MICROSTRUCTURE OF LASER MELTED-RESOLIDIFIED LAYER ON HIGH SPEED TOOL STEEL

摘要

The laser melted-resolidified processing on W18Cr4V high speed tool steel has been made us-ing a 1 kW CO₂ continuous wave laser device.The microstructure of the laser melted-resolidified layer has been examined by optical microscopy and transmission electronmicroscopy（TEM）.It was characteristic of extremely fine dendrite in the laser melted-resolidified layer and δ-ferrite in bulk form in the center of dendrite.The predominant twinmartensite and a little dislocation martensite existed in the dendrite.The thin plate-likeM₂₁₃C₆ carbide precipitated coherently on the twin martensites along their twin plane.Therewere both austenite rich in W,V and Cr and M₆C carbide in the interdendritic regions.