Carbide Characteristics of High Vanadium High-speed Steel Manufactured by Electroslag Remelting

The carbide characteristics of high vanadium high-speed steel (W3Mo4Cr5V6) manufactured by electro-slag remelting (ESR) are analyzed by field emission scanning electron microscopy (FESEM), electron probe microanalysis (EPMA) and micro-Vickers. The results illustrate that three types of carbides are mainly formed in W3Mo4Cr5V6 which includes the lumpy and strip-like MC in the intracrystalline, lamellar M2C at grain boundary with discontinuous network and globular secondary carbides dispersed in matrix, among these, the eutectic strip-like MC occupies the main part. The more uniform distribution and finer size for both MC and M2C are obtained with high solidification rate (SR). Both 2D and 3D morphologies of MC carbides show obvious symmetry with clustered distribution and various shapes. The MC and M2C are rich in V and Mo, W respectively, the compositional characteristics are not only related to the carbide type and morphology, but also the precipitation order and distribution density. The Vickers hardness of primary MC, eutectic MC and M2C are measured and the average values are 2 205 HV, 850 HV and 896 HV respectively which includes the adverse effects of soft matrix on the test results of hard carbides. A new and exact test method for pure carbides should be developed in the future.