Nano-reinforcing Composite Coatings Fabricated by Laser Internal Nitridation

Abstract

The internal nitridation composite coatings with in-suit synthesis nano particulates were fabricated by laser cladding on titanium alloy substrate for investigating the formation mechanisms and performances. The microstructures, phase composition and mechanical property were studied by SEM, XRD, micro-hardness tests and cavitation erosion tests. The results show that, Ti2N reinforcing particulates are in the size of ∼50 nm and disperse homogeneously in the α-Ti matrix. As a result, the average hardness of the laser internal nitridation coating is 371.4 HV which is about 23.8% higher than that of the substrate. The analysis indicates that, the difficulty of long range diffusion of atoms and the in-suit precipitation from the parent grains in solid state are the reason why Ti2N are only of ∼50 nm diameters. For 6h cavitation erosion tests, the cumulative volume loss of internal nitridation sample is only ∼62.7% of the substrate, which shows well prospect for application.