Improving hardness and toughness of plasma sprayed Ti-Si-C nano-composite coatings by post Ar-annealing

Ti-Si-C (TSC) composite coatings were fabricated by plasma spraying using Ti/Si/graphite agglomerates as feedstock. Ar-annealing was carried out to reduce the intrinsic defects and increase the performance of the as-sprayed TSC coating. The effects of the annealing temperature (500-900 degrees C) on the microstructures and mechanical performances of the TSC coatings were investigated. All TSC coatings consisted of TiC, Ti5Si3 and MAX phase Ti3SiC2. With the increase in temperature (>700 degrees C), TiC became predominant, while the Ti3SiC2 phase content increased, which was accompanied by a decrease in Ti5Si3 content. The high-temperature annealing (>700 degrees C) led to a homogenous microstructure with a relatively low porosity and increased number of micro-cracks. Notably, the hardness and fracture toughness of the TSC coating were simultaneously increased after the annealing, from 1164 HV to 1.96 MPa m(1/2) to 1560 HV and 3.45 MPa m(1/2), respectively. The formation of nanoscale TiC and Ti5Si3 with a network distribution, uniform and dense microstructure, and toughening effects of Ti3SiC2 and micro-cracks provided the high mechanical performances of the TSC composite coatings.

Automated summary

Ti-Si-C composite coatings were fabricated by plasma spraying using Ti/Si/graphite agglomerates as feedstock. Ar-annealing was carried out to enhance the performance of the coatings. The coatings showed improved mechanical properties after annealing, with increased hardness, fracture toughness, and a uniform microstructure.