| Considering the working conditions of light Ti Al alloy as high temperature structural components, research on friction and wear properties is significant. Aiming at the poor research of high-temperature tribological properties of Ti Al alloys and Ti Al-based composite, Ti, Al and Ti N powder was used as raw material, in-situ synthesized two kinds volume fraction Ti2 Al N/Ti Al composites by the method of hot pressed sintering, respectively 15 vol.% and 35 vol.%, cast Ti-48Al-2Cr-2Nb as a contrast. Based on characterization of tissue structure and mechanical properties, this study focuses on the friction and wear properties of this three kind of materials at different temperatures, further studied the effect of surface thermal oxidation to friction and wear properties of. Ti2 Al N/Ti Al composite.Microstructure and mechanical properties analysis showed that comparing with the fully lamellar structure of Ti Al alloy, the matrix of two composites showed nearly lamellar structure; the reinforcing phase of 35 vol.% composite agglomerated around matrix; present a network distribution. Ti2 Al N displayed a good enhancement at room temperature, bending strength of each composites is greater than Ti Al alloy, hardness and bending modulus enhanced with the volume fraction of reinforcing phase increases, the relative weak bonding between Ti2 Al N particles at 800 ℃ diminished the bending strength of 35 vol.% composite.Friction and wear test results showed that the three materials have low wear resistance at low-temperature, but the glaze layer formed at 600℃ because of oxide particles piled up in the wear surface and the oxide layer formed at 800℃ because of self-oxidation lagerly enhanced the wear resistance. Compared with Ti Al alloys, Ti2 Al N/Ti Al composite formed oxide layer on the wear surface from room temperature to 400 ℃, has excellent tribological properties. At 600 ℃,the present of Ti2 Al N is beneficial to the formation of the glaze layer, at 800℃, Ti2 Al N acted as supporting body and protected the oxide layer. The composite contained Ti2 Al N had better wear resistance at both 600℃ and 800℃ compare with Ti Al alloy..Ti2Al N with poor oxidation resistance, is bad for improvement of oxidation resistance of the composite. Oxidized 2h at 820℃can obtained the mixed oxide layer of Ti O2+Al2O3. At 920℃, with the increase of oxidation time, the structure of the thermal oxide layer on composite surface from Ti O2/Ti O2+Al2O3 mixed layer gradually becomes Ti O2/Al2O3/Ti O2+Al2O3 mixed layer. Comparing with Ti O2 and Al2O3 layer, the mixed layer growed faster.Surface thermal oxidation can significantly improve the wear resistance of composite in low-temperature, the wear resistance of surface oxide layer reduce with the temperature rising. Oxide layer softening and easy to fall off at 600℃, on the contrary, wear resistance is poorer than the composite which is not oxidized. Polished the thermal oxide layer to obtain different surface thermal oxide layer, the results show that the special growth of Ti O2 layer(sharp, and a gap exists between the particles) is the main reason for the weight increase after wear, Generally speaking, Ti O2 layer has good wear resistance, while the mixed layer has the lowest friction coefficient. |
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