Effects of Nickel or Copper Addition on Mechanical Properties of Sintered and Carburized Compacts Made of Molybdenum Hybrid-Alloyed Steel Powder

摘要

The effects of Ni or Cu powder addition on the mechanical properties of the sintered and carburized compacts made of the Mo hybrid-alloyed steel powder, which is based on 0.6 mass% Mo prealloyed steel powder diffusion-bonded with 0.2 mass% Mo powder particles, have been investigated. The tensile and rotating bending fatigue strengths of the 1% Ni added material increase compared to the additive-free material. In the case of 2% Ni addition, the tensile strength is almost same and the fatigue strength decreases compared to l%Ni added material. The shrinkage of pores is observed with Ni additions, and should result in the improvement of the fatigue strength. However, more than l%Ni addition forms Ni-rich austenitic phase, which causes the strength reductions. The tensile and rotating bending fatigue strengths decrease with Cu additions. The Cu added material shows the structure including coarse pores formed by outflow of melted Cu during sintering. Such coarse pores should cause the strength reductions.