DEVELOPMENT OF DIFFUSION-ALLOYED POWDERS USING Cu-Ni DIFFUSION-ALLOYED PARTICLES ON Fe AND Fe-Mo BASE MATERIALS

摘要

Diffusion-alloyed powders have the advantages of the blended powders (high compressibility) but with a low level of segregation, keeping some of the advantages of the fully alloyed powders. The main problem of conventional Cu-Ni-Mo diffusion-alloyed powders is the use of Ni as raw material (typically nickel carbonyl grade is used to alloy these powders) and its problems as harmful material due to its low particle size. With the aim of drastically reducing the risks of the addition of fine nickel powders, the production of the diffusion-alloyed powders is made with a fully pre-alloyed Cu-Ni alloy of a bigger size; at the same time, the behaviour of the diffusion paths in the sintering step is modified. In this work, a fully prealloyed 69% Ni-31% Cu (from Hogands AB) was mixed with plain iron and Fe-0.85% Mo (ASC 100.29 and Astaloy85 grades respectively, Hoganas AB) to obtain diffusion alloyed powders with the following final composition: Fe-2.5% (wt.) NiCu and Fe-0.85%Mo-2.5% (wt.) NiCu. All materials were mixed with 0.6% of graphite, pressed at 700 MPa floating die system and sintered at 1120 °C during 30 minutes in N_2-10%H_2-CH_4 atmosphere. After sintering, steels were quenched in oil from 950°C. Tempering was made at 250°C during 40 minutes. All the obtained materials were mechanically tested through tensile test and hardness measurements, as well as proceeding with the metallographic study.