Remanufacture of hot forging tools and dies using laser metal deposition with powder and a hard-facing alloy Stellite 21®

Foster, Jim et al. Article Remanufacture of hot forging tools and dies using laser metal deposition with powder and a hard-facing alloy Stellite 21® Journal of Remanufacturing Provided in Cooperation with: Springer Nature Suggested Citation: Foster, Jim et al. (2019) : Remanufacture of hot forging tools and dies using laser metal deposition with powder and a hard-facing alloy Stellite 21®, Journal of Remanufacturing, ISSN 2210-4690, Springer, Heidelberg, Vol. 9, Iss. 3, pp. 189-203, https://doi.org/10.1007/s13243-018-0063-9 This Version is available at: https://hdl.handle.net/10419/232983 Standard-Nutzungsbedingungen: Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden. Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen. 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If the documents have been made available under an Open Content Licence (especially Creative Commons Licences), you may exercise further usage rights as specified in the indicated licence. https://creativecommons.org/licenses/by/4.0/ RESEARCH Remanufacture of hot forging tools and dies using laser metal deposition with powder and a hard-facing alloy Stellite 21® Jim Foster 1 &Crawford Cullen 1 &Stephen Fitzpatrick 1 &Grant Payne 1 &Liza Hall 1 & James Marashi 1 Received: 8 November 2017 /Accepted: 15 October 2018 /Published online: 16 November 2018 #The Author(s) 2018, corrected publication 2019 Abstract Additive Layer Manufacturing (ALM) processes are attracting interest in the forging industry due to their potential suitability for remanufacturing and repair of tools and dies. The ALM process known as Laser Metal Deposition with powder (LMD-p)can be used to provide a hard-facing alloy repair to hot forging tools. This is particularly important on complex tool geometries due their superior wear resistance. The Advanced Forming Research Centre (AFRC) has established a low cost standard test method to evaluate abrasive and adhesive wear on hot forging H13 tool steel dies on an industrial scale 160 kJ Schuler screw press. The bespoke tool design allows researchers to benchmark new and novel coatings, lubricants and additive layers against a known standard. Furthermore, AFRC metrology standard methods ensure repeatability and reproducibility of benchmark results. To evaluate the performance of LMD-pfor remanufacturing of hot forging tools and dies, a cobalt based alloy (Stellite 21®) was selected. Stellite 21®is widely used as a hard-facing alloy as it provides excellent machinability coupled with superior wear characteristics. AFRC standard dies were coated with LMD-pStellite 21®.TheLMD-pcoating was then machined to final geometry and then subjected to hot forging under AFRC standard conditions to compare to benchmark wear characteristics. Adhesive and abrasive wear was evaluated. It was shown that the Stellite 21®LMD-padditive layer performed better in both adhesive and abrasive conditions than standard H13 tools steel dies. Keywords Remanufacture .Additive layer.Laser metal deposition.Forging .Stellite 21®.H13 . Tooling .Dies Journal of Remanufacturing (2019) 9:189–203 https://doi.org/10.1007/s13243-018-0063-9 *Jim Foster [email protected] Extended author information available on the last page of the article Introduction Due to the high costs associated with die replacement and repair, there is a large emphasis across the tool and die sectors (forging, forming, stamping and composite processes) to develop new methods which reduce cost, improve die life, material utilisation and functional performance. Large die sets for super plastic forming fan blades, forging crankshafts and turbine disks can cost ~ £250,000 and have a significant economic impact on the overall component piece part cost. On average this is approximately 10% of turnover [1]. The European tool and die market is estimated at $11 billion USD per year involving >7000 companies [2]. The UK spends around £130 million manufacturing closed die forging tools and sheet metal dies alone. However, these industries are largely SMEs (90%) [2] for whom adopting new methods require significant investment. H13 tool steel is a hot work tool steel that has been the industry standard alloy for forging die applications for a number of years. It has excellent resistance to thermal shock, thermal fatigue, abrasion resistance, and heat resistance [3,4]. H13 tool steel provides the necessary requirements to withstand harsh operating environments. Current die remanufacturing practice is to manually inspect for wear and cracking, then flood weld the entire cavity and machine to the desired geometry. There is limited geometric or dimensional verification of cavity features using this method. Dies can also be completely re-machined to remove wear/cracking and recreate their original geometry. Impacts of the current practice include large costs associated with tool steel volumes; weld alloy materials to fill complete cavity and excessive machine cycle times and consumable costs. Additionally, there are significant lead time challenges due to the complex sequence of multi stage unconnected processes involved. The Additive Layer Manufacturing (ALM) process Laser Metal Deposition (LMD) offers an alternative remanufacturing method for tools and dies. LMD repairs can reduce cost, improve material utilisation and improve functional performance. LMD is an innovative technology that offers significant potential over traditional welding techniques as detailed features can be deposited in specific areas with lower dilution [5]. Furthermore, finer microstructures can be obtained due to fast cooling rates [6] and reduced distortion conditions can be achieved due to lower heat input [7]. Stellite®cobalt based alloys are commonly used in Laser Metal Deposition operations, and in particular, for remanufacturing of components [8,5,9] such as crankshafts [6], shafts [10]and turbine blades [11]. Stellite®alloys exhibit hard facing properties, providing excellent mechanical wear resistance, especially at high temperatures. In addition, they have excellent corrosion, erosion, abrasion, and galling resistance [12]. They also provide good sliding wear resistance [14], which is critical for forging and forming applications. Stellite®alloys and the properties that they exhibit, present significant remanufacturing opportunities to enhance standard H13 tool steel dies. In order to determine the applicability and functional performance of hard facing Stellite® alloys in forging applications, a practical investigation was undertaken to benchmark standard H13 tool steel dies against a H13 tool steel substrate with an LMD Stellite additive layer. Aims of research The aim of this work was to determine whether the remanufacture of hot forging dies is a feasible and viable option for the forging industry and if so, whether LMD-p provided a suitable repair method. Selected powder based materials were considered as candidates for repair and the relative pros and cons considered. Furthermore, by carrying out forging experiments on an industrial scale screw press and assessing the performance of the repaired dies, confidence in LMD-p repairs 190 Journal of Remanufacturing (2019) 9:189–203 would be enhanced from the perspective of the end user. Finally, due to the selective and precise nature of LMD-p deposition, areas of excessive wear could be targeted to enhance the overall die performance. Criteria for die repair The following criteria were considered with respect to LMD-p as a hot forging die repair methodology. a. Ease of repair LMD-p is an ideal candidate for repair of hot forging dies. Laser Metal Deposition equipment and metal powders are readily available and are compatible with selective repair of dies which are exhibiting localised wear. Fig. 1 LMD-pre-manufacturing process Table 1 Material Selection decision matrix Materials Suitability for forging conditions Suitability for remanufacture Suitability for machining Suitability for LMD-p Stellite 6 ✔✔✔✔ Stellite 21 ✔✔✔✔ Stainless steel 316 X NA NA NA Steel alloy 4340 X NA NA NA M2 Tool steel ✔✔✔X COLMONOY®635 X NA NA NA Cr3C2–20(Ni 20Cr) X NA NA NA Inconel®Alloy 718 ✔✔✔✔ Journal of Remanufacturing (2019) 9:189–203 191 b. Machinability It is important to ensure that die repair materials can be machined to final geometry with conventional CNC machines and tooling. c. Wear resistance Remanufacturing processes need to return a worn die set to at least the performance levels of the original die set. LMD-p offers the opportunity to select more robust repair materials to, at a minimum, achieve original performance characteristics or indeed exceed wear resistance properties of the original die set. Furthermore, because LMD-p can be deposited in precisely selected areas, there is an opportunity to improve die performance on hitherto areas prone to excessive wear. d. Hot forging performance The in-service performance of remanufactured hot forging dies must, at a minimum, match the original in terms of output and failure modes. LMD-p repaired dies will be assessed by means of the Advanced Forming Research Centre (AFRC) low cost standard test method to benchmark the hot forging performance of die repairs. Table 2 Stellite 21®chemical composition Co Cr Mo C Ni Other elements present Base 26–29 4.5–6.0 0.20–0.35 2.0–3.0 Fe, Si, Mn Fig. 2 H13 tool steel die insert with ALM 192 Journal of Remanufacturing (2019) 9:189–203 Methods Experimental overview To investigate the feasibility of using LMD-pStellite 21®as a repair material for tools and dies, a suitable rigorous test of the material was required. AFRC research in the field of forging tool die life provided a unique opportunity to investigate forging die repairs on large industrial scale equipment. Furthermore, re-manufacture utilising AFRC CNC machining capabilities also provided insight into the machinability of the selected repair material. The availability of ‘benchmark’wear data allowed direct comparison of the repair material performance in a real life situation. Figure 1illustrates the re-manufacturing process and subsequent evaluation steps. Fig. 3 LMD-pProcess Table 3 LMD-pprocess parameters Parameter Value Unit Substrate material H13 Tool Steel 4Cr5MoSiV1 Deposited material Stellite 21 CH4CoCrFeMnMoNiSiW Powder feed rate 8.2% g/min Laser power (PreHeat) 750 W Laser power (Deposition) 500 W Radius of defocused laser beam on the substrate (PreHeat) 8–10 mm Radius of focused laser beam on the substrate (Deposition) 1.0 mm Ambient temp 298 K Melting temp of substrate 1733 K Melting temp of powder 1568 K Process speed (PreHeat) 10 mm/s Process speed (Deposition) 12 mm/s Laser stand off 12 mm Carrier gas Argon N/A Shield gas Argon N/A Step over 0.5 mm Distance between Nozzle & Substrate 12 mm Journal of Remanufacturing (2019) 9:189–203 193 Repair material selection Several candidate materials are available for repairing tools and dies using LMD-padditive layer manufacturing. Table 1illustrates the decision matrix used to select a suitable material for repair of hot forging dies by LMD-p. The material selected must also retain adequate machining and forging compatibility for re-manufacturing processes after repair. Stellite 21®was selected as a candidate material as it provided the following characteristics: &wear resistance - hard facing alloy &high temperature strength &resistance to thermal and mechanical shock &resistance to galling &metal-to metal sliding wear resistance &good machining characteristics The chemical composition (wt.%) of the cobalt based alloy is shown in Table 2. Fig. 4 Typical LMD-pdeposit Fig. 5 HSC75 CNC Machining centre and machined die insert 194 Journal of Remanufacturing (2019) 9:189–203 Die insert selection Tools and dies can be very expensive to produce and their complex geometry can make evaluation of repairs difficult. However, AFRC has developed a hot-forging standard test method which is low cost to perform and provides benchmark data to allow direct comparison of ALM materials. Figure 2illustrates the AFRC standard low cost die insert and Stellite 21® ALM material is shown in red. The die insert is mirrored around its centre to maximise material utilisation providing two forging trials per die insert. Cylindrical billets are forged on the peak of the die insert (see section 6 for more detail). The die insert is manufactured from H13 tool steel at Rockwell hardness (HRC) 52–54 and is 100 mm × 45 mm × 60 mm in dimension with 2 mm radius peak. Powder laser metal deposition (LMD-p)repair LMD-pis an additive layer manufacturing (ALM) technique wherein a metal powder is conveyed through a nozzle onto a metal substrate. A laser is used to melt a layer of powder into the desired shape along CNC toolpaths (Fig. 3). The process is repeated layer by layer to create a solid three dimensional geometry on the substrate. The laser power required to produce the desired melt pool is in the range 0.5 kW ~ 2.0 kW which, on solidification, results in a fine grain microstructure due to high cooling rate (105 Ks−1). LMD-pproduces a metallurgical ‘fusion’bond with the substrate of density > 99.5 and typical layer thickness of 0.2 mm to 2.5 mm. Distortion is minimised due to the small Heat Affected Zone (HAZ) of the laser with <5% dilution of the substrate. LMD-pwas subcontracted to LAS Ltd., Doncaster, England with the requirement to deposit a minimum of 5 mm Stellite 21®onto the H13 tool steel substrate. Table 3details LMD-pprocess parameters. Figure 4shows a typical AFRC die insert repaired with 5 mm LMD-pdeposited Stellite 21®. Machining of repaired die insert LMD-prepaired die inserts were machined to obtain the original die insert geometry on a DMG Mori HSC75 CNC machining centre as shown in Fig. 5. Table 4 Machining conditions for H13 tool steel and Stellite 21® Coolant Machining strategy Surface speed (mm/min) Feed per tooth H13 Tool Steel Off Roughing 250 0.05 H13 Tool Steel Off Finishing 300 0.05 Stellite 21®On Roughing 30 0.05 Stellite 21®On Finishing 50 0.05 Table 5 H13 tool steel chemical composition CSiMnCrMoV Typical (%) 0.39 1.03 0.45 5.30 1.28 0.95 Journal of Remanufacturing (2019) 9:189–203 195 When compared to H13 tool steel, modified machining parameters were required for Stellite 21®and are detailed in Table 4. Hot forging standard test method The Advanced Forming Research Centre (AFRC) has established a low cost standard test method to evaluate abrasive and adhesive wear [13] on H13 tool steel dies for hot forging applications. H13 tool steel [16] is a chromium-molybdenum-vanadium alloyed steel used in the manufacture of hot forging tools and dies (Table 5). H13 tool steel provides durability, strength, corrosion resistance and high-temperature stability in service. The bespoke tool design allows researchers to benchmark new and novel coatings, lubricants and additive layers against a known data standard and allows researchers to assess the performance of the new processes and materials in terms of abrasive and adhesive wear. The fillet radius (2 mm) has been carefully selected to ensure Die Insert Die Assembly Billet H13 Tool Steel •HRC 52-54 •Fillet/notch geometry •Impart shear stress •Low cost Cylindrical billets •Aluminium – so, no wear •316 stainless steel – low wear •321 stainless steel – low wear •Inconel 718 – high wear Fig. 6 AFRC die set 196 Journal of Remanufacturing (2019) 9:189–203 6. Piasecki A et al (2013) Laser cladding of Stellite 6 on low carbon steel for repairing components in automotive applications using disk laser. Archives of Mechanical Technology and Automation 33(2):25–34 7. 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Available from: https://www.kennametal. com/content/dam/kennametal/kennametal/common/Resources/Catalogs-Literature/Industry%20 Solutions/B-16-05107_KMT_Stellite_HardfacingAlloys_Brochure_EN_LR.pdf [12] 13. Marashi J, Yakushina E, Xirouchakis P, Zante R, Foster J (2017) An evaluation of H13 tool steel deformation in hot forging conditions. J Mater Process Technol 246:276–284 14. Marashi, J., et al. Defining a method of evaluating die life performance by using finite element models (FEM) and a practical open die hot forging method.InAIP Conference Proceedings. 2016. AIP Publishing 15. Uddenholm. H13datasheet. Available from: http://www.bucorp.com/media/H13_data_sheet_09032013.pdf 16. Solutions, D.W. Stellite 21 alloy. Available from: https://static1.squarespace.com/static/56e079802fe131546 a70830d/t/588a1e7f197aea571f37a590/1485446785712/Deloro+MDS+Stellite21+rev00.pdf Publisher’snote Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Affiliations Jim Foster 1 &Crawford Cullen 1 &Stephen Fitzpatrick 1 &Grant Payne 1 &Liza Hall 1 & James Marashi 1 Crawford Cullen [email protected] Stephen Fitzpatrick [email protected] Grant Payne [email protected] Liza Hall [email protected] James Marashi [email protected] 1 Advanced Forming Research Centre, University of Strathclyde, 85 Inchinnan Drive, Glasgow, UK Journal of Remanufacturing (2019) 9:189–203 203