Study on mechanism of improving wear and corrosion properties of 20CrMnTi ring gear surface by laser carburizing

Abstract

Laser carburizing is an effective method to improve the surface properties of materials. In order to improve the corrosion resistance and wear resistance of 20CrMnTi ring gear surface, firstly, the material surface was carburized by laser. Secondly, the hardness, wear resistance and corrosion resistance of the surface before and after carburization were tested. Finally, the electronic structure of 20CrMnTi before and after carburization was calculated based on the first principle method of density functional theory. The results show that the surface microstructure after laser carburizing is mainly high carbon martensite and cementite, and the hardness is increased by 109.5%. There are adhesive wear and abrasive wear before and after carburizing. Interstitial carbon increases the density of dislocation and lattice distortion, and significantly improves the wear resistance of the surface. At the same time, the addition of interstitial carbon reduces the corrosion current density, increases the self-corrosion potential, and improves the corrosion resistance of the material. The first principle calculation results show that the interstitial carbon increases the strength of covalent bond and ionic bond, which is the main reason for the improvement of hardness and wear resistance, and the interstitial carbon reduces the density of states at Fermi level and inhibits electron transfer, which is the essential reason for improving corrosion resistance.