Machinability analysis of VAT 32® nickel based superalloy using commercial and experimental milling inserts

• Autor(a) principal: Callisaya, Emanuele Schneider
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://hdl.handle.net/11449/204952
• topic: Machining; Milling; Nickel Superalloy; Alumina-based tool; Coated carbide insert; HSM; Usinagem; Fresamento; Superliga de Níquel; Ligas Resistentes ao Calor; Ferramentas de corte

Over the past decades, the superalloy metallurgy industry has made possible many innovations with high impact to the metal-mechanic industry. However, currently, these industries have to cope with both the technical and commercial challenges of new rigid environmental regulations. In this scenario, due to a more restrict series of environmental requirements, a new nickel intermediate superalloy designated VAT 32® was developed for application in automotive high performance valves. The VAT 32® superalloy presents high wear and high temperatures resistance and lower production costs if compared to traditionally applied superalloys. However, due to its chemical composition and microstructure, serious difficulties are observed in its machining process, making it very difficult to machine and limiting its application. Therefore, in order to study the machinability of the VAT 32® new superalloy considering the milling process, the present research work evaluated the alloy’s machinability by applying experimental alumina-based ceramic cutting tools (Al2O3-MgO) developed by the research group of the Materials and Technology Department of the São Paulo State University (UNESP), in comparison to TiAlN-TiN PVD-coated commercial carbide tools. The machining process output variables analyzed were power consumption, vibration, acoustic emission, resulting surface quality (roughness Ra, Rt and Rz), tools wear, chip formation and the specific cutting pressure (Ksm). To evaluate the main effects in machining it was applied the analysis of variance (ANOVA) and normality tests conducted according the design of experiments of Full-Factorial methodology. The dry finishing machining by milling was executed to the cutting speeds of 60, 80 e 100 m/min for the carbide inserts and to 700, 800 and 900 m/min to the ceramic inserts (HSM). Results obtained reveal that it was possible to accomplish the VAT 32® superalloy machining through milling within standard surface quality ranges, to both cutting tools applied. The aluminabased ceramic inserts allowed satisfactory roughness results (Ra 0.734 µm) associated to similar wear per cutting length results Vb*1000/Lc (0.015) in comparison to the coated carbide inserts. The Al2O3-MgO inserts are recommended for machining the VAT 32® at speeds of 900 m/min and low feed of 0.05 mm/t due to its high chemical stability and hardness, allowing the production of shear type chips. The coated carbide tools presented a superior performance to machine the VAT 32® by milling, being the best roughness (Ra 0.608 µm), flank wear Vb (0.125 mm) and Vb*1000/Lc (0.010) results found to the cutting speed of 60m/min and feed of 0.10mm/t, that generate segmented chips with loose arc form, excellent for good handling and disposal.