Preparation of β-SiC Coatings Using 1,2-Dimethyldisilane as Precursor

A cold-wall upstream reactor was designed to study the deposition of P-Sic layers on WC-Co hard metal substrates. Experiments demonstrated that P-Sic coatings can be easily deposited on inductively heated substrates at temperatures between 1000-1400°C by thermal decomposition of 1,2-dimethyldisilane under normal pressure conditions. It was shown that this silicon compound is an advanced precursor for the preparation of P-Sic coatings. The reaction temperature influenced the S ic growth rate as well as the microstructure of the coating. Different reaction mechanisms occurred at these temperatures. Fine grained cauliflower-like coatings were obtained below 1100°C while monolithically crystallised coatings were formed above 1200°C. These morphological differences are associated with the coating growth rates, which reached a maximum at 1100°C and decreased rapidly at higher temperatures. The precursor concentration in the reaction gas had to be kept relatively low in order to obtain homogeneous, crystalline Sic coatings and to prevent "smoking", i.e. nucleation of fine particles in the gas phase.