Abstract
The effect of copper powder addition on properties of sintered and case-hardened compacts made of the 0.45 mass% Mo prealloyed steel powder has been investigated. The tensile strength of sintered and case-hardened compacts made of the powder increased with 1 mass% Cu addition, but leveled off with 2 mass% Cu addition. The rotating bending fatigue strength of sintered and case-hardened compacts made of the powder increased with 1 mass% Cu addition. However, the fatigue strength decreased with 2 mass% Cu addition and was lower than that of Cu free material. The tensile and fatigue strengths of sintered and case-hardened compacts made of the powder with 1 mass% Cu addition are equal to those made of the conventional 4 mass% Ni diffusion-alloyed steel powder. The reduction of fatigue strength with 2 mass% Cu addition should be attributed to an increase in size of the maximum pore due to Cu liquid phase and probably an increase in fatigue crack growth rate due to Cu addition.
