A comparative study of nanolaminate CrN/Mo2N and CrN/W2N as hard and corrosion resistant coatings

Nanolaminate coatings (NLC) consisting of alternated CrN coupled with either cubic tungsten nitride (beta-W2N) or molybdenum nitride (gamma-Mo2N) were deposited on cold worked tool steel substrates using reactive DC reactive magnetron sputtering for improved mechanical and corrosion resistance. The CrN/gamma-Mo2N and CrN/beta-W2N nanolaminate systems were found to perform better than the corresponding single-layer systems, with both mechanical and electrochemical properties improving by decreasing the individual layer thickness from 100 to 5 nm. The CrN/beta-W2N NLC combined the high hardness value of W2N with the low corrosion current of CrN. The CrN/gamma-Mo2N NLC showed synergistic improvements consisting of both higher hardness and lower corrosion currents with respect to the constituent materials alone. The dependence of mechanical and corrosion properties on the bilayer period is discussed in terms of the grain size, residual stresses and texture of the constituent materials and the nanostructured character of the multilayer architecture.