COMPARISON OF 2 MODELS OF THIN DIAMOND FILM MICROHARDNESS DATA TO PREDICT THE HARDNESS OF CVD DIAMOND

Microhardness Knoop indentation testing of diamond films (1-3 mum thic k) on silicon and on a titanium alloy is reported. The measured hardne ss results were influenced by the substrate, and the results were mode lled to give the hardness of the diamond film. Two models were used. T he first was an empirical equation determined from finite element simu lations of the load-displacement response of a hard film on a soft sub strate. The second assumed the measured hardness to be dependent on th e volume of the film and the volume of the substrate deformed. The fir st model gave a better fit in both cases, predicting a diamond film ha rdness of 112 GPa and 59 GPa for the silicon and titanium alloy substr ates respectively. There is a large titanium carbide interfacial layer between the diamond film and the titanium alloy substrate, which is p robably the major reason for the lower predicted hardness result.