1.25C 7.9Ni-0.3Mo-0.4Cr Low Alloy Steel

This is a high-carbon, nickel-rich low-alloy steel with significant cobalt content (3.69%), designed to achieve very high strength through precipitation hardening and martensitic transformation. The composition—dominated by iron with 7.86% nickel, 1.25% carbon, and cobalt as a strengthening addition—represents a specialty alloy used in applications demanding extreme hardness and wear resistance combined with some toughness. Such alloys are employed in demanding tool and die applications, aerospace components requiring high strength-to-weight ratios, and specialized bearing or fastener systems where conventional steels fall short; the cobalt and nickel additions improve both high-temperature strength retention and fatigue performance compared to plain carbon steels.