Preparation Of Functional Gradient Ti(C,N)-based Cermets Material

Ti(C,N)-based cermets have been introduced into the field of cutting tools not only because of their high hardness, wear resistance, oxidation resistance, phase stability, low thermal expansion coefficient which are necessary for high temperature processing, but also for its reasonable toughness and strength. At the beginning of this thesis, The developmental process have been outlined,the performance and present research situation of the cermets tool as well as the coating cermets tool have been summed up, several common used method of coating are simply introduced, in the end of the paper the developmental trend has also been pointed out. Composition of 10%TiN-36.2%TiC-32%Ni-13%Mo-7.0%WC were used to prepare the sintered body. The sintering temperature are 1405℃,1415℃,1425℃, 1435℃,it is found that 1415℃is the best sintering temperature. Simples sintered at this temperature have the highest TRS and density. Fracture analysis diagram is rock-candy structure, the coarse hard-phase and the pores which cause the abruption. The EPMA was used to check element's distribution. The titanium, tungsten, nitrogen and carbon contents are constant all through the as-sintered material. HIP technology was used to preparation Ti(C,N)-based cermets functional gradient material. SEM, OM, EPMA, TEM and other techniques were used to analyze the porosity, microstructure , fracture pattern as well as the element distribution and the performance was compared. The results indicated: cermets cutting from propagating into the substrate, thereby, tool life would be highly prolonged. The high nitrogen activity in the surface region was the driving force to formate the N-rich carbonitride in the near-surface zone. It is the high pressure high temperature of HIP technology that reduced the pores and the surface micro-crack, this is the reason why the surface performance such as hardness will be improved obviously. inserts nitrited by use of this process have a golden-yellow coating comprising pure titanium nitride,the thickness is 4μm. The X-ray diffraction analyze found the golden phase is TiN. The nitridation process does not cause a decrease in transverse rupture strength and toughness of cermets which is very important from the viewpoint of their lower toughness and higher brittleness compared with conventional WC-based cemented carbides. And this has a good correspondence with this experiment results. And the tough surface layer shall prevent cracks in the brittle coating. A reasonable technology of preparation of gradient hard coatings by multi-arc ion plating was introduced. X-ray diffraction analysis was done to define the phase which generated after multi-arc plating. It was found that pure TiN films were appeared on the substrate. Microstructure, micro-hardness, transverse rupture strength as well as the cohesion were measured. The results show that gradient hard coatings were existed on cermets substrate and the cohesion is ideal. Surface hardness improved while the transverse rupture strength preserved.