Chromizing process

Claim 1

A method according to claim 1 wherein the protective atmosphere is essentially a hydrogen atmosphere.

Claim 13

A method of forming a stainless steel coating on steel sheet which inhibits sticking between adjacent sheet faces when heat treated in a pack of sheets, which method comprises a. applying to at least one surface of each of a series of sheets a film of a volatile adhesive liquid substance, b. applying to the filmed surface of said sheets a uniform distribution of a powder comprised of a mixture of an iron and chromium metal powder containing not less than 20 percent by weight of chromium and a halide of the group consisting of the alkali metals and alkaline earth metals in an amount between about 5 percent and 20 percent of the total metal powder commingled and blended throughout with said iron and chromium powder to form a homogenous mixture, c. compacting the said powder on said sheet by applying pressure thereto, d. placing the sheets in a pack with adjacent faces in substantial contact through intervening layers of said compacted powder, e. heating the compacted powder coated pack of sheets in a protective atmosphere for a time and at a temperature sufficient to cause diffusion between the sheets and the powder to thereby form an adherent stainless steel coating on said sheets without adhesion between said faces and opposite stainless steel coatings, and f. opening said pack without damage to the coating to reveal a smooth undamaged coating on said sheets.

Claim 22

A method of preventing sticking between adjacent thin leaves of ferrous base metal in a chromizing operation wherein i. a thin film of a volatile adhesive liquid substance is applied to the surface of said leaves of base metal, ii. a powder comprised of a mixture of an iron and chromium metal powder containing not less than 20 percent by weight of chromium is applied to the surface of the leaves and compacted thereon by applied external pressure, iii. the leaves of base metal are placed in a package with adjacent faces in contact through intervening layers of compacted powder, and iv. the package of leaves of base metal is heated in a protective atmosphere for a time and at a temperature sufficient to cause diffusion between the leaves of base metal and the chromium containing powder to form an adheRent stainless steel coating upon the surfaces of the base metal leaves, comprising: a. thoroughly mixing a halide from the group consisting of the alkali metals and alkaline earth metals with the iron and chromium powder in step (ii) in an amount between 5 percent and 20 percent of the total metal powder to form a homogenous mixture prior to compacting the powder upon the surface of the base metal, and b. separating the leaves of base metal after the heating and diffusion step of (iv) without damage to the coating to reveal a smooth undamaged stainless coating on the face of the base metal leaves.