Surface texture and heat treatment on the friction performance of cam tappet experimental and fluid-solid coupling numerical study

In order to improve tribological properties of tappets made of GCr15 bearing steel, a combination of martensitic heat treatment and surface texture was applied to the GCr15 bearing steel. The texture was designed based on a fluid-solid coupling simulation performed using COMSOl, and effectiveness of the designed texture was verified by performed wear tests using a pin-disk line contact rotary motion tester under oil lubrication condition. The worn surface morphology and wear mechanism for the friction pair were analyzed with three-dimensional scanning microscopy and scanning electron microscopy to reveal the antifriction behavior and wear resistance. Results of the study show that the heat treatment increased the surface hardness and significantly reduced wear of the GCr15 bearing steel. The designed surface texture helped reduce the contact area, store tiny wear debris, and increase the oil film pressure, thus improving the tribological performance. However, the texture edge was prone to severe plastic deformation due to the stress concentration and lowered lattice confinement. The martensitic heat treatment involving tempering effectively reduced plastic flow at the edge of texture. The combination of texture and the martensitic heat treatment considerably improved the tribological properties of GCr15 steel.