Flame Spray Projection of a Bioactive Hidroxyapatite Coating on Ti6Al4V for Biomedical Applications

Abstract

This work consisted in the development and characterization of a bioactive coating on Ti6Al4V samples by flame spray projection. A synthetichidroxyapatite powder was used to form the coatings. Oxygen and acetylene gas were used as combustible, and the metallic substrate was Ti6Al4V with a roughness of 0.4 and 2.3 μm. The time process varied from 5 to 60 seconds. The projection distance was of 22 cm.The spray coatings were mechanical tested; in all cases, the results indicated that the coatings were well adhered to the metallic surfaces and the metallic subtracts did not present any degradation of the mechanical properties. In addition, the coatings were immersed in simulated body fluids for 21 days in physiological conditions to evaluate the bioactivity. The results demonstrated that the coatings are potentially bioactive through the formation of a dense and homogeneous apatite layer similar to the bone. Results of X-ray diffraction exhibited evidence of a hidroxyapatite layer and by energy dispersive spectroscopy, a Ca/P ratio of 1.57 was obtained. This is an indication of that the use of flame spray projection to coat Ti6Al4V substrates do not decompose the original hidroxyapatite powder. Compositional analysis of the remnant fluids, made by inductively coupled plasma spectrometry, showed that nonmetallic ions were present in the coatings.