Structure and phase transformations of AISI M2 high-speed tool steel treated by PIII and subsequent compression plasma flows of nitrogen

The effect of ‘double’ treatment (plasma immersion ion implantation and subsequent compression plasma flows) on microstructure, element and phase composition, as well as on microhardness properties of AISI M2 high-speed tool steel has been studied. Such methods as Auger electron spectrometry (AES), X-ray diffraction (XRD), energy-dispersive X-ray (EDX) microanalysis and scanning electron microscopy (SEM) allowed us to obtain the data suggesting that under such treatment a martensite-austenite conversion and the formation of a deep (approx. 35 μm) three-layered structure take place. It has been established that transformations of near-surface regions are associated with the complete dissolution of the initial (Fe, Cr)3(W, Mo)3C carbide (≤5–10 μm) and the formation of γN,M expanded austenite doped with atoms of nitrogen, carbon and alloying metals M=W, Mo, Cr.