对M42高速钢刀具进行脉冲磁化处理, 考察脉冲磁场对组织和性能的影响, 分析了脉冲磁场改变微观组织以及力学性能作用机理. 运用TEM和激光共聚焦显微镜分析了脉冲磁场冲击前后高速钢位错组态、碳化物分布以及微观组织的变化. 研究表明, 高速钢经脉冲磁化处理后, 发生晶格畸变, 基体内析出大量弥散碳化物, 微观组织变细密, 晶粒细化. 微观组织的变化导致力学性能发生变化, 材料Rockwell硬度与显微硬度均显著提高, Rockwell硬度最大可以增加2.9 HRC. 基于位错理论分析了脉冲磁场作用下高速钢的强化机制, 磁场作用于位错的力足以克服位错线张力引起的阻力和晶格点阵引起的阻力, 从而使位错能以Orowan机制产生增殖、滑移, 致使位错密度增加.

Magnetic treatment of tools is a novel method to increase tool life in which the tool is magnetized before cutting or the cutting is performed in a magnetic field. The method has many attractive features, such as short treatment time and no pollution. However, this approach has not been widely applied yet, since the mechanism of magnetic treatment of tools is not clear and treatment results are affected by many factors. Therefore, it is important to study the mechanism of magnetic treatment of tools. This work aims to study the influence of pulsed magnetic treatment on microstructures and mechanical properties of M42 (W2Mo9Cr4VCo8) high speed steel, which is a typical tool material which contains high amounts of cobalt. So it can show a stronger magnetism in the process of pulsed magnetic treatment. Changes of dislocation configuration, carbide distribution and microstructure before and after magnetic treatment were characterized by TEM and laser scanning confocal microscope. Moreover, Rockwell hardness and micro-hardness were measured to quantitatively investigate the influence of magnetic treatment on the mechanical properties. Results showed that after pulsed magnetic treatment the lattice of material was distorted, the carbide was precipitated, and the microstructure and crystalline grain were refined. The changes of microstructure led to changes of mechanical properties, of which the Rockwell hardness and micro-hardness were significantly increased. The maximum increase of Rockwell hardness was 2.9 HRC. Ultimately, the strengthening mechanisms of high speed steel were analyzed based on dislocation theory. It was shown that the subjected force of dislocations due to the magnetic treatment could overcome the centripetal restoring force and the Peierls stress of dislocations. Therefore, dislocations proliferated by the Orowan dislocation strengthening mechanism, and dislocation density increased. The dislocation configuration determined from TEM micrographs was in good agreement with the discussion of dislocation mechanisms.