Effects of Mo2C, Ni binder and laser surface modification on WC inserts for turning Ti-6Al-4V

Abstract

The effects of rapid pulse electric current sintering (PECS), Ni as a Co binder substitute, Mo2C additions and laser surface modification (LSM) on the microstructure, mechanical properties and machining performance during roughing and finishing turning of Ti-6Al-4 V were investigated. Additions of Mo2C reduced the carbide grain size from 0.65 ± 0.01 μm to 0.5 ± 0.01 μm in liquid phase sintered (LPS) WC-Co/Ni cermets, with the PECS manufactured WC-0.5Cr3C2–3.5Mo2C-10Co (wt%) having the highest hardness. The LSM technique produced a ~2.5 μm self-carbide coating, increasing the surface hardness of all the samples. LSM was done to improve abrasion, attrition and thermal wear resistance. Turning was done at cuttings speeds (vc) of 45–120 m/min, depths of cut (ap) of 0.25–2.0 mm and feeds of 0.15–0.2 mm/revolution, under lubricated conditions. The developed inserts were compared to TH10 (an industrial reference), and performance was assessed by cutting forces, tool wear and tool life. The liquid phase sintered WC-0.5Cr3C2-10Co (wt%) and WC-0.5Cr3C2–3.5Mo2C-10Co (wt%) inserts had longer tool lives than TH10 during roughing at a cutting speed (vc) of 45 m/min, depth of cut (ap) of 2 mm and feed of 0.2 mm/revolution, although TH10 had the best tool life during finishing (vc = 120 m/min, ap = 0.25 mm and feed =0.15 mm/revolution). Generally, LSM had a negligible effect on tool life, WC-Ni based inserts had the shortest tool lives and LPS inserts performed better than PECS inserts.