Patent ID: 7553517
Filing Date: 2009-06-30
Classification: C23C

Abstract:
1. A method of diffusing cerium into chromia oxide forming substrates in a non-oxidizing environment to form a protective chromia scale comprising: (a) preparing a cerium oxide paste, the cerium oxide paste comprised of cerium oxide and a halide activator, balance inert filler and inert transport fluid, wherein the cerium oxide is at least 10 wt % of the combined weight of the cerium oxide, halide activator, and inert filler, and wherein the halide activator is at least about 0.1 wt % of the combined weight of the cerium oxide and the halide activator; (b) applying the cerium oxide paste over a surface of an alloy substrate comprised of at least 4 wt % chromium, forming a paste covered alloy substrate; (c) heating the paste covered alloy substrate at a temperature of about 400° C. to about 1300° C. in a non-oxidizing atmosphere, for a period of time sufficient to diffuse cerium into the surface of the alloy substrate and produce a CeCrO (d) removing any remaining cerium oxide paste from the surface of the alloy substrate.