Abstract: Surface oxygen infiltration products and hardness of the pure tantalum used as artificial joints under different processes were studied by means of low pressure vacuum surface oxygenation technology, scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and nanoindentation technology. The results show that surface oxygen infiltrated layer with thickness of about 3.6 μm, which contains the phase of tantalum oxide Ta₄O, can be prepared under the condition of 500 ℃×2 h/273 mL(oxygen flow volume, the same below). The δ-(Ta, O) compounds can be prepared under the conditions of 550 ℃×2 h/273 mL, 550 ℃×5 h/1.3 mL, 550 ℃×10 h/0.013 mL and 650 ℃×3 h/0.013 mL. The thickness of surface oxygen infiltrated layer with δ-(Ta, O) compounds varies according to the parameters of oxygen infiltration temperature, time and oxygen flow volume. The surface oxygen infiltrated layer with the average thickness of nearly 60 μm is prepared under the condition of 550 ℃×1 h/273 mL, and the surface phase is tantalum oxides with polyvalent tantalum, the Vickers hardness and maximum nanoindentation hardness of the specimen are (160.27±2.80) HV5 and 7.92 GPa, respectively, which are significantly higher than those of the pure tantalum. This technology can be used to increase the abrasion resistance and lifespan of the Ta-based artificial joints.

Key words: pure tantalum, surface oxygenation, tantalum oxides, thickness, hardness