Effect of soft substrate on the indentation damage in silicon carbide deposited on graphite

Indentation-induced damage is investigated in silicon carbide (SiC) deposit ed on graphite substrate. The SiC films have been grown by LPCVD (Low Press ure Chemical Vapor Deposition) method using MTS (CH3SiCl3) as a source gas and H-2 as a diluent gas to provide highly dense deposited layer and strong interfacial bonding. The elastic-plastic mismatch is very high to induce d istinctive damages in the coating and the substrate layer. The specimens wi th various coating thicknesses are prepared by changing CVD condition or me chanical polishing. Indentation damages with different sizes are introduced by controlling indentation load in Nanoindentation, Vickers indentation an d Hertzian indentation test. Basic mechanical properties such as hardness, toughness, elastic modulus are evaluated against coating thickness. Mechani cal properties are sensitive to the indentation load and coating thickness. The results indicate that coating thickness has a vital importance on the design of hard coating/soft substrate system because the soft substrate aff ects on the mechanical properties. (C) 2000 Kluwer Academic Publishers.