Effect of Cu content on hardness and wear properties in (Cr, Mo, Cu)N film

Effects of Cu addition on hardness and wear properties of (Cr, Mo) N films were investigated by nanoindentation and ball-on-disk measurements. (Cr_100-x-yMo_xCu_y)N films were deposited onto a stainless steel substrate by a reactive DC magnetron sputtering of Cr₅₀Mo₅₀ and Cu targets under the mixture of argon (45 ccm) and nitrogen (5 ccm) gases. The hardness of the film increased from 21.9 to 23.5 GPa by Cu addition of y = 3.4 of Cu addition and then drastically decreased with further increasing Cu addition. The drastic decrease in hardness is caused by the formation of amorphous structure. In crystalline films, it was found that the change of hardness obeys the inverse Hall-Petch relationship. The wear mechanism of the film was changed by increasing Cu addition, adhesive wear (y = 0), lubricated wear (3.4 ≤ y ≤ 12.6) and abrasive wear (y ≥ 20.4). It was also found from wear track observation that the lubricated wear in the Cu content region of 3.4 ≤ y ≤ 12.6 was obtained by the formation of the oxide debris resulted from the film with as small amount of Cu (3.4 ≤ y ≤ 12.6). With further increase in Cu content (y≥ 20.4), the film was severely worn because of its low hardness of the amorphous film.