Quaternary carbonitrides

Carbides, nitrides and carbonitrides belong to a class of hard materials which are very interesting for technical use. This concerns powder particles in so-called cermets, which is a composite material between the hard phase and a metal, as well as the use in hard layers which are deposited in order to protect cutting tools to reduce wear. In order to develop new compounds in this class of materials it is possible to additionally alloy e.g. binary or ternary carbonitrides with another metal carbide, nitride or carbonitride to form a quaternary carbonitride, i.e. the compounds are then composed of two metals as well as carbon and nitrogen. Powders of carbides, nitrides and carbonitrides were mixed, milled in a planetary mill and hot-pressed in order to form an almost completely dense material. This provides that the material properties can be investigated. From such a hot-pressed sample disks and bars were prepared by diamond cutting, boring and grinding/polishing. These samples were subjected to a variety of measurements such as hardness, examination of elastic properties and temperature conductivity. XRD measurements and metallography were performed to investigate the occurrence of phases. For the elastic properties lapped, plane-parallel disks were prepared and the sound transversal and longitudinal velocity was measured. Thus the Young`s, the shear and the bulk modulus together with the poisson ratio could be determined. For most quaternary carbonitrides the obtained data collection is unique, there are no data in the literature. The properties of binary and ternary carbonitrides which represent the boundary phases of the quaternary system were re-investigated for consistency and were found to agree perfect with the data of a previous science foundation project. Data of the most important transition metal carbonitrides could be investigated. Most interestingly, in the system (Ti,Ta)(C,N) a hardness maximum could be observed. For the heat conductivity, the system (Ti,Nb)(C,N) could be found to have the highest values. These values are important for the design of composites and layers and a further step could be performed by preparation of near-commercial materials in order to exploit such behaviour. Another very interesting point was the metallographic and XRD investigation of non-single phase samples. These showed extremely fine precipitates which could be used as ultra-fine powders in nano-hardmetals and cermets.