Multilayer thin film CrN coating on aerospace AL7075-T6 alloy for surface integrity enhancement

Chromium nitride (CrN) coating has emerged as a new alternative in machining applications. CrN has good thermal stability, low deposition temperature, and excellent wear and corrosion resistance. However, no precise information exists yet regarding the ideal coating parameter conditions that lead to higher surface integrity. For this reason, an optimization study is desired - a study on the parameters of CrN coating on aerospace Al7075-T6 alloy using physical vapor deposition magnetron sputtering. The present research work investigates the effects of temperature as well as nitrogen flow rate and DC power on coated samples' surface hardness, adhesion, surface roughness, and microstructure. To carry out the investigation, the Taguchi optimization method with L₁₆ (3⁴) orthogonal array was applied. However, to obtain optimum parameters for superior surface integrity, signal/noise (S/N) response analysis method was employed. Finally, confirmation tests with the best parameter combinations attained in the optimization process were carried out to demonstrate the progress made. Ultimately, surface hardness of coated Al7075-T6 was enhanced by 15.33 %, adhesion by 24.3 %, and surface roughness by 7.22 %.