OXIDATION RESISTANCE AND MICROSTRUCTURE OF NI-CR-AL-Y-SI COATING ON NI3AL BASED ALLOY

Oxidation resistance and microstructure of Ni-Cr-Al-Y-Si coating depos ited by vacuum are deposition technique on the unidirectionally solidi fied Ni3Al Alloy IC6, whose typical application is in the manufacture of turbine blades and vanes of jet engines, were studied. The results of the tests show that the room temperature tensile strength and stres s rupture properties at 1100 degrees C of the alloy were not influence d by the coating, and the oxidation resistance of the alloy significan tly improved. In the annealed state, limited interdiffusion of various elements was observed. After cyclic oxidation at 1100 degrees C for 5 00 cycles or stress rupture at 1100 degrees C/90 MPa for 252 h, local composition of both the coating and the base material was observed to vary continuously from the surface to the substrate due to the interdi ffusion of elements between the coating and the substrate and due to t he surface oxidation. The results also suggest that the Ni-Cr-Al-Y-Si coating is beneficial in improving the oxidation resistance of turbine blades and vanes made of Alloy IC6 for application in advanced jet ae ro-engines. (C) 1997 Elsevier Science S.A.