Analysis of Cracking Causes of W6Mo5Cr4V2 Steel for Machining Tools
The cracking causes of W6Mo5Cr4V2 steel used in machining tools were analyzed through mac-roscopic inspection,chemical composition analysis,hardness testing,metallographic examination and SEM morphology analysis,etc.The results showed that the main cause of tool cracking was that the failed machi-ning tools exhibited the microstructure with discontinuous reticular and aggregated polyhedral carbides,as well as inadequate quenching due to improper subsequent heat treatment processes.The transition zone between the hardened and unhardened regions,as well as the concentration areas of reticular and aggregated polyhedral carbides in the core region,generated large stress concentration.During grinding process or improper operations,the tensile stress on the surface exceeded the tensile ultimate strength of the material,and under the influence of internal quenching stresses,cracks was initiation and propagation,ultimately leading to tool breakage.
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