Research On Preparation And Property Of Wear Resistance Ceramic Coating On Titanium Alloy With Micro-arc Oxidation Technology

ABSTRACT:Titanium Alloy is widely used as high-strength lightweight material, but its weakness of low surface hardness and pool wear resistance limited its usage. Micro-arc oxidation is one of the surface processing methods which can improve titanium alloy's wear resistance. Nowadays, the study on titanium wear resistance coating prepared by MAO technology was carrying out gradually. The electrolyte with addition of sodium aluminate and sodium phosphate is the first choice through most studies. However, few studies were developed on the optimization of preparing MAO coating and its wear resistance.Several MAO wear resistance coatings were prepared under different parameters, including solution formula, voltage, frequency and processing time, in this paper. The affect patterns of these parameters were also studied. By taking friction and wearing test, the wearing resistance principles of the ceramic coatings were further studied.The results show that changing of the solution formula will obviously change the surface roughness, the abrasion rate and the average friction coefficient of MAO coatings. Further analysis show that sodium phosphate is the key factor to affect the surface roughness but sodium aluminate affect more on the abrasion rate and the average friction coefficient. The ideal solution is 5g/L sodium phosphate and lOg/L sodium aluminate.The surface roughness, the abrasion rate and the average friction coefficient of MAO coatings were changed sharply as the value of voltage, frequency or processing time was different. Filled in orthogonal arrays, the results show that the key factor is positive voltage to surface roughness, negative voltage to abrasion rate, and processing time to average friction coefficient. Recommend parameters were given and tested for different situations.The ceramic coatings were mainly composed byα-Al2O3, rutile TiO2, anatase TiO2 and Al2TiO5, and these hard components played important role in the improvement of titanium surface performance. The ceramic coating is much harder than the substrate, and harder than GCr15. This is good for the reduction of abrasion rate. Generally speaking, the less the surface roughness is, the less average friction coefficient will be.The wear mechanisms of titanium substrate are mainly abrasive wear and adhesive wear. The wear mechanism of ceramic coating is abrasive wear. The high hardness ceramic coating protects the titanium substrate very well.