Partial replacement of chromium in stainless steel

The Bureau of Mines, U.S. Department of the Interior, conducted research on the partial replacement of chromium in stainless steel. The alloys examined contain 8 to 9 pct Cr, 11 to 14 pct Ni, and additions of up to 5 pct Mo, 2 pct Cu, and 2 pct V for corrosion-resistant applications and up to 5 pct Si and 2 pct Al for heat-resistant applications. Molybdenum additions enhanced the corrosion resistance to approach that of type 304 stainless steel (304SS) in H/sub 3/PO/sub 4/, HNO/sub 3/, citric acid, and acetic acid. Alloys with Si and Al additions had 800/sup 0/C oxidation resistance superior to that of type 304SS. The stress rupture resistance of the best Si-Al alloys was comparable to that of type 304SS. The alloys had tensile properties typical of austenitic or martensitic stainless steels, depending on their structures. They exhibited greater tendency to hot/crack during welding than did type 304SS. The research showed that additional levels of Ni, Mn, or C may be needed to stabilize an austenitic structure in these substitutes. The research also showed that additions such as Mo, Si, and Al have potential to substitute for approximately half the Cr in stainless steels for many applications.