Study On Preparation And Friction And Wear Properties Of Ti₃AlC₂/Za Composites

Zinc-Aluminum alloys (ZA alloys) are widely used in bearings, shaft sleeve, bearing shell because of its excellent mechanical properties, high abrasion resistance and the lower raw material cost. Zinc-Aluminum alloys are important bearing materials, especially suitable for high-load and low-speed applications. To a great extent, its poor heat resistance performance restricts the scope of ZA alloys application. In order to further improve the strength, hardness, wear resistance and heat resistance performance, since the1980s, materials research workers at home and abroad has developed zinc alloy matrix composite which reinforced by ceramic particles, whisker and fiber. But due to the thermal mismatch between matrix and reinforcing phase, the strengthening effect is not significant. This paper selects Ti3AlC2particles to reinforce zinc-aluminum alloy. Ti3AlC2exhibits an excellent comprehensive property of metals and ceramics, and it can be used as a new type of reinforced phase for zinc matrix composites. In this study, different compositions of Ti3AlC2/ZA27composites are prepared by means of powder metallurgy process. The relative density, hardness, bending strength, tensile strength, friction and wear performance were tested in order to do some exploratory experiments. The microstructure and phases of the composites were analyzed by using X-ray diffraction, scanning electron microscopy and EDS.In this paper, Ti3AlC2/ZA27composites are prepared by pressureless sintering a mixture of Ti3AlC2and ZA27powders. First, studied the influence of technological parameters on the material preparation and properties of the composites. The results show that with the increase of sintering temperature, the relative density of composites increased from85.72%at650℃to92.56%at870℃, and the hardness increased from88.2HV at650℃to133.6HV at870℃. With the extension of heat preservation time, the relative density and hardness of the composites have reached the maximum at150min, the maximum is92.65%and133.6HV. So in the experimental range, Pressureless sintering optimum process conditions of preparation of Ti3AlC2/ZA27composites is: under the argon gas protection, according to the heating rate of20℃/min, the furnace temperature is℃, heat preservation is150min.Ti3AlC2/ZA27composites which volume fraction is from10%to40%are prepa-red by pressureless sintering at870℃for150min in Argon atmosphere. Study the influence of material composition on properties of the composites. Significant strength- ening effects are observed after incorporation of Ti3AlC2particles to form Ti3AlC2/ZA27composites. With the increase of the content of T13AIC2particles reinforced phase, the vickers hardness increased from96.7HV to142.3HV, increased47%. The bending strength and tensile strength increases and then decreases. When the content of Ti3AlC2particles is30%, the bending strength and tensile strength reached the maximum497.3MPa and294.7MPa.Ti3AlC2/ZA27composites show good tribological properties and wear resistance during oil lubrication sliding against a45#steel disk. The results show that, at a sliding speed of3m/s under normal loads0.6MPa, with the increase of the content of Ti3AlC2particles reinforced phase, the friction and wear properties of composites continuously improved. In a range of0-30vol.%, friction coefficient from0.2968to0.1307, wear rate from2.38×10-4mm3/N·m to0.93×10-4mm3/N·m. Compared with the ZA27matrix, the friction coefficient of30vol.%Ti3AlC2/ZA27composites fell down to56%and the wear rate decreased to60.9%. Added Ti3SiC2particles in the ZA27matrix can also effectively improve the wear resistance of the composites and reduce the friction coefficient. Compared with the ZA27matrix, the friction coefficient of30vol.%Ti3SiC2/ZA27composites fell down to4.5%and the wear rate decreased to34.5%. But its effect is not better than Ti3AlC2. At a sliding speed of3m/s, along with the normal loads increases from0.1MPa to0.6MPa, the friction coefficient of material decreases, and the wear rate increased. SEM investigating show that sticking friction, oxidize friction and grain-abrasion are all taking effect in the friction procsse of Ti3AlC2/ZA27and the sticking friction is the most important friction form.