EFFECT OF STAND-OFF DISTANCE ON THE MICROSTRUCTURAL AND MECHANICAL PROPERTIES OF AlZn PSEUDO-ALLOY COATING PREPARED VIA WIRE ARC SPRAY PROCESS
Metallization or protective coating layer consists of aluminium, zinc, and their alloys have been one of the most effective corrosion mitigation methods, therefore are utilized to protect steel. Among various coating techniques, Twin Wire Arc Spray (TWAS) process has been widely adopted for decades in surface engineering to protect components due to its cost efficiency, flexibility, and it promotes superior coating quality. However, it is crucial to set the right parameters as coating properties via TWAS usually have high roughness and low adhesion to substrates. In this study, two different wires feedstock of Al and Zn were employed to produce pseudo-alloy of Al-50Zn coating on mild steel substrates while stand-off distance (SOD) coating parameter was varied at 100, 150, 200, 250, and 300 mm respectively. The effect on the properties of developed coating layer on microstructure, thickness, hardness, roughness, and adhesion were carried out. The microstructure, structural, and morphological analyses were conducted using SEM, XRD, and metallographic microscope. Results have shown that the samples prepared at 100 mm have demonstrated the best coating quality compared to others and there are pronounced correlations between process parameters and all coating properties. The average thickness of coating at 100 mm SOD was recorded to be the lowest at 230 μm with the highest hardness and adhesion values, 109Hv and 8.3MPa respectively and lowest surface roughness of 5.1 microns. This is in contrast to coating prepared at 300 mm SOD that have demonstrated poor qualities both microstructural and mechanical properties.