Microstructural evolution and oxidation behavior of CSS-42L martensitic stainless bearing steel under high-temperature sliding wear

For CSS-42L, a martensitic bearing steel used in high-temperature environments, elucidating its high-temperature tribological mechanisms is fundamental to ensuring its stable operation. In this study, sliding wear experiments were conducted over the temperature range of 25 °C to 450 °C, revealing the temperature-dependent evolution of wear resistance, microstructural changes, and oxidation behavior. The results indicate that the wear rate increased from 3.02×10 -6 mm 3 N -1 m -1 to 7.24×10 -6 mm 3 N -1 m -1 as the temperature rose from 25 °C to 350 °C, but rose sharply to 23.57×10 -6 mm 3 N -1 m -1 at 450 °C. As the temperature increased, the martensite–austenite phase equilibrium progressively shifted toward austenite. Under contact stress, retained austenite transformed into martensite at 25 °C; no significant transformation occurred at 250 °C; and martensite transformed into austenite at 350 °C. At 450 °C, due to the instability of martensite, increased contact stress, and heat accumulation, martensite decomposed into ferrite and austenite. The oxide layer within the wear track was formed through the accumulation and subsequent slow oxidation of metallic debris. The oxide layer loosely spalled at 25 °C, became dense and prevented direct contact between the silicon carbide balls and the substrate at 250 °C and 350 °C, but cracked and spalled at 450 °C due to a mismatch in plastic deformation, resulting in three-body abrasive wear. The microstructure evolution and wear mechanisms at different temperatures revealed in this study provide significant reference value for the industrial application of CSS-42L steel.