Plasma-sprayed Ti-Si-C coatings and their crystallization behaviors depending on Ti powder content

Abstract

For plasma sprayed ceramic coatings, their crystallization behaviors are significantly different from conventional crystal solidification due to the rapid solidification rate, which would affect their mechanical properties. At present, there are few studies on the crystallization behaviors of the sprayed ceramic coatings. In this work, the Ti-Si-C ceramic coatings were reactive-plasma-sprayed using Ti/Si/graphite agglomerated powders with different Ti powder contents. Their crystallization behaviors and microhardness were investigated. The results demonstrated that the Ti-Si-C coatings mainly composed of TiC/Ti5Si3/Ti3SiC2 phases. With the increase of Ti contents, the Ti3SiC2 and Ti5Si3 phases decreased first and then increased, while the TiC phases content showed an opposite trend. As the Ti content increased, the columnar crystals were gradually perpendicular to the surface. The inner part of the lamellae composed of equiaxed crystals and columnar crystals, and the crystalline morphology of the coating cross-sections all displayed a lamellar columnar structure. The maximum microhardness of the coatings (HV 1201 ± 100) was obtained at a Ti/Si/graphite ratio of 3:1:2.