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首页> 外文期刊>Biomaterials >Plasma-sprayed hydroxyapatite (HA) coatings with flame-spheroidized feedstock: microstructure and mechanical properties.
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Plasma-sprayed hydroxyapatite (HA) coatings with flame-spheroidized feedstock: microstructure and mechanical properties.

机译：等离子喷涂的羟基磷灰石（HA）涂层与火焰球化的原料：微观结构和力学性能。

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摘要

Flame-spheroidized feedstock, with excellent known heat transfer and consistent melting capabilities, were used to produce hydroxyapatite (HA) coatings via plasma spraying. The characteristics and inherent mechanical properties of the coatings have been investigated and were found to have direct and impacting relationship with the feedstock characteristics, processing parameters as well as microstructural deformities. Processing parameters such as particle sizes (SHA: 20-45, 45-75 and 75-125 microm) and spray distances (10, 12 and 14 cm) have been systematically varied in the present study. It was found that the increase of particle sizes and spray distances weakened the mechanical properties (microhardness, modulus, fracture toughness and bond strength) and structural stability of the coatings. The presence of inter- and intralamellar thermal microcracks, voids and porosities with limited true contact between lamellae were also found to degrade the mechanical characteristics of the coatings, especially in coatings produced from large-sized HA particles. An effort was made to correlate the effects of microstructural defects with the resultant mechanical properties and structural integrity of the plasma-sprayed hydroxyapatite (HA) coatings. The effects of different heat treatment temperatures (600, 800 and 900 degrees C) on the mechanical properties of the coatings were also studied. It was found that a heat treatment temperature of 800 degrees C does enhance the microhardness and elastic modulus of the coatings significantly (P < 0.05) whereas a further increment in heat treatment temperature to 900 degrees C did not show any discernable improvements (P > 0.1). The elastic response behaviour and fracture toughness of both the as-sprayed and heat-treated HA coatings using Knoop and Vickers indentations at different loadings have been investigated. Results have shown that the mechanical properties of the coatings have improved significantly despite increasing crack density after heat treatment in air. Coatings produced from the spheroidized feedstock of 20-45 microm (SHA 20-45 microm) sprayed at a stand-off distance of 10 cm were found to possess the most favourable mechanical properties.
机译：火焰球化的原料具有出色的已知热传递和稳定的熔化能力，可用于通过等离子喷涂生产羟基磷灰石（HA）涂层。已经对涂层的特性和固有的机械性能进行了研究，发现它们与原料特性，加工参数以及微观结构变形具有直接的影响关系。在本研究中，系统地改变了加工参数，例如粒度（SHA：20-45、45-75和75-125微米）和喷涂距离（10、12和14厘米）。已发现，粒径和喷雾距离的增加削弱了涂层的机械性能（显微硬度，模量，断裂韧性和粘结强度）和结构稳定性。还发现层间和层间热微裂纹，薄层之间真正接触有限的空隙和孔隙的存在降低了涂层的机械性能，特别是在由大尺寸HA颗粒制成的涂层中。努力使微观结构缺陷的影响与等离子喷涂羟基磷灰石（HA）涂层的最终机械性能和结构完整性相关联。还研究了不同的热处理温度（600、800和900摄氏度）对涂层机械性能的影响。发现800摄氏度的热处理温度确实可以显着提高涂层的显微硬度和弹性模量（P <0.05），而将热处理温度进一步提高到900摄氏度则没有任何明显的改善（P> 0.1）。 ）。研究了使用努氏和维氏压痕在不同载荷下喷涂和热处理的HA涂层的弹性响应行为和断裂韧性。结果表明，尽管在空气中热处理后裂纹密度增加，但涂层的机械性能仍得到显着改善。发现以20-45微米（SHA 20-45微米）的球形化原料生产的涂层具有10cm的支撑距离喷涂，该涂层具有最有利的机械性能。

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