MEASUREMENT OF ADHESION PROPERTIES OF Ni2Al3 COATING WITH A MICRO SCRATCH TESTER AND AUTOMATIC SCRATCH TESTER

A functionally graded Ni2Al3 coating, prepared with a two-step method of nickel electroplating and pack aluminizing, can improve the hardness of low-carbon steel and other surface performance features. However, the adhesion between the coating and the substrate is an important factor affecting these properties. The primary purpose of this study was to introduce a test for determining the adhesion of the Ni2Al3 coating, which included two tools, namely a micro scratch tester (MST) and a WS-2000 automatic scratch tester, used for measuring the coating adhesion and observing the scratch morphology. Results show that the adhesion is about 14 N according to the MST, which is equivalent to 56 N obtained with WS-2000. As the load increases, the scratches gradually become larger and deeper. Finally, the surface morphology shows cracks, indicating that the coating has failed.