Effects Of Post-Annealing On Microstructure And Mechanical Properties Of Plasma Sprayed Ti-Si-C Composite Coatings With Al Addition

In this study, Ti-Si-C composite coatings were fabricated by plasma spraying using Ti/SiC/C/Al powder mixtures, and then these coatings were annealed at 500-900 degrees C in an Ar atmosphere. The influences of post-annealing on the microstructure and mechanical properties were analyzed via X-ray diffraction (XRD), scanning electron microscope (SEM) and micro-hardness tester. Results showed that the annealing treatment hardly changed the phase structure of the composite coatings. Coatings before and after annealing were composed of Ti5Si3, Ti3SiC2 and TiC phases. Compared with coatings without annealing, the peak intensity of Ti3SiC2 increased, the porosities decreased and the microstructure became more uniform after annealing. The composite coatings showed an increased microhardness and fracture toughness, which reached the maximum value of 1232 HV0.2 and 3.19 MPa.m(1/2) when annealed at 700 degrees C. The improvement of mechanical properties was mainly attributed to the more uniform microstructure and the toughening effect of closed micro-cracks.