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.

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In this study, synchronous cutting of concave and convex surfaces for hypoid gear was achieved using a duplex helical method. Precise, nonlinear optimization of the transmission error driven by machine tool parameters was performed to reduce the vibration noise of the gear pair. First, the transmission error curve and contact path of the tooth surface of the initial pinion were solved using tooth contact analysis. Second, according to the preset parabolic transmission error curve, the initial gear was used to generate the target pinion, which coincided with the contact path of the initial pinion. Finally, a deviation correction model of the discrete points, corresponding to the contact paths on the concave and convex surfaces of the target and initial pinions, was established. This model was solved using the Levenberg–Marquard algorithm with the trust region strategy, to obtain optimized machine tool parameters. Synchronous optimization of the transmission errors of concave and convex surfaces of the pinion was achieved by correcting the deviations of the contact points. The effectiveness of the proposed method was verified by a numerical example and by performing a contact area rolling test.