Refining the mechanistic understanding of microstructural decay during rolling contact fatigue in 52100 bearing steel tempered at high temperature

Abstract

Subsurface rolling contact fatigue (RCF) failure occurs beneath heavily loaded hard contacts like gears, bearings, and cams. This study investigates microstructural decay beneath a RCF-tested surface in AISI/SAE 52100 bearing steel tempered at 240 ℃. RCF tests were conducted at 100 ℃ with a maximum Hertzian contact pressure of 4 GPa for four stress cycles. Microstructural characterization utilized scanning electron microscopy, electron backscatter diffraction, transmission Kikuchi diffraction, and transmission electron microscopy. Due to high tempering temperature, white etching bands (WEBs) were observed without preceding dark etching regions. The microstructural decay sequence involved: (1) formation of elongated ferrite and ferrite microbands, (2) complete dissolution of tempered carbides and partial dissolution of residual cementite, (3) formation of WEBs composed of nano-sized ferrite grains (100–300 nm) transformed from ferrite microbands, and (4) appearance of lenticular carbides. Within the WEBs, most nano-sized grains had high-angle grain boundaries, while the fraction of low-angle grain boundaries increased in later stages of RCF. Lenticular carbides formed alongside elongated ferrite and coalesced nano-sized ferritic grains.

Effect of Carbides on Thermos-Plastic and Crack Initiation and Expansion of High-Carbon Chromium-Bearing Steel Castings

“…High-carbon chromium-bearing steel is characterized by high hardness, high fatigue performance, and high wear resistance and is widely used in emerging industries such as precision equipment [1], wind power generation [2], high-speed railways [3], and aerospace applications [4]. The high hardness and wear resistance of bearing steel can be achieved by solid solution strengthening of carbon and precipitation strengthening of carbide [5], and excellent wear resistance can be achieved by adding chromium and microalloying elements [6].…”