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<p>Hydroxyapatite (HA) and functionally graded HA-Al<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub> coatings were deposited on Ti-6Al-4V alloy via plasma spraying, followed by heat treatment at 750&#xa0;°C for 2&#xa0;h. The effects of compositional gradation and heat treatment on microstructure, corrosion behavior, wettability, surface energy, and in vitro bioactivity were systematically evaluated. Both coatings exhibited porous, rough surfaces conducive to osseointegration, with heat treatment reducing roughness (HA: 3.5 to 3.0 µm; graded: 3.9 to 3.54 µm) and porosity (HA: 20 to 17%; graded: 25 to 20%). Corrosion studies showed that the post-heat-treated graded coating had a more noble corrosion potential (Ecorr =  − 0.12 V) and a reduced corrosion rate (2.71 × 10<sup>−2</sup>mm/year) compared to as-sprayed graded (E<sub>corr</sub> =  − 0.18&#xa0;V, corrosion rate − 3.60 × 10<sup>−2</sup>&#xa0;mm/year) and HA coating (E<sub>corr</sub> = -0.25&#xa0;V, corrosion rate − 4.57 × 10<sup>−2</sup>&#xa0;mm/year). Polarization resistance and EIS confirmed superior stability, with post-heat-treated charge transfer resistance versus HA. Improved corrosion resistance is attributed to densification, reduced porosity, and the barrier effect of Al<sub>2</sub>O<sub>3</sub> and TiO<sub>2</sub>. Wettability improved (contact angles 35-42° vs. 60° for bare Ti-6Al-4V), and in vitro tests showed higher apatite deposition on as-sprayed coatings and no cytotoxicity, with MG63 osteoblast viability highest on the graded coating.</p>

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Microstructure, Corrosion Resistance, and Bioactivity of Plasma-Sprayed Functionally Graded HA-Al2O3-TiO2 Coatings on Ti Alloy

  • 期刊论文

  • 发表日期：

    2026年5月12日

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  • Kamal Bahadur Yadav,
  • Biraj Kumar Sahoo,
  • Bhagyaraj Jayabalan,
  • Renu Kumari

摘要

Hydroxyapatite (HA) and functionally graded HA-Al2O3-TiO2 coatings were deposited on Ti-6Al-4V alloy via plasma spraying, followed by heat treatment at 750 °C for 2 h. The effects of compositional gradation and heat treatment on microstructure, corrosion behavior, wettability, surface energy, and in vitro bioactivity were systematically evaluated. Both coatings exhibited porous, rough surfaces conducive to osseointegration, with heat treatment reducing roughness (HA: 3.5 to 3.0 µm; graded: 3.9 to 3.54 µm) and porosity (HA: 20 to 17%; graded: 25 to 20%). Corrosion studies showed that the post-heat-treated graded coating had a more noble corrosion potential (Ecorr =  − 0.12 V) and a reduced corrosion rate (2.71 × 10−2mm/year) compared to as-sprayed graded (Ecorr =  − 0.18 V, corrosion rate − 3.60 × 10−2 mm/year) and HA coating (Ecorr = -0.25 V, corrosion rate − 4.57 × 10−2 mm/year). Polarization resistance and EIS confirmed superior stability, with post-heat-treated charge transfer resistance versus HA. Improved corrosion resistance is attributed to densification, reduced porosity, and the barrier effect of Al2O3 and TiO2. Wettability improved (contact angles 35-42° vs. 60° for bare Ti-6Al-4V), and in vitro tests showed higher apatite deposition on as-sprayed coatings and no cytotoxicity, with MG63 osteoblast viability highest on the graded coating.