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

This study reports on the effects of surface modification by laser texturing on tribological performances of nitride steel for automotive engine applications. In particular, a comparison of tribological properties on untextured and textured 30NiCrMo12 nitride steel was made among hydrodynamic, mixed and boundary lubrication regimes.Ordered arrays of circular dimples were created on nitride 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 normal applied loads ranging from 1 to 10 N. Static counterpart was a custom pin of 100Cr6 steel. Two different configurations were studied: “single drop” and “dry contact”. Long sliding condition tests and Stribeck curves were obtained. Finally, Secondary Electron Microscopy imaging, Energy Dispersive Spectroscopy and Auger Electron 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 condition at high normal applied load and for long sliding time.