Свойства магнитотвердого порошкового сплава Fe – 30 Cr – 20 Co – Mo с повышенной пористостью

Abstract

The purpose of this work is an experimental study of the influence of the sintering environment (vacuum and argon) on the structural and magnetic characteristics of the Fe – 30 Cr – 20 Co – Mo magnetically hard alloy with increased porosity. The material was synthesized by powder metallurgy. In the present work, studies were carried out on materials with a porosity of about 4 %. All porosity of the material was closed. Powders of pure elements were used to synthesize the alloy. The samples were sintered at a temperature of 1140 °C for 150 minutes in vacuum and argon. The experiments were carried out on materials in three states — after sintering, quenching material and material after heat treatment to obtain magnetic properties. Sintering in argon increases the density of samples by approximately 0.3 % compared to samples sintered in vacuum. Vacuum sintered material has slightly higher magnetic properties compared to argon sintered material, despite the lower density. Hardened samples have significantly higher plasticity compared to materials after sintering and after heat treatment. Such samples are deformed without fracture at a deformation of more than 60 %. Hardening simultaneously reduces the yield strength. Samples after sintering have the lowest plasticity (about 10 %), approximately three times less than after heat treatment. There is a good correlation between yield strength values and hardness data. For specimens with higher yield strengths, there are also higher hardness values. The grain size of the material sintered in vacuum is almost the same as the size of the material sintered in argon. Their size is about 30 µm. Irregularity is not observed, which indicates that the process of secondary recrystallization did not occur. Anisotropy is also not observed. Thus, it was experimentally established that the Fe – 30 Cr – 20 Co – Mo alloy can be sintered both in vacuum and in argon. In this case, the mechanical and magnetic properties are approximately at the same level acceptable for technical applications.