Spray shadowing for stress relief and mechanical locking in thick protective coatings

Abstract

An article with a surface that includes undercut grooves depending beneath the surface to a bottom portion, where the grooves have an upper width on the surface and a lower width on the bottom portion connected by side walls, and where at least one of said side walls connects the upper width to the lower width to form an undercut angle with the surface of less than 90°. The article is covered with a coating that contains weak paths for stress relief. The coating fills the undercut grooves and ranges above the surface with a thickness from about 0.1 to 50 mm.

Description

STATEMENT REGARDING FEDERAL RIGHTS [0001] This invention was made with government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy. The government has certain rights in the invention.FIELD OF THE INVENTION [0002] The present invention relates generally to protective coating systems, and, more particularly to the stress relief and mechanical locking of a thick thermal sprayed coating. BACKGROUND OF THE INVENTION [0003] Protective coatings are generally used to protect the underlying material, the substrate, from damage due to direct exposure to outside environments. Historical protective coatings were detrimentally affected by differential dilation, i.e., a difference in expansion / contraction of two (or more) objects, so that dimensions that aligned at one time do not align at another time. This can be the result of mechanical loads, temperature gradients, or different coefficients of thermal expansion. Any or all of these causes might apply for coati...

AI Technical Summary

Benefits of technology

[0009] In accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention includes an article with a surface that includes undercut grooves depending beneath the surface to a bottom portion, where the grooves have an upper width on the surface and a lower width on the bottom portion

Problems solved by technology

Historical protective coatings were detrimentally affected by differential dilation, i.e., a difference in expansion / contraction of two (or more) objects, so that dimensions that aligned at one time do not align at another time.

Induced stresses can cause the loss of bonding between the coating and the underlying material.

When coatings are subjected to repeated heating and cooling cycles, thermally induced stresses and strains accumulate within the coating.

Where thick coatings, {fraction (1 / 16)} of an inch (1.6 mm) or greater, were applied to flat surfaces, problems of coating shrinkage and lifting at the edges were significant.

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