Martensitic transformation cracking in high carbon steels for bearings

Abstract

Cracking generates usually due to the internal stress during martensitic transformation in high carbon steels, for instance the ‘1C–1.5Cr’ bearing steels. A novel low-density ‘1.2C–1.5Cr–5Al’ alloy has been designed recently for bearing application in previous research. The effect of morphology of martensite plates on the transformation cracking has been proposed and investigated in comparison between the ‘1.2C–1.5Cr–5Al’ and ‘1C–1.5Cr’ steels in this research. Based on the mechanisms proposed, the tendency for transformation cracking in the novel alloy with more carbon addition has been discussed compared with the ‘1C–1.5Cr’ steel. This paper is part of a Themed Issue on Recent developments in bearing steels.

Enhancing the Robustness and Efficiency in the Production of Medium Mn Steels by Al Addition

“…The intercritical annealing temperature and durations were designed based on the capabilities of an industrial continuous annealing line which has a higher-precision temperature control than batch annealing lines. The selective etching of the prior austenite grain boundary was performed using the saturated picric acid solution (Kaisa Chemical, Tianjin, China) with wetting agents (Jahwa, Shanghai, China) [29,30]. The prior austenite grain size was observed by standard optical microscopy (OM, Olympus BX53M, Tokyo, Japan) and measured using the mean linear intercept method [29].…”

“…The selective etching of the prior austenite grain boundary was performed using the saturated picric acid solution (Kaisa Chemical, Tianjin, China) with wetting agents (Jahwa, Shanghai, China) [29,30]. The prior austenite grain size was observed by standard optical microscopy (OM, Olympus BX53M, Tokyo, Japan) and measured using the mean linear intercept method [29]. The microstructure of the annealed specimens was observed in field emission transmission electron microscopy (TEM, Tecnai G2 F20, FEI, Hillsboro, OR, USA) combined with energy-dispersive spectroscopy (EDS, EDAX, Mahwah, NJ, USA) with an operating voltage of 200 kV.…”

A novel approach for modeling retained austenite transformations during rolling contact fatigue

“…To incorporate the effect of habit planes, crystal orientations are randomly assigned to each element within the model. For SAE 52100, the habit planes are approximated as [2, 2, 5] using miller indices . Shear and normal stresses are then resolved along habit planes based on the assigned crystal orientation.…”

“…For SAE 52100, the habit planes are approximated as [2,2,5] using miller indices. 44 Shear and normal stresses are then resolved along habit planes based on the assigned crystal orientation. These resolved stresses then directly modify the driving force required for RA to transform.…”

Recent developments in bearing steels

“…The austenite grain size also matters because coarser plates fracture more easily. 33 Bai et al 34 show that in a high aluminium bearing steel, even adding 1.2 wt-% carbon does not result in a greater tendency for cracking when compared with 52100 steel, primarily because the austenite grain size is fine.…”