Formation mechanisms of white layers induced by hard turning of AISI 52100 steel

White layer formation mechanism in dry turning hardened steel

“…Chou and Evans (1999)used the Al2O3-TiC ceramic tool to cut hardened AISI52100 steel, the result shows the volume fraction of austenite in the white layer is more than that in the substrate, so they consider that large amount of cutting heat generated in cutting process causes surface temperature up to austenite phase transformation temperature, then the machined surface is rapidly cooled after contacting with air and undergoes martensite transformation. Another viewpoint is that the plastic deformation is a main factor in formation process of white layer (Hosseini et al, 2015;Ranganath et al, 2009;Zhang et al, 1997). Rice et al(1991) observed the white layer through transmission electron microscopy(TEM),the result shows that the dislocations with high density exist in the machined surface.…”

Microstructural evolution associated with shear location of AISI 52100 under high strain rate loading

“…Dislocation cell blocks dominated the microstructure and then subgrains began to emerge in copper which was severely deformed at liquid nitrogen temperature [42]. The grain refinement of AISI 52100 [31] has the same way that elongated martensite laths produced by hard turning were partitioned into rectangular-shaped sub-grains. The grain refinement in AISI 4340, AISI 304L and α-titanium led the authors in [23] to suggest that microstructure evolution within shear bands is a shear deformation-dominant process and does not significantly depend on crystal structures.…”

“…Many studies on shear localization relate the initial temperature rise directly to ASBs formation mechanism [8,19,25,26,31,39]. A typical example is given by Xue and Gray [25] who conducted a detailed calculation of temperature rise at various stages of shear band formation in 316L by using the dynamic stress-strain data.…”

“…Inside of the white layers, nana-sized grains and substructures were observed, which has been proved to be the result of dynamic recovery/dynamic recrystallization [31,36,37]. Hosseini [31] attributed the mechanically and thermally white layers produced in hard turning of AISI 52100 as deformed and transformed bands. But a detailed investigation of high strain rate shear localization in AISI 52100 has not yet been reported so far.…”

“…Mostly, these materials have good ductility. High strength and low ductility bearing steels exhibit white layers or white bands in high-speed cutting [31,32] and rolling contact fatigue [33][34][35]. Inside of the white layers, nana-sized grains and substructures were observed, which has been proved to be the result of dynamic recovery/dynamic recrystallization [31,36,37].…”