Study On Laser Cladding Oxidation Resistance Coatings And Its Properties

A Laser cladding deposition technique was performed to make (NiCoCrAlY)coating. This coat is expected to work as a High-temperature resist for TiAlintermetallic substrate. Metallographic analysis, microhardness, SEM, XRD wereused to find the appropriate Laser cladding parameters (power and scan velocity),the deposit morphology and the oxidation behavior of the coat. Study showed that a mixture of Pyroxylin and alloy powder and acetone,which was deposited on the substrate, can help to form a high performancecoating. About Laser cladding parameters, 900W in power and 350mm/min invelocity are relatively good. After 100 hours oxidation experiment at 1000℃,a mixed TiO2,Al2O3layer was formed at the top of (NiCoCrAlY) coating and (NiCoCrAlY+5%Al2O3)coating. However the layer on top of (NiCoCrAlY+20%Al) coating was mainlyAl2O3. The results of high temperature oxidation tests in air at 1000℃showed thatthe oxidation resistance of the laser cladding (NiCoCrAlY+20%Al) wassignificantly higher than that of (NiCoCrAlY+5%Al2O3) and (NiCoCrAlY)coatings. Analysis tells that to add Aluminum in the powder can help to form ahigh quality coating. The mechanisms of Al to improve oxidation resistance wereDiscussed. Al can fine the grain size of cladding coatings and hinder thediffusion of other ions. It can also increase the content of Al3+ in the coating.Which all ensure to form a high density Al2O3 layer on the substrate and topromote its oxidation resistance.