Toward hard yet tough CrAlSiN coatings via compositional grading

A set of CrAlSiN coatings was synthesized in homogenous and graded composition via magnetron sputtering in mixed Ar and N2 ambient. The microstructures are investigated using glancing angle X-ray diffractometry, field emission scanning electron microscopy and transmission electron microscopy. With compositional grading, CrAlSiN coatings exhibit much improved scratch adhesion strength and better crack propagation resistance at a little expense of hardness.

► CrAlSiN coatings with gradient Si addition (from 0 to 8.5 at.%) are synthesized and characterized.
► Compositional gradient coating was dominant in columnar structure with refined CrAlN nanograins at the top.
► Improved scratch toughness and adhesion force were found in the gradient coatings as compared to the homogeneous coatings.