Abstract: A method of providing a protective, corrosion-resistant thin coating of a MCrX alloy on a carbon or low-alloy steel pipe or tube where M is one of nickel, cobalt or iron or combination thereof and X is one of molybdenum, silicon, tungsten or combination thereof, and heat treating the coating to metallurgically bond the coating onto a steel substrate of the pipe or tube. The coating may be deposited in one or two layers by plasma transferred arc deposition or may be deposited as a slurry coating or thermal spray coating with sintering of the coating. The steel substrate is prepared for coating by at least one of boring, honing, bright finishing, grit blasting, grinding, chemical pickling or electro-polishing of the substrate.

Abstract: A method for protecting high temperature stainless steel from coking and corrosion at elevated temperatures in corrosive environments, such as during ethylene production, by coating the stainless steel with an overlay coating of MCrAlX in which M is nickel, cobalt, iron or a mixture thereof and X is yttrium, hafnium, zirconium, lanthanum or combination thereof. The overlay coating and stainless steel substrate are heat-treated to metallurgically bond the overlay coating to the substrate and to form a multiphased microstructure. The overlay coating preferably is aluminized by depositing a layer of aluminum thereon and subjecting the resulting coating to oxidation to form an alumina surface layer. An intermediary aluminum-containing diffusion coating may be deposited directly onto the stainless steel substrate prior to deposition of the overlay coating to form a protective interlayer between the stainless steel substrate and overlay coating.

Abstract: There is provided a surface alloyed component which comprises a base alloy with a diffusion barrier layer enriched in silicon and chromium being provided adjacent thereto. An enrichment pool layer is created adjacent the diffusion barrier and contains silicon and chromium and optionally titanium or aluminum. The method comprises depositing a surface alloy on the base alloy at a temperature in the range of 400 to 1000° C. and heat treating the surface alloy at a ramp temperature rate of at least 5C°/minute, preferably 10 to 20° C./minute, to a desired maximum temperature at which the surface alloyed component is maintained for a time sufficient to provide the enrichment pool or the enrichment pool with a diffusion barrier layer. A reactive gas treatment may be used to generate a replenishable protective oxide scale of alumina or chromia on the outermost surface of the surface alloyed component.

Abstract: A method for protecting high temperature stainless steel from coking and corrosion at elevated temperatures in corrosive environments, such as during ethylene production by pyrolysis of hydrocarbons or the reduction of oxide ores, by coating the stainless steel with a coating of MCrAlX in which M is nickel, cobalt, iron or a mixture thereof and X is yttrium, hafnium, zirconium, lanthanum or combination thereof deposited onto and metallurgically bonded to the stainless steel by plasma transferred arc deposition of atomized powder of MCrAlX. The coating has a thick, dense, continuous and smooth transition region providing an effective metallurgically bond of the coating with the stainless steel. The coating retains a relatively high aluminum content which permits generation of an adherent alumina layer on the surface, providing good resistance to high temperature oxidation together with good anti-coking and hot erosion resistance properties.

Abstract: There is provided a surface alloyed component which comprises a base alloy with a diffusion barrier layer enriched in silicon and chromium being provided adjacent thereto. An enrichment pool layer is created adjacent said diffusion barrier and contains silicon and chromium and optionally titanium or aluminum. A reactive gas treatment may be used to generate a replenishable protective scale on the outermost surface of said component.