Effects of nitrogen flow on R.F. reactive magnetron sputtered silicon nitride films on high speed steel

Silicon nitride films were deposited on high speed steel by r.f. reactive magnetron sputtering. The effects of nitrogen flow rate on the deposition rate, chemical composition, microstructure and mechanical properties were evaluated. The deposition rate, nitrogen content, hardness and reduced elastic modulus decreased with increasing nitrogen flow rate. The decrease of coating hardness could decrease constraint stress, and hence decrease the shear stress at the interface, which resulted in higher critical load.