and hose
co esponding o he e e ence compounds (C N, C 2N and c-AlN).
6. X-SEM images aken a e oxida ion in ai a 1000ºC o he C N, C AlN, C AlZ N
and C AlYN coa ings.
7. EDX analysis ca ied ou in he c oss sec ion p epa a ions o he C AlZ N and
C AlYN samples a e hea ing a 1000`C. Spec a ob ained om he opmos laye
and inne pa o he C AlZ N (le ) and C AlYN ( igh ) coa ings. Elemen al chemical
composi ion p o ile ob ained ac oss he C AlZ N (le ) and C AlYN ( igh ) coa ings.
8. XRD di ac og ams o he C AlZ N and C AlYN coa ings a e oxida ion in ai a
1000º. ( symbols co espond o C N (JCPDS ca d# 01-076-2494) and  symbols
co espond o C 2O3 peaks (JCPDS ca d# 01-076-0147).
9. a) E olu ion o he N-K and O-K edge EELS spec a o he C AlYN sample du ing
annealing in acuum up o 1000ºC and b) TEM pic u e e ealing he mul ilaye ed
s uc u e be o e o al decomposi ion p oduced a 1100ºC.
Table 1. Chemical composi ion, hickness and mechanical p ope ies o he C (Al)N-
based coa ings.
C
Al
Y o Z
N
hickness
H
E
Sample
a .%
(μm)
(GPa)
(GPa)
C N
45.6
-
-
54.4
5.8
27
265
C AlN
36.5
8.3
-
55.2
3.3
30
304
C AlYN
38.6
5.1
1.7
54.6
2.4
22
231
C AlZ N
38.8
4.5
2.0
54.8
2.8
33
317
Table(s)
Figu e(s)
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Figu e 7a
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Figu e 7b
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Figu e 7c
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Figu e 7d
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Figu e 8
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Figu e 9a
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Figu e 9b
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