医用Ti6Al7Nb合金氧化行为及其磨损性能

为提高生物医用Ti6Al7Nb合金表面的耐磨损性能,研究了在500~800℃空气中的热氧化行为以及其改善的磨损性能.研究结果表明:500~600℃氧化速率低,表面硬度较基体变化不大.在750℃以上,氧化速度增加,氧化动力学遵从抛物线规律,氧化物主要由TiO2和少量Al2O3组成.在800℃时,氧化物颗粒长大,氧化层疏松,极易剥落.综合考虑硬化层深度和氧化时间,得出最佳热氧化工艺参数为750℃氧化8 h.在此工艺下处理的钛合金表面硬度达到1 047 HV,耐磨性是原合金材料的280倍.分析了合金氧化后耐磨损性能的提高机制.

Oxidation Behavior and Wear Resistance of Biomedical Ti6Al7Nb Alloy

In order to improve the surface wear resistance of the biomedical titanium alloy Ti6Al7Nb, the oxidation behavior was studied in air at 500-800°C for 2-12 h and then its improved wear resistance was tested at room temperature. The testing results indicated that the oxidation rate is low at 500-600°C, and the oxidized surface hardness changes little in comparison with the hardness of the alloy matrix. When the temperature exceeds 750°C, the oxidation rate increases and the oxidation kinetics follows the parabolic rule. The oxides mainly consists of compact TiO2 with small amount of Al2O3. At 800°C the oxide particles grow rapidly, thus resulting in a loosened oxidized layer where the spalling effect frequently happens. Taking account of both the depth of hardened layer and oxidizing time, the optimum oxidization parameters are determined to be 750°C/8 h. By such an oxidization schedule, the surface hardness comes up to 1047 HV, especially the wear resistance is greater than 280 times that of original material. The mechanism of wear resistance improvement after oxidation is analyzed in detail.