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

Abstract

The carbide characteristics of high vanadium high-speed steel (W3Mo4Cr5V6) manufactured by electroslag 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 2205 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.