Preparation Of Fe-based Amorphous Coatings By High Velocity Oxygen-fuel Spraying And Its Application As Bone Implant Materials

Biodegradable magnesium alloys are expected to be a new generation of bone implant materials due to their unique properties.However,the problem of rapid corrosion rate in living organisms severely limits their clinical applications.In this study,an Fe78Si9B13 amorphous coating was deposited on the surface of ZK60A magnesium alloy by high velocity oxygen-fuel(HVOF)spraying technique to improve the corrosion resistance of the alloy.Firstly,four groups of increasing combustion ratio parameters were used to prepare Fe-based amorphous coatings on the surface of magnesium alloy.The microstructure and mechanical properties of the coatings were characterized,and the effects of combustion ratio on the HVOF sprayed amorphous coatings were analyzed.Secondly,the corrosion behavior of the amorphous coating in simulated body fluid(SBF)was studied by immersion corrosion test,electrochemical potentiometric polarization test,and impedance spectroscopy test.The bone bioactivity of the coating was studied by analyzing the surface products of immersion corrosion.Finally,the amorphous coating was subjected to heat treatment at different temperatures and times,the influence of heat treatment on the coating structure and performance was studied.By characterizing and analyzing the Fe-based amorphous coatings prepared under different combustion ratio parameters,it was found that the hardness and amorphous content of the coatings initially increased and then decreased as the combustion ratio increased.The coating H3 prepared at the combustion ratio of 1.19 had the highest hardness and amorphous content.The porosity of the coating decreased as the combustion ratio increased,and the coating prepared at the maximum combustion ratio had the highest oxide content.The degradation rate(0.12 mm/a)of coating H3 in SBF was much lower than that of the magnesium alloy(6.48 mm/a),and this degradation rate met the requirements for implant degradation rate at the early stage of bone healing.The immersion corrosion test in SBF showed that the Fe-based amorphous coating had good bone bioactivity.By characterizing the Fe-based amorphous coatings after heat treatment at different temperature and time,it is found that the amorphous structure of the coatings is almost unchanged after 30 min of heat treatment at the initial temperature of crystallization(450℃),the porosity of the coatings decreases due to structural relaxation,and the corrosion resistance of the coatings in SBF is improved.After 30 min of heat treatment above the initial temperature of crystallization(550℃),the crystal phase of the coating increases and the pores decrease,and the overall structure change makes the corrosion resistance of the coating deteriorate in SBF.After heat treatment at constant temperature(550℃)for 10 min,30 min and 60 min,the content of amorphous phase in the coating gradually decreased with the extension of heat treatment time,and the coating was completely crystallized when the heat treatment time reached 60 min.With the increase of crystal phase,the porosity of the coating gradually decreases,the hardness of the coating decreases,and the corrosion resistance of the coating in SBF gradually deteriorates.The corrosion rate of the original spray coating gradually increases from 0.12mm/a to 0.84mm/a.