Spatial and depth-resolved studies of air plasma-sprayed hydroxyapatite coatings by means of diffraction techniques: Part I

SURFACE & COATINGS TECHNOLOGY

卷:294

Article

Ntsoane, Tshepo P.^1,5  Topic, Mira²  Haerting, Margit³  Heimann, Robert B.⁴  Theron, Chris⁵ 

[1] NECSA Ltd, Div Res & Dev, POB 582, ZA-0001 Pretoria, Gauteng, South Africa

[2] Nat Res Fdn, iThemba LABS, Mat Res Dept, POB 722, ZA-7129 Cape Town, Western Cape, South Africa

[3] Univ Cape Town, Dept Phys, ZA-7701 Cape Town, South Africa

[4] Stadtpk 2A, D-02826 Gorlitz, Germany

[5] Univ Pretoria, Dept Phys, Lynnwood Rd, ZA-0002 Pretoria, South Africa

关键词: Plasma-sprayed hydroxyapatite coatings;    X-ray diffraction;    Quantitative phase analysis;    Degree of crystallinity;    Residual stress;   

DOI  :  10.1016/j.surfcoat.2016.03.045

来源: Elsevier

【 摘 要 】

Hydroxyapatite coatings (HAp, Ca-10(PO4)(6)OH2) were deposited by air plasma spraying onto Ti6Al4V substrates and investigated to determine the depth-dependent behaviour of phase composition, crystallinity, and residual stress using diffractometric techniques. Through-thickness characterisation was carried out by conventional X-ray and synchrotron radiations in reflection and transmission geometries. Results showed HAp together with its thermal decomposition products, tetracalcium phosphate (TTCP), tricalcium phosphate (TCP) and calcium oxide to be present throughout the coating thickness. Quantitative phase identification employing Rietveld refinement showed HAp and TTCP to be the two major phases, with the former decreasing with depth whilst the latter increases. The largest changes were observed adjacent to the coating-substrate interface region. Crystallinity investigation showed a similar trend, revealing a more crystalline near-surface region and increasing amorphisation toward the coating-substrate interface. Residual stress investigation revealed the normal components sigma(11) and sigma(33) to be tensile and compressive, respectively. The stresses relax and increase to respective minimum and maximum within the first 145 mu m. With further penetration depth, both normal stress components became tensile. (C) 2016 Elsevier B.V. All rights reserved.

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