The enhanced cohesive performance of magnetron sputtered Cr coatings on steel substrate via controlling columnar grain structures

This study investigates the effect of columnar grain structure on the cohesion of chromium (Cr) coatings, which is crucial for preventing cracking and enhancing durability. Cr coatings with varying columnar grain structures were prepared by adjusting magnetron sputtering deposition time. The relationship between grain structure, surface roughness, residual stress, and cohesion was examined. XRD results showed that all Cr coatings exhibited preferred orientations along the (211) plane. As deposition time increased, both grain size and coating thickness grew, leading to higher surface roughness and reduced residual stress, which in turn affected coating cohesion. The peak cohesion of 21.8 N was achieved when the grain size reached 690 nm and the coating thickness was 8.5 µm. Excessive residual stress and high surface roughness promoted crack formation, reducing cohesion. This study highlights the importance of controlling coating surface roughness and residual stress to enhance cohesion and provides valuable insights for developing advanced hard coatings.