STUDY OF SOME ACTIVE WEAR MECHANISMS IN A TITANIUM-BASED CERMET WHEN MACHINING STEELS

This paper discusses the results from a study devoted to the understanding of the wear behaviour of a Ti(CN)-based cermet tool material. Variation in the qualitative and quantitative nature of wear of this tool material in longitudinal turning was effected by the choice of the steel type and cutting conditions. The three work materials (two quenched and tempered steels and one ball-bearing steel) have different microstructures and inclusion contents. The study revealed the presence of conventional flank wear, varying degrees of crater wear and negligible notch wear, while plastic deformation of the cutting edge appears to be the life-limiting factor. Detailed investigation of the active surfaces of the tool revealed abrasion from hard phases and adhesion (micro and macro) to be dominant in the case of the quenched and tempered steel machining, while with ball-bearing steel microchipping, plastic deformation and cracking play an important role. Metallurgical interaction was also observed between the constituents of the tool material and the chip material or reaction products of inclusions, resulting in the embrittlement of the tool material and facilitating rapid wear. The observed differences in the micromechanisms of wear were also in conformity with the variations in the evaluated tool-chip contact stress.