INFLUENCE OF DEPOSITION PARAMETERS ON THE POROSITY AND ADHERENCE OF COATINGS SPRAYED BY COMBUSTION FLAME FROM 31SiO2-11P2O5-51-CaO-7MgO BIOGLASSES

Abstract

It was studied the influence of both: the flame enthalpy and spray distance on the adhesion, the surface roughness, the porosity and the micro hardness of coatings elaborated by flame spraying from bioactive glass powders of the system 31SiO2-11P2O5- 51CaO-7MgO. Two acetylene-oxygen volumetric ratios: 1:1,5 and 1:2 were used to produce the flame; the distribution size particles of powders sprayed was between 45 and 75 µm; the spray distances were 8 and 10 cm and AISI 316L steel was used as substrate. The coatings obtained using the 1:2 gas ratio showed both better physical and mechanical properties than those obtained by the 1:1,5 gas ratio due to their more homogeneous structure. Regarding to the spray distance, two opposite effects were detected: when a 1:1,5 C2H2:O2 gas ratio was used, the temperature of melted particles was excessive producing splashing during the impact of these particles on the substrate and then the structure obtained in the coatings was more irregular and porous, while, using a 1:2 gas ratio the particles reached the substrate surface at an adequate temperature to produce a more homogeneous structure and a higher crystallization.