Process of improving corrosion resistance in porous stainless steel bodies and article

Claim 2

A foraminous body having improved corrosion resistance to aqueous nitric acid, 10%, and being formed of tin-containing water atomized, compacted and sintered austenitic stainless steel alloy powder compacted and sintered to less than 80% of theoretical density and characterized by being formed of a prealloyed stainless steel alloy powder containing from 0.1% to 10% by weight of tin.

Claim 3

A foraminous body as defined in claim 1 wherein the stainless steel powder also contains copper.

Claim 4

A foraminous body as defined in claim 2 wherein the stainless steel powder contains about 1% tin and 2% copper.

Claim 5

A process for improving the corrosion resistance to aqueous nitric acid, 10%, of austenitic stainless steel foraminous body comprising: (a) compacting water atomized austenitic stainless steel alloy powder in the form of said foraminous body and containing from 0.1% to 10% by weight of prealloyed tin to form a compact; (b) sintering the compact in a dissociated ammonia or synthetic nitrogen atmosphere at a temperature of at least about 1125° C. to a final density less than 80% of theoretical density; and (c) cooling the sintered compact in a dissociated ammonia atmosphere.

Claim 6

A process for improving the corrosion resistance to aqueous nitric acid, 10%, of austenitic stainless steel foraminous body comprising: (a) compacting water atomized austenitic stainless steel alloy powder in the form of said foraminous body and containing from 0.1% to 10% by weight of prealloyed tin to form a compact; (b) sintering the compact in a dissociated ammonia or synthetic nitrogen atmosphere at a temperature of at least about 1125° C. to a final density less than 80% of theoretical density; and (c) cooling the sintered compact in a dissociated ammonia atmosphere.

Claim 7

A process as defined in claim 4 additionally characterized by the step of pickling the foraminous body in dilute aqueous nitric acid.

Claim 8

A process for improving the corrosion resistance to aqueous nitric acid, 10%, of an austenitic stainless steel foraminous body comprising: (a) compacting water atomized austenitic stainless steel alloy powder in the form of said foraminous body and containing from 0.1% to 10% by weight of prealloyed tin to form a compact; (b) sintering the compact in a dissociated ammonia or synthetic nitrogen atmosphere at a temperature of at least about 1125° C. to a final density less than 80% of theoretical density; and (c) cooling the sintered compact.

Claim 9

A process for improving the corrosion resistance to aqueous nitric acid, 10%, of an austenitic stainless steel foraminous body comprising: (a) compacting water atomized austenitic stainless steel alloy powder in the form of said foraminous body and containing from 0.1% to 10% by weight of prealloyed tin to form a compact; (b) sintering the compact in a dissociated ammonia or synthetic nitrogen atmosphere at a temperature of at least about 1125° C. to a final density less than 80% of theoretical density; and (c) cooling the sintered compact.