Effect of Ni content on CrNiN coatings prepared by RF magnetron sputtering

• RF sputtered CrNiN coatings with different Ni content are prepared.
• All coatings form a nearly feature-less surface morphology with 10–20 nm grains.
• A transition from a coarse to fine columnar structure due to Ni is determined.
• 2.92 at.% Ni increases hardness mainly due to the blocking of grain boundary sliding.
• 8.79 at.% Ni leads to decreased hardness as a result of too much soft metal.

CrNiN coatings with various Ni content were deposited by RF reactive magnetron sputtering from Cr–Ni alloy targets. The influence of Ni content on phase structure, preferred orientation, microstructure and hardness of the coatings was investigated. The results show that RF sputtered CrNiN coatings are mainly composed of CrN phase, present columnar growth, and have a nearly feature-less surface morphology. The preferred orientation changes from CrN(220) to CrN(111) as Ni content is increased from 2.92 to 8.79 at.%. The doped Ni can favor dense structure and improve coating surface smoothness, but cannot refine grains. The coating hardness is increased by adding 2.92 at.% Ni due to the effect of discontinuous Ni coverage on hindering grain boundary sliding, dense structure and smoother surface. As Ni content is increased to 8.79 at.%, the hardness is then decreased as a result of too much soft metal and larger grain size.