Revealing the Evolution in Microstructure and Mechanical Properties of Cam Tappet After Surface Texture Combination Nitriding Treatment Under Different Process Sequences

Severe wear of the tappet surface in the engine cam‐tappet friction pair under heavy load and high‐speed conditions reduces the vehicle's service life and accelerates the emission of pollutant gases. In this study, laser surface texturing and ion nitriding are employed to modify the surface of GCr15 steel through a double treatment process. The effect of the process sequence is rarely discussed in previous research and thus particularly focuses on the changes in tappet properties resulting from different process sequences. The results reveal that the wear resistance of the tappet improves to varying extents after surface modification. It is also observed that the friction coefficient of the tappet is highly sensitive to the sequence of processes. This is attributed to the fact that nitriding improves the hardness of the microconvex structures formed during the texturing, which leads to higher contact stresses during friction, thereby compromising the integrity of the textured. Additionally, nitriding enhances the tappet's corrosion resistance. Therefore, considering the sequence of processes in the Combined modification of GCr15 steel of the tappet, it provides valuable data for the design and optimization of tappets.