Preparation Of MCrAlY Coatings By The Method Of Mechanical Alloying

During the process of mechanical alloying, the powder undergoes cold welding and the resulted refinement. Due to the repeated collisions and cold welding, a fraction of powder tends to adhere to the surface of balls and the inner wall of chamber, so as to form a coating layer. Based on this principle, NiCrAl·Y₂O₃ and NiCrAlCo·Y₂O₃ powder were used to prepare MCrAlY thermal barrier coatings on the inner surface of a tubular component. Then the certain coatings were laser remelted. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) were used to investigate the microstructure and elements distributing. Micro-hardness test, scratch adhesion test and high temperature oxidation experiment were carried out to inspect the properties of coating layer.The NiCrAlY coating was successfully deposited on the steel substrate. The results show that the rotating speed and milling time had important effects on coating layer. The coating with the largest thickness and micro-hardness was obtained by setting a bowl rotation speed of 400r/min and a milling time of 10h.The NiCrAlCoY coating prepared at the same parameters was thicker than the NiCrAlY coating and the properties of this coating were much better.The laser remelting of the coating has resulted in significant dilution of coating due to inter diffusion of atoms. Very dense and homogeneous structures have been obtained by laser remelting of coatings.Based all the results, the author put forwards the formation mechanism of coating layer during ball milling and the high-temperature oxidation mechanism.