Study on the Anti-Friction Mechanism of Nitriding Surface Texture 304 Steel

In order to improve the extensive application of 304 steel in various industrial fields, dimples with different diameter and spacing arrayed on the surface of 304 steel were prepared by laser etching. Then the nitriding treatment was applied on the textured surface and 304 steel matrix surface. The surface microhardness, surface work function, apparent contact angle of the surface before and after nitriding, and surface morphology of the compound modification surface were tested. The tribological properties of five different samples were tested by a rotating friction and wear tester under oil lubrication conditions. The finite element simulation analysis is carried out with a single micro dimple and the upper specimen as the simulation object. The results show that the surface hardness of the compound modification surface is much higher than that of the 304 steel matrix. The surface work function and apparent contact angle of the nitrided surface is larger than that of the 304 steel matrix. These factors lead to the difficulty of abrasive particle stripping, which enhances anti-wear performance of nitrided smooth surface under the lubrication condition. The micro dimple will lead to the change of liquid streamlining, promote the change of liquid pressure in different regions, and result in convergence and divergence regions. But the dynamic pressure of the oil in the micro texture did not play an obvious role in reducing friction at a lower speed. The anti-friction and anti-wear properties of the compound modified surface are better than those of the nitrided smooth surface, which mainly is attributed to lubricant storage in texture and reduction of the real contact area.