激光熔覆原位生成CaTiO_3陶瓷涂层及热力学分析

Study on in-situ formation of CaTiO3 biocoating via laser cladding and its thermodynamic analysis

为了改善钛合金表面生物活性,采用500W脉冲Nd∶YAG激光作为热源,平均粒度约为20μm的Ti粉和CaCO3粉为预涂材料,利用激光熔覆原位自生的方法,在Ti-6Al-4V表面制备CaTiO3陶瓷涂层。通过热力学分析,并结合X射线衍射分析方法,研究了原位自生CaTiO3的反应机理以及主要工艺参量(扫描速率、电流强度)对原位自生CaTiO3陶瓷涂层的影响。热力学计算表明,在激光熔池内,可原位生成以CaTiO3为主的陶瓷涂层。结合X射线衍射及激光共聚焦观察结果可知,在脉冲频率为30Hz、脉宽为1.0ms、离焦量为15mm的条件下,合适的扫描速率约为3mm/s,电流强度为240A。最佳条件下制备的涂层主要成分为CaTiO3以及部分钛的氧化物。结果表明,熔覆层内为枝晶和胞晶组织,分布比较均匀,原位生成的陶瓷涂层与基底形成了良好的冶金结合。

CaTiOz biocoating was in-situ fabricated on Ti-6Al-4V substrate via laser cladding technology to improve the bioactivity of titanium alloy. A pulsed YAG laser with a power of 500W was introduced as the radiation source. A mixture of pure titanium powder（ average particle size 20μm） and CaCO3 powder with a certain weight ratio was preplaced on the substrate as the precursor. The mechanism of in-situ fabrication of CaTiO3 bioeoating was investigated by thermodynamic analysis. The effects of laser technologies such as laser scan speed and electrical current on the phase constituents and the surface morphology of the samples were studied. X-ray diffraction characterization and laser confoeal scanning microscopy investigation showed that the proper parameters for laser cladding were as the following： pulsed frequency 30Hz, pulse width 1.0ms, defocus distance 15mm, laser scanning speed about 3mm/s, and electrical currency 240A. CaTiO3 and part of titanium oxides are the main phases in the coating. Optical microscopy result revealed that the microstructure in the coating was characterized as fine dendrites and cellular structure. A metallurgical bonding between the coating and the substrate was obtained.