| Bio-coatings,especially the biological active coatings, bear the effects of loading and body fluid. They are prone to damaging and fracturing, and further inflict great pain on human body. Up to now there are only several papers on it. In this study, wollastonite coatings, used as an example of bio-coatings will be deposited on Ti alloys substrate by plasma spraying method. The stress field are introduced by indentation test and the coating coupon be soaked in SBF (Simulated body fluid) solution. The effect of loading position on the microstructure of indentation is studied. The stress state is also described through using Raman spectroscopy and Finite Element Method (FEM).The experimental results show that:(1) Cracks can be caused by the indentation along the corner of the indentation. The cracks are longer when the indentations locate the position close to the coating surface, compared with those close to the substrate along the direction parallel to the spraying direction under the same loading. When the coatings are socked in SBF solution, cracks propagate firstly and then the length maintain unchangeable. The cracks close to the coating surface need shorter time to transfer to the unchanging condition.(2) The indentation is smaller when it locates in the middle of the coupon compared with those on the sides along the direction perpendicular to the spraying direction. In addition, the length of cracks on the sides of the coupon needs longer duration to become unchangeable.(3) Results of Raman spectroscopy show the stress in coatings.(4) The stress obtained by FEM can explain the coating behavior in SBF. |
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