Study on the production of 2mass%Ni-Fe sintered parts using Zr pre-alloyed, water-atomized powder

2mass%Ni-Fe sintered parts are, at present, produced by premixed method using carbonyl iron powder and carbonyl nickel powder as principal raw materials. In this study, the production method of sintered parts using Zr pre-alloyed and water atomized 2mass%Ni-Fe alloy powder as raw material was investigated. Followings were observed; By pre-alloying with about 0.8 mass% of Si, Zr pre-alloyed 2mass%Ni-Fe alloy obtained the sintered density comparable to the conventional premixed method. The Si pre-alloying increased the surface energy of powder, and the activated surface diffusion, and thereby promoted formation of necks. The addition of carbon as alloying element obstructed the densification in lower sintering temperature, but, in higher temperature, promoted the densification by consuming oxygen with C-O reaction. The sintered parts of Zr and Si pre-alloyed 2mass%Ni-Fe alloy powder contained not only less pores and inclusions but also uniformly-sized grains. These resulted in higher values of tensile strength and hardness but lower elongation. By carburizing and quenching, the sintered parts of Zr and Si pre-alloyed 2mass% Ni-Fe alloy powder showed mechanical properties and hardness higher than those of the conventional premixed method. These values were controllable with adjusting of tempering temperature.