Effects of Spraying Process Parameters on Porosity and Microhardness of Arc-sprayed Ni-Al Coating

The Ni-Al coating was sprayed by using an electric arc spray equipment with Ni-Al alloy wires. The porosity variations of Ni-Al coating were examined in a well-designed orthogonal test to attain an optimized spraying process. The intensity and velocity of the flame flow and particle temperature were detected by an online detection system. Morphologies and compositions of the Ni-Al coating were analyzed using a scanning electron microscope, and the microhardness was measured to optimize spraying parameters are as follows: electrical arc current of 130 A, voltage of 33 V and atomizing air pressure of 0.4 MPa, spraying distance of 120 mm.The results show that the spraying voltage, spraying current, atomizing air pressure and spray distance can induce different influence on the porosity of the Ni-Al coating. Under optimized spraying parameters, the minimum porosity of the Ni-Al coating can decrease to 5.5%and the coating shows the typical layer structure.