Effect of annealing temperature on microstructure and mechanical properties of plasma sprayed TiC-Ti5Si3-Ti3SiC2 composite coatings

Abstract

In this study, Ti-Si-C based composite coatings were fabricated by plasma spraying of aggregated powders of Ti/SiC/graphite. These coatings were subsequently annealed in an Ar atmosphere at 500–1000 °C to study the evolution of the microstructure and properties of the composite coatings. The coatings were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), and micro-hardness tests. The results revealed that the composite coatings before and after annealing were mainly comprised of Ti 3 SiC 2 , Ti 5 Si 3 and TiC phases. The annealing treatment had no significant effect on the phase types but contributed to the formation of more uniform microstructures with reduced porosities and increased micro-cracks. The annealed coatings exhibited an improved microhardness and fracture toughness as the temperature increased, and the highest values recorded were of 1419 HV and 3.00 MPa·m 1/2 , respectively. Compared with the limited reaction time during the spraying process, the post-annealing treatment extended the reaction time, and the reaction proceeded further. The more uniform microstructure, the increase of Ti 3 SiC 2 content and the micro-crack toughening effect contributed to improving the mechanical properties of composite coatings. • Post-annealing treatment was conducted on the plasma sprayed TiC-Ti 5 Si 3 -Ti 3 SiC 2 composite coatings. • The as-annealed composite coatings achieved more uniform microstructure with reduced porosities. • The as-annealed composite coatings showed increased microhardness and fracture toughness with increasing temperature.