钛及钛合金表面金属电沉积的预处理问题

分别采用大气等离子喷涂APS和带延长Laval喷嘴的大气等离子喷涂制备了Al2O3-3%TiO2涂层,对涂层的相组成、显微结构、结合强度、显微硬度等进行了评价,并和常规大气等离子喷涂氧化铝涂层的性能进行了对比,根据粒子在焰流中的特征对涂层性能差异进行了讨论。结果表明,两种Al2O3-3%TiO2涂层均以γ-Al2O3为主,其中还含有少量的α-Al2O3和微晶或非晶。带Laval喷嘴APS所制备涂层的孔隙率、显微硬度和结合强度均明显劣于普通APS涂层,但前者涂层的沉积率达到70%,明显高于后者,大大降低了涂层的生成成本。粒子特征分析表明,延长的Laval喷嘴降低了粒子在等离子焰流中的速度,延长了粒子在焰流中的停留时间,从而使涂层的结合强度和致密度降低,而使涂层沉积率有明显升高。

Pretreatment on Electrodepositing of Titanium and Titanium Alloys

Al_2O_3-3 % TiO_2 coatings were prepared by conventional air plasma spray (APS) and air plasma spray with extended Laval nozzle in this paper. The phase composition, microstructure, adhesive strength and micro-hardness for the two techniques were characterized respectively by comparing with those of conventional APS Al_2O_3 coating. The significant difference between two Al_2O_3-3 % TiO_2 coatings was investigated according to in-flight characteristic in plasma plume. The results showed that both of Al_2O_3-3 % TiO_2 coatings were mainly composed of γ-Al_2O_3, and a small fraction of α-Al_2O_3 and fine crystal or noncrystal were also found in the coatings. APS with extended nozzle sprayed coatings exhibited worse properties in porosity, microhardness and adhesive strength than conventional APS, but the deposition efficiency for the former was obviously higher than the latter, which reached 70 % and greatly lowered the cost of coating production. Particle characteristic revealed that extension of nozzle decreased the in-flight velocity and prolonged the duration in plasma plume, which resulted in the decrease of adhesive strength and density and the increase of deposition efficiency.