Heat Treating 400-Series Stainless In Air Without Flaking

During heat treating in air, 400-series stainless steels suffer from significant oxidation. It will be shown that doping the surface with a small amount of reactive element effect (REE) material can minimize this oxidation. Examples of REE materials include aluminum, silicon and cerium. After this treatment, the thermal oxides that form are thin and protective rather than thick and flaking. The net result of the very thin thermal oxide is significantly reduced secondary operations. The process can be done in the field without any hazardous materials or special equipment. Complex geometries can be protected. As an example of the effectiveness of the treatment, the thermal oxide on untreated 410 stainless steel was 450µm while on the treated surface it was less than 1µm. The reduction of heat treat warp has also been demonstrated. Additionally, the method can be used to improve the life of heat treat furnace components.