Studies On Microstructure And Mechanical Properties Of Ti C-based Cermets Bonded By Ni_75-xAl_25+x

As a intermetallic compound, Ni3 Al has many good porperties, such as high melting point, high hardness, outstanding wear resistance and oxidation resistance, especially the character that its yield strength raised with the temperature increasing below 950?. In this paper, mechanical alloying was adopted in preparation of Ni_75-xAl_25+x powders with different atomic ratio, and those powders were used as the binder of TiC-based cermets with mulity components. In order to study the microstructure and mechanical properties at room temperature of TiC-based cermets bonded by Ni_75-xAl_25+x intermetallic compound, the X-ray diffraction?XRD?, scanning electron microscopy?SEM?, energy dispersive spectroscopy?EDS?, traverse rupture strength tester and Rockwell hardness and Vickers hardness tester were applied.The Ni_75-xAl_25+x?-4at.%?x?6 at.%? intermetallic compound with little B addition was produced by mechanical alloying used the raw powders of Ni and Al with little B addition. During high-energy milling, with repeating crushing-cold welding the crystal defects and surface energy of Ni and Al increased by repeating crushing-cold welding, the Al atom diffused into Ni forming disordered Ni?Al? solid solution firstly and then the powde mixture transformed to Ni_75-xAl_25+x intermetallic compound on further milling.With the increasing of liquid–phase sintering temperature the linear shrinkage of cermets increased and the densification of cermets was enhanced, while the possibility of core phase particles growth was also increased. Generally, the TiC grain showed a weak “core-rim” structure, after the liquid–phase sintering, and the rim phase was incomplete. When the change of Al content in Ni_75-xAl_25+x is from x=-1 to x=2at.%, the TiC grains size is smaller and embedded in binder phase uniformly with density microstructure.With the increasing of Al content, the mechanical properoties of TiC-based cermets bonded by Ni_75-xAl_25+x such as transverse rupture strength, Rockwell hardness and fracture toughness were increased firstly and then reduced, the cermets gain the best mechanical properties at room temperature when the variation of Ni_75-xAl_25+x is-1at.%?x?2 at.%. When the sintering temperature is 1470?, the transverse rupture strength of TiC-based cermets reaching the peak values. The mechanical properties of TiC–25Ni75-xAl25+x –20WC–10Mo2C–0.8C?wt.%? sintering at 1470? with 1h liquid–phase sintering is that: transverse rupture strength 1346 MPa, hardness 90.5?HRA? and fracture toughness 11.48MPa·m1/2?KIC?.