Evolution of microstructure of instrumental AISI M2 steel after plasma immersion nitrogen and carbon implantation

Investigations of the elemental and phase composition, microstructure, micr ohardness and tribological properties of AISI M2 steel subjected to nitroge n and carbon plasma-immersion ion implantation (PIII) at different regimes are presented. Elemental composition was studied by Auger electron spectros copy (AES) and X-ray microanalysis. Phase composition was identified by mea ns of conversion electron Mossbauer spectroscopy (CEMS) and X-ray diffracti on (XRD). Using these methods it was established that nitrogen PIII at a ta rget temperature of 380 degreesC resulted in phase transformations: from al pha'-Fe(C,M) + M6C + MC (M: Fe,Cr,W,Mo) to epsilon-(Fe,M)(2+x)(N,C)+ M-6(C) . With increasing temperature up to 500 degreesC in nitrogen PIII the retai ned martensite, in addition to epsilon-(Fe,M)(2+x)(N,C), was observed. Join t nitrogen and carbon PIII leads to the formation of epsilon-(Fe,M)(2+x)C a nd (Fe,M),C, (M:Cr,W,Mo) carbides. Theoretical analysis of the distribution of thermoelastic stresses during PIII demonstrated the essential increase in the mass transport process of implanted atoms into the target volume. On the basis of the estimations conducted, it has been shown that migration p rocesses of nitrogen into steel during PIII have a complicated character an d can be described with the help of mechanisms stimulated by the reaction o f a crystal lattice under the impulse influence. (C) 2001 Published by Else vier Science B.V. All rights reserved.