External Stress Effect on Microstructure and Transformation Plasticity of Hot Work Tool Steel During Quenching

The article presents the investigation of plasticity and microstructure of hot work tool steel during martensitic transformation. Specimens were austenized, then air quenched. During cooling process the specimens were bent under 100 MPa stresses. There were three types of loading during cooling: continuous bending straight after withdrawing of sample from furnace (deformation of initial austenite, and then martensite formation under stresses); bending when martensitic transformation started (deformation of martensite); unloading when martensitic transformation started (main deformation of austenite – measurement of self-deformation). Plastic deflection of bending samples was measured during cooling until room temperature. The incoming martensitic transformation of the material showed significant increasing of plasticity. As bending caused two types of stresses – tensile and compression, its different influence on martensitic transformation was detected by specimen self-deformation. The microstructure of the stretched and compressed surfaces of the samples was determined by XRD, SEM, and EDS methods.