Influences of Argon Atmosphere on Ceramic Coatings on Ti–6Al–4V Alloy by Micro-Plasma Oxidation in Different Solutions

Compound ceramic coatings were prepared on Ti-6Al-4V allosy by pulsed bi-polar Micro-plasma Oxidation (MPO) in NaAlO2(S1) and Na2SiO3(S2) solution respectively. The coated samples were calcined in argon under 1000 oC. The phase composition,morphology and element content of the ceramic coatings were investigated by XRD, SEM and XRF. After oxidation in argon, The Al2TiO5 of S1 coating surface was decomposed into Al2O3. SiO2 was crystalized in S2 coating with the final proportion of SiO2 to TiO2 on the coating surface is 81:18. The morphology of the ceramic coatings after the calcination was also different. S1 coatings calcined in argon were fine, grains and pores were smaller and were combined tightly with the substrate, on the contrary, S2 coatings calcined in argon cracked on the coating surface and were separated with the substrate. The content of elements in the coatings both changed a little, which may be due to the reaction of the substrate in the oxidation. According to the phase composition and the morphology of the coatings, S1 coatings are better than S2 coatings.