Properties of the Fe-30Cr-20Co-Mo Hard Magnetic Powder Alloy with Increased Porosity

The effect of the sintering medium (vacuum and argon) on the structural and magnetic characteristics of magnetically hard alloy Fe-30Cr-20Co-Mo with increased porosity (about 4%) has been studied. The material is synthesized by powder metallurgy. The entire porosity of the material is of the closed type. Powders of pure elements are used to synthesize the alloy. The samples were sintered at a temperature of 1140 degrees C for 150 min in vacuum and argon. Alloy samples are studied in three states: after sintering, after quenching, and after heat treatment with the purpose of gaining magnetic properties. Sintering in argon increases the density of samples by approximately 0.3% compared to samples sintered in vacuum. Despite the lower density, the material sintered in vacuum has slightly stronger magnetic properties compared to the material sintered in argon. Hardened alloy samples have substantially higher plasticity compared to the materials after sintering and after heat treatment. Hardened samples are deformed without fracture at a deformation of more than 60%. Quenching simultaneously reduces the yield strength. Samples after sintering have the lowest plasticity (about 10%), which is approximately three times less than the plasticity of the sample after heat treatment. There is a good correlation between yield strengths and hardness values. Specimens with higher yield strengths also have higher hardness values. The grain size of the material sintered in vacuum is almost the same as the grain size of the material sintered in argon. Their grain size is about 30 mu m. Irregularity is not observed, which indicates that no secondary recrystallization process occurs. Anisotropy is also not observed. Thus, it is experimentally established that the Fe-30Cr-20Co-Mo alloy can be sintered both in vacuum and in argon. In both cases, the mechanical and magnetic properties are approximately at the same level acceptable for technical applications.