Metal components with silicon-containing protective coatings substantially free of chromium and methods of forming such protective coatings
Metal components with a protective coating containing silicon and a process for forming such protective coatings. The protective coating is formed by applying a silicon-containing fluid composition to the metal component as a silicon-containing layer and then heating the silicon-containing layer to a temperature exceeding 400° F.
1. A coating process for protecting a surface of a substantially chromium-free metal component, the coating process comprising:
combining a liquid and a dopant that is dissolvable in the liquid to form a substantially chromium-free, silicon-containing liquid composition;
applying a layer of the substantially chromium-free, silicon-containing liquid composition to the surface of the substantially chromium-free metal component;
after the layer is applied, placing the substantially chromium-free metal component in a non-oxidizing atmosphere; and
after the metal component is placed in the non-oxidizing atmosphere, heating the layer to a temperature greater than 400° F. to form a substantially chromium-free, silicon-containing protective coating on the surface that includes silicon from the silicon-containing liquid composition and a metal from the substantially chromium-free metal component.
2. The coating process of claim 1 further comprising:
after the layer is applied and before the substantially chromium-free metal component is placed in the non-oxidizing atmosphere, curing the substantially chromium-free, silicon-containing liquid composition at a temperature less than 400° F.
3. The coating process of claim 1 wherein the dopant is selected from the group consisting of yttrium, hafnium, and combinations thereof.
4. The coating process of claim 1 wherein the substantially chromium-free metal component is composed of iron, aluminum, titanium, copper, nickel, or an alloy of two or more of these metals.
5. The coating process of claim 1 wherein placing the substantially chromium-free metal component in the non-oxidizing atmosphere comprises:
evacuating atmospheric gases from a heating chamber holding the substantially chromium-free metal component; and
after the atmospheric gases are evacuated, filling the heating chamber with an inert gas.
6. The coating process of claim 1 wherein the liquid is a silane.
7. The coating process of claim 1 wherein the liquid is a silicon-containing liquid.