HVOF bi-layer coating with controlled porosity for use in thermal barrier coatings

摘要

A bi-layer bond coating for use on metal alloy components exposed to hostile thermal and chemical environment, such as a gas turbine engine used to generate electricity and the method for applying such coatings. The preferred coatings include a bi-layer bond coat (10) applied to the metal substrate (18), with both layers being applied using high velocity oxy-fuel (hvof) thermal spraying. In one embodiment, bond coatings in accordance with the invention can be used in combination with a thermal barrier coating (12) ("tbc"). However, the invention can also take other forms, such as a stand alone overlay coating. Bi-layer bond coatings in accordance with the invention consist of a dense first inner layer (16) (such as iron, nickel or cobalt-based alloys) that provides oxidation protection to the metal substrate, and a second outer layer (14) having controlled porosity that tends to promote roughness, mechanical compliance, and promotes adherence of the tbc. Preferably, the outer, less dense layer of the bi-layer bond coat is formed from a mixture of metallic powder and polyester to adjust and control the porosity, but without sacrificing mechanical compliance. Together, the layers enhance adherence to the substrate and improve the overall life of the coating system.