Optimization of Chemical Composition and Heat Treatment of High-Carbon Iron Alloys with 14% Chromium and 3% Vanadium

Abstract

A series of iron alloys for wear applications containing 14 %Cr, 3 %V and 1.5 to 4.2 %C is investigated in as-cast and quenched condition. In almost all alloys carbide phases were hexagonal M7C3 and cubic VC carbides. Critical points of the alloys were determined dilatometrically; cooling from 1000 °C at a rate of 0.4 K/s results in diffusional decomposition of austenite, and at the rate of 15 K/s (air) - in martensitic transformation. The experiments on modifying the alloys with 0.1–0.5 %Ce showed that cerium refines the structure at the concentrations not exceeding 0.3 %Ce. Strength and wear resistance reach maximum at ~ 0.2–0.3 %Ce, and alloy hardness is not significantly affected. Heat treated (quench hardened) alloys show typical behaviour of high-carbon ledeburitic alloys, viz. hardness as a function of quenching temperature reaches maximum when the amount of retained austenite is increased. The greatest hardness of 68.5 HRC is achieved in the 3.5 %C alloy, which also has the highest wear resistance. A method of phase composition and hardness calculation for high-carbon alloys based on thermodynamic description of ternary system Fe–Cr–C is presented; the calculation results align with the experimental data.