Tribological effects of surface texturing on nitriding steel for high-performance engine applications

Abstract

This study reports on the effects of surface modification by laser texturing on tribological performances of nitriding steel for high-performance engine applications. In particular, a comparison of tribological properties on untextured and textured 30NiCrMo12 nitriding steel was made among hydrodynamic, mixed and boundary lubrication regimes. Ordered arrays of circular dimples were created on nitriding steel surfaces by Laser Surface Texturing. Friction experiments were performed using a pin-on-disc apparatus at sliding speeds ranging from 1 to 12 cm s −1 and nominal contact pressures ranging from 1 to 10 MPa. Static counterpart was a custom pin of 100Cr6 steel. Two different configurations were studied: “single drop” lubrication and “dry contact”. Long sliding condition tests and Stribeck curves were obtained. Finally, Secondary Electron Microscopy imaging and Energy Dispersive Spectroscopy investigations were carried out to study morphology and chemistry at surfaces, before and after tribological tests. Maximum effects of Laser Surface Texturing on friction coefficient and wear have been observed in “single drop” configuration at high normal applied load and for long sliding time.