Tool life and surface integrity when turning titanium aluminides with PCD tools under conventional wet cutting and cryogenic cooling

The high-performance machining of difficult-to-cut alloys requires the development and optimization of high-performance tools, able to withstand the thermo-mechanical tool load without compromising the surface quality of produced components. In this context, the machinability of titanium aluminides still represents a demanding challenge. In this paper, the performance of cubic boron nitride (CBN) and polycrystalline diamond (PCD) cutting inserts is compared to that of uncoated and coated carbide tools. Longitudinal external turning tests were performed on a Ti-43.5Al-4Nb-1Mo-0.1B (TNM) at.% cast and hot isostatically pressed (HIPed) γ-TiAl alloy, by using a conventional lubrication supply. In addition, PCD tools were also applied under cryogenic cooling with liquid nitrogen. Results proved that PCD cutting tools have the potential to improve the machining productivity of titanium aluminides, due to their high hardness and excellent thermal conductivity. A noteworthy further increase of tool life was possible by using PCD cutting inserts under cryogenic cooling conditions.