Sliding Friction and Wear Properties of 40CrNiMo Steel after Laser Hardening against GCr15 Steel under Oil Lubrication

40CrNiMo steel, which is a commonly used material for sprag clutch wedges, is widely used in practice, and the surface wear will seriously affect the performance of the product. In this study, the surface of 40CrNiMo steel was strengthened at two scanning speeds by laser hardening. After laser hardening, the surface hardness can reach the use requirement of the clutch wedge. By changing the speed and temperature, the friction and wear testing machine was used to study the wear behavior of 40CrNiMo steel after laser hardening against GCr15 steel under oil lubrication, the friction coefficient, wear amount and wear morphology under different conditions were analyzed. The results show that, at the normal temperature, with the increase in the sliding speed, the friction coefficient showed a gradually decreasing trend, the width of the wear surface of the steel increased, and the wear amount increased. The increase in temperature led to an increase in the friction coefficient and the fluctuation, wear width and wear amount of the hardened layer. At the temperature of 20 °C, abrasive wear was the main form of wear, and the furrow formed special channels for the lubricating oil to help reduce the friction coefficient under oil lubrication. At high temperatures, the depth of the furrow further increased, and the degree of adhesive wear and oxidative wear gradually increased. The research provides a reference for the application of material in the sprag clutch.