Effect of sputtering times on the properties of NiCr-Al

The objective of the present work was to investigate the mechanical properties of NiCr-Al coating deposited by plasma sputtering technique. NiCr was firstly deposited on a carbon steel surface using sputtering times of 60, 90, 120, 180 and 240 minutes, whereas Al was subsequently deposited using a time of 30 minutes for all specimens. The results showed that the structure of the surface observed by SEM indicates a good density. The structure formation of NiCr-Al was clarified by XRD. The hardness test of the product surface conducted by a Vickers indentation tester indicates that the average hardness of uncoated steel substrate was 172.512 HV. The hardness of NiCr surface was 191.256 HV. Further layer addition using Al on NiCr indicates that the hardness of NiCr-Al surface sputtered by NiCr for 60, 120, 180 and 240 minutes, followed by Al for 30 minutes, were 279.912, 253.056, 231.264 and 213.888 HV, respectively. The reduced hardness of NiCr-Al with the increased sputtering time was attributed to the higher diffusion of Al into NiCr.