PREPARATION AND HARDNESS OF A FUNCTIONALLY GRADED Ni-Al COATING

Abstract

A functionally graded Ni-Al coating can improve the hardness of low-carbon steel, which can then adapt to various conditions due to a high hardness. The primary purpose of this research was the preparation of a Ni-Al coating by adopting a two-step method including nickel plating and pack aluminizing. The coating phase and morphology were characterized with XRD, SEM and EDS. Subsequently, the hardness of the Ni-Al coating was measured using a nanoindentation test. The results show that different aluminum contents in the coating surface lead to different coating phases, mainly Ni2Al3. The change in the coating phases conformed to the Ni-Al binary phase diagram. The Ni-Al coating showed a continuous gradient structure and composition. In addition, the coating also showed continuous gradient variation, relating to the hardness.