Mechanical properties, corrosion behavior and in-vitro bioactivity of nanostructured Pd/PdO coating on Ti–6Al–7Nb implant

• Mechanical and corrosion behavior of Pd/PdO coating on Ti67Nb was explored.
• During annealing at 650 °C, crystallization of the as-prepared coating occurred.
• Due to the surface modification, an improvement in the hydrophilicity was recognized.
• The 650 °C annealed coating had the highest corrosion protection efficiency.
• A thick layer of apatite was observed after immersion in SBF for 14 days.

A balanced combination of mechanical properties together with a high corrosion protection are the essential requirements for a successful joint arthroplasty. In an attempt to improve the mechanical properties and corrosion resistance of Ti–6Al–7Nb implant (IMPTi67), a thin coating of Pd/PdO was developed by physical vapor deposition magnetron sputtering (PVDMS) and subsequent annealing at a low heating rate over a range of temperatures for 1 h. Corrosion behavior of the coatings was examined in phosphate-buffered saline (PBS) using potentiodynamic polarization. The results showed that surface wettability, mechanical properties as well as corrosion resistance of IMPTi67 were significantly influenced by the surface chemistry and roughness. The as-sputtered film showed a cubic structure with (111) preferred orientation, while a highly crystalline Pd/PdO thin film with a good adhesive strength was formed after the subsequent annealing at 650 °C, thereby an improvement in hydrophilicity was detected. From the nanoindentation tests, Young's modulus and hardness of the coating after annealing at 650 °C reached 56 and 3 GPa, respectively. The polarization curves showed that the resultant coated IMPTi67 had significantly enhanced corrosion resistance compared with untreated substrate. The nanostructured coatings showed drastically improved in-vitro bioactivity in simulated body fluid (SBF).

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