Synthesis of RF Plasma-sprayed Coatings Based on the Controls of Droplet Flattening, Solidification and Reaction Step

基于熔滴压平、凝固和反应步骤控制的射频等离子喷涂涂层的合成

基本信息

批准号：
09450280
负责人：
TSUNEKAWA Yoshiki
金额：
$ 8.7万
依托单位：
Toyota Technological Institute
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1999
项目状态：
已结题

项目摘要

This research has been performed to understand the fundamental phenomenon in the synthesis of metal and intermetallic matrix composite coatings by reactive RF plasma spraying with premixed elemental powder, which is based on the droplet flattening, solidification and reaction with gases.Typical splat morphology of impinged titanium droplets on a substrate is a disk-type with an outer peripheral fringe. If the supplied titanium powder size becomes finer or the nitrogen partial pressure, splats containing prominent asperities (TiN) with a smaller flattening ratio appear along with the plain disk-type. Aluminum splats are also classified into two categories : a disk-type with an irregular outer periphery and a semi-nodular-type. Oxygen exists on the splat surfaces, on which there are nitrogen concentrated areas corresponding to AIN. Consequently, the nitride formation proceeds on titanium and aluminum droplets during the flight as well as on the substrate. If the substrate temperature in … More higher than 873 K just before spraying with premixed titanium and aluminum powder, the formation of TiAl and TiィイD22ィエD2SIN proceeds on the substrate.In situ composite coatings containing titanium carbide (TiC) precipitates were synthesized by reactive RF plasma spraying with elemental titanium powder, in which the effect of methane concentration premixed into the plasma gas on the TiC formation was examined through the process. The absorption of decomposed carbon into molten titanium droplets occurs during their flight in the plasma flame, so that fine TiC precipitates which increase in volume with mixed methane are recognized in the sprayed titanium particles. The flattering ratio of splats impinged on a substrate decreases with increasing premixed methane. The amount of TiC precipitates in titanium matrix coatings is approximately five times higher than that in sprayed particles during their flight regardless of premixed methane. Hence, the TiC formation is dominated at the splat depositing step, because the time exposed by the methane mixed plasma flame is much longer than the flight time of droplets. The maximum volume fraction of TiC precipitates is approximately 30 vol% in the coatings. Less

本研究旨在了解采用预混合元素粉末进行反应性射频等离子喷涂合成金属和金属间基复合涂层的基本现象，该涂层基于液滴压平、凝固以及与气体的反应。受阻钛的典型溅镀形态基材上的液滴呈圆盘状，具有外周边缘。如果供给的钛粉尺寸变细或氮分压变大，则液滴会含有显着的凹凸。与平坦的圆盘型一起出现的扁平率较小的(TiN)铝板也分为两类：外周不规则的圆盘型和板表面上存在的半球状型。其上有与 AIN 相对应的氮集中区域，如果基材温度高于 873，则在飞行过程中钛和铝液滴上会形成氮化物。在喷涂预混钛粉和铝粉之前，在基体上形成 TiAl 和 TiD2SIN。采用反应性射频等离子喷涂元素钛粉，合成了含有碳化钛 (TiC) 沉淀的原位复合涂层，其中通过该过程检查了预混入等离子气体中的甲烷浓度对 TiC 形成的影响。液滴在等离子火焰中飞行时发生，因此在喷射的钛颗粒中可以看到随着混合甲烷而体积增加的细小TiC沉淀物，随着预混合甲烷沉淀物的量的增加，撞击到基材上的碎片的扁平率降低。无论预混合甲烷如何，钛基体涂层中的颗粒物在飞行过程中大约比喷射颗粒高五倍。因此，TiC 的形成主要在溅射处。由于甲烷混合等离子体火焰暴露的时间远长于液滴的飞行时间，涂层中TiC沉淀的最大体积分数约为30 vol%。