The ultimate vacuum pressure and the characteristics of sputtered coatings

In this research work, results are presented in relation to the hardness and scratch-test adhesion of W-M-N (M=Ni and Ti) coatings obtained by d.c. reactive sputtering after the deposition chamber has been evacuated to different ultimate vacuum pressures (UVP). Far the range of the ultimate vacuum pressures values used in industrial production (10(-2) to 10(-4) Pa), a variation of this parameter can give rise to important changes in sputtered coatings. Both the hardness and scratch-test values, evaluated for the coatings, increase with decreasing UVP. By analysing the influence of coating roughness on the mechanical properties of the coatings, it is possible to show that this increase is related to their increasing roughness, which can in turn be related to decreasing UVP. Although the cleaning procedure before deposition is similar for all coatings, lower UVP values lead to a more efficient substrate etching by ion bombardment and a higher final coating roughness is obtained.