Abstract Republic RSM-300 alloy is an 18% nickel-cobalt-molybdenum age-hardening steel designed to develop up to 300,000 psi yield strength with good toughness. It is recommended for landing gears extrusion dies, rocket motor cases, high-strength bolts, etc. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness and fatigue. It also includes information on low and high temperature performance, and corrosion resistance as well as heat treating, machining, joining, and surface treatment. Filing Code: SA-242. Producer or source: Republic Steel Corporation.