Examination of the platinum effect on the oxidation behavior of nickel-aluminide coatings

[摘要] Oxidation resistant nickel-aluminide coatings are designed to develop a protective alumina scale during high temperature exposure. It is well established that platinum additions, typically about 6-8 at.%, provide substantial improvements in oxidation resistance of such coatings, yet the nature of 14 the platinum effect is still not fully understood. In this work, the oxidation behavior of two commercial NiAl and NiPtAl coatings deposited on the same Ni-base single crystal alloy CMSX4 was analyzed. Cyclic and isothermal oxidation tests were conducted at 1150 degrees C in air. Microstructure development and alumina/coating interface chemistry were studied as a function of oxidation time. Numerous voids developed at the Al2O3/NiAl interface, and sulfur was found to segregate at the void surfaces and at the contact interface, leading to spallation of the scale over the convex areas along ridges on the coating surface. The presence of platinum prevented sulfur segregation and void formation at the Al2O3/NiPtAl interface. As a result, the Al2O3 scale on the NiPtAl coating remained adherent and virtually no spallation was observed even after prolonged cyclic oxidation. (c) 2007 Elsevier B.V. All rights reserved.

[发布日期] 2007-12-15

[效力级别]  Proceedings Paper

[关键词] NiAl;alumina;NiPtAl;sulfur;segregation;adhesion