Thermo-mechanical coupling mechanisms for white layer formation on machined surface of powder metallurgical nickel-based superalloy

Abstract

Through investigations of high-speed milling experiments of PM nickel-based superalloy FGH95, the influence of the cutting speed on white layer formation is investigated. 2D finite element simulation of high-speed milling process is carried out. The distribution of temperature field, strain field and strain-rate field at different cutting speeds are obtained. Research results show that the white layer thickness increases with the cutting speed. However, the thickness of white layer decreases while the cutting speed increases a step further. The combined influences of temperature, strain and strain-rate at machined subsurface layer results to the onsets of phase transformation and grain refinement, which in turn promote the formation of white layer. Severe plastic deformation decreases the critical temperature for white layer formation, while high strain-rate increases the critical temperature of white layer formation.