Fabrication And Tribological Research Of Ti₃SiC₂/NiCr Composites

Ni-20Cr alloys have excellent high-temperature mechanical properties, oxidation resistance and corrosion resistance, making them promising high-temperature self-lubricating composites. Ti3SiC2is a new ceramic and is now become a focus because it both has the properties of ceramic and metal material, such as low density, high melting point, nice electrical and thermal conductivity, high elastic modulus, high fracture toughness, oxidation resistance, thermal shock resistance and machinability. And more significantly, it has very low friction coefficient and nice self-lubrication properties. Ti3SiC2can be a promising ceramic reinforcement for Ni-20Cr. So the introduction of Ti3SiC2to the matrix will exert the effect of dispersion strengthened nickel alloys, making the composites exhibit more excellent properties.On the basis of high pure Ti3SiC2powder preparation, Ti3SiC2/NiCr composites are prepared by pressless sintering and spark plasma sintering. We test its relative density、hardness、tribological properties and so on, and composition、structure and properties of the Ti3SiC2/NiCr compound materials are studied on through XRD、 SEM and EDS.The relative density of Ti3SiC2/NiCr compound materials is about90%, which is fabricated by pressless sintering. The hardness increases with the growing of the contents of Ti3SiC2and reaches a maximum value of194HV1with the20wt%Ti3SiC2. The decomposition of Ti3SiC2happens during the sintering process and TiC is producted. And Si might be solving in Ni-20Cr formation which is lead to the diffraction peak of NiCr alloys shift left. The degree of left shift of the diffraction peak enhanced with the growth of the contents of Ti3SiC2. The conjunction and interface of Ti3SiC2/NiCr compound materials is studied. The results show that the interlayer between Ni-20Cr and Ti3SiC2will be formed obviously. But the composition structure and formation mechanism of the interlayer need further studying. The friction coefficient becomes smaller as the loads and sliding speed becomes larger, but the wear rate is reversed. The wear rate becomes smaller with the growth of the contents of Ti3SiC2and variation of the friction coefficient is different. It also discusses the wear mechanism.Compared with pressless sintering, the relative density and hardness of the composites which are sintered by SPS and contains20wt%Ti3SiC2get the very big increasing. The relative density is more than98%and the hardness is848HV1which is largest when the composites are sintered at1000℃by SPS. The decomposition of Ti3SiC2also happens during the sintering process and TiC is producted. And Si might be solving in Ni-20Cr formation which is lead to the diffraction peak of NiCr alloys shift left. The degree of left shift of the diffraction peak enhanced with the growth of the sintering temperatures. The friction coefficient becomes smaller as the loads and sliding speed becomes larger, but the wear rate is reversed. Furrow and exfoliation exist on the wear surface under different loads. At different sliding speed, the wear mechanism changes from adhesive wear and abrasive wear to abrasive wear mainly.