The effect of QPQ treatment on the wear and corrosion resistance of 42CrMo bearing steel

This study investigates the impact of QPQ (Quench–Polish–Quench) treatment parameters—580 °C and 620 °C, with holding times of 90 min and 120 min—on the microstructure, wear resistance, and corrosion resistance of 42CrMo bearing steel. Microstructural evolution was analyzed by OM, SEM, and XRD, while hardness, friction-wear, and electrochemical tests assessed performance. QPQ treatment produced a three-layer surface structure comprising an oxide film, a compound layer rich in Fe₂₋₃N and Cr₂N, and a diffusion layer. At 620 °C for 120 min, the compound layer reached a thickness of 24.01 μm, with a diffusion depth of 377 μm, and the surface hardness increased to 710.9 HV 0.2 . The lowest friction coefficient (0.33) and wear loss were observed for the 620 °C × 90 min sample, whereas the highest corrosion resistance occurred for the 580 °C × 120 min sample (E corr = − 0.476 V, log 10 (I corr ) = − 6.242, R p = 2643 Ω). Temperature exerted a more substantial influence on layer growth and nitrogen diffusion than holding time. However, prolonged treatment at 620 °C resulted in spallation, embrittlement, and porosity, thereby degrading the wear and corrosion performance.