Lower-Cost, Ultra-High-Strength, High-Toughness Steel

Abstract

A non-stainless steel alloy includes, in combination by weight, about 0.20% to about 0.33% carbon, about 4.0% to about 8.0% cobalt, about 7.0 to about 11.0% nickel, about 0.8% to about 3.0% chromium, about 0.5% to about 2.5% molybdenum, about 0.5% to about 5.9% tungsten, about 0.05% to about 0.20% vanadium, and up to about 0.02% titanium, the balance essentially iron and incidental elements and impurities.

What is claimed is: 
     
         1 . A non-stainless steel alloy comprising, in combination by weight:
 about 0.20% to about 0.33% carbon, about 4.0% to about 8.0% cobalt, about 7.0% to about 11.0% nickel, about 0.8% to about 3.0% chromium, about 0.5% to about 2.5% molybdenum, about 0.5% to about 5.9% tungsten, about 0.05% to about 0.20% vanadium, and titanium up to about 0.02%, the balance essentially iron and incidental elements and impurities said alloy having a microstructure characterized by MC grain refinement particles by inclusion of principally M 2 C carbide particle precipitates wherein M 2  is comprised of one or more elements selected from the group consisting of chromium (Cr), molybdenum (Mo), tungsten (W), and vanadium (V) in a predominately lath martensite matrix, said alloy further characterized by the combination of high strength, high fracture toughness (Klc) and enhanced stress corrosion cracking resistance (Klscc).   
     
     
         2 . The alloy of  claim 1 , wherein the alloy comprises, in combination by weight decreasing amounts of molybdenum, chromium, tungsten and vanadium.