HIGH TEMPERATURE MECHANICAL PROPERTIES OF CVD-SiC THIN FILMS

Abstract

Silicon carbide (SiC) coatings were fabricated using a chemical vapor deposition (CVD) process on to a graphite substrate at different deposition temperatures. The mechanical properties such as hardness, modulus, and creep properties from room temperature to 500 degrees C were investigated using nanoindentation techniques. The SiC coatings deposited at 1300 degrees C exhibited a small grain size (0:2 similar to 0.4 mu m) and [111] preferred orientation, while the coatings obtained at 1350 degrees C had a large grain size (0.5 similar to 1.0 mu m) and [220] preferred orientation. The hardness was decreased with testing temperature, but no significant change in the modulus was measured with testing temperature from high temperature nanoindentation test, and the apparent creep behavior was observed in the high temperature. The high temperature mechanical properties of CVD-SiC coati ngs were relate to their microstructure and crystal orientation, and CVD-SiC coatings deposited at 1300 degrees C exhibited high stability and reliability at high temperature