Elucidation of Elemental Steps of Thermal Spraying Accompanied by In-Process Reaction and Structure Control in Composite Coatings

阐明复合涂层中伴随过程反应和结构控制的热喷涂基本步骤

• 批准号: 12450306
• 负责人: TSUNEKAWA Yoshiki
• 金额: $ 9.54万
• 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: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12450306/
• 关键词: In-process reaction; HVOF spraying; Plasma spraying; Exothermic reaction; Wettability; In-situ composite; Molten droplet temperature; Flight velocity; 生成複合皮膜; 基材予熱

It is known that thermodynamically unstable hard particles such as WC in composite spray materials are ready to decompose to W_2C and tungsten during the thermal spray process. Reactive thermal spraying based on in-process reactions has been recently focused on the fabrication of composite coatings containing nitrides or carbides as a reinforcement. The present study is classified into two main categories:(1) Fundamental aspects of a plasma sprayed cast iron coating on an aluminum alloy substrate, including (i) the effects of preheat substrate temperature on the splat morphology, (ii) the formation of a reaction layer and pores and (iii) the splat microstructure, were investigated in low pressure plasma spraying. With an increasing substrate temperature, the splat morphology changes from a splash-type to a disk and star-shape. Deformed substrate ridges, mainly due to the slight surface melting, are recognized adjacent to the splat periphery at high substrate temperatures. The flattenin … More g ratio of disk splats decreases with substrate temperature because the ridges act as an obstacle for splat expansion. A reaction layer composed of iron, aluminum and oxygen is ready to form at high substrate temperatures, which, along with the deformed ridges, improves the adhesive strength of splats. However, the pores appear at the splat interface at low substrate temperatures, which hinder the formation of a reaction layer. The amount of graphitized carbon increases in cast iron splats with an increase in substrate temperature.(2) reactive HVOF spraying characterized by high flame velocity and low flame temperature was applied to the formation of in situ composite coatings. Granulated particles of SiO_2/Al-Mg were sprayed onto an aluminum substrate to fabricate the composite coatings. Through the reduction of SiO_2 accompanied by an exothermic reaction, the composite coatings are expected to consist of MgAl_2O_4 and Al-Si alloy matrix. However, the sprayed coatings actually consist of MgAl_2O_4, Al-Si and additional Mg_2Si. This is because the formation rate of Mg_2Si is much faster compared with that of MgAl_2O_4, although MgAl_2O_4 is more thermodynamically stable than Mg_2Si. The amount of formed MgAl_2O_4 decreases with an increase in the spraying distance, although it gives a longer in-flight period of droplets. Hence, the in-process reaction such as MgAl_2O_4 formation mainly occurs on a substrate. Less

众所周知，在热喷雾剂过程中，热力学不稳定的硬颗粒（例如复合喷雾材料中的WC）可以分解为W_2C和Tungsten。基于过程中反应的反应性热喷涂最近已集中在含有硝酸盐或碳化物的复合涂料的结构上。本研究分为两个主要类别：（1）等离子体在铝合金底物上喷涂铸铁涂层的基本方面，包括（i）预热底物温度对SPLAT形态的影响，（ii）反应层和孔的形成，孔和（iii）Splat Microstructure在低压力中调查了Splat Microstructure。随着底物温度的升高，SPLAT形态从飞溅型变为磁盘和星形。变形的底物脊，主要是由于略有表面熔化，在高基质温度下被识别为SPLAT外周的邻近。扁平蛋白…更多的磁盘夹夹的比率随底物温度降低，因为脊充当了Splat膨胀的障碍。由铁，铝和氧气组成的反应层准备在高底物温度下形成，该温度与变形的脊一起改善了碎屑的粘附强度。然而，孔出现在SPLAT界面处的低底物温度，这阻碍了反应层的形成。随着底物温度的升高，铸铁夹的石墨化碳的数量增加。（2）以高火速度和低火焰温度为特征的反应性HVOF喷雾剂在原位复合涂料的形成中施加。将SIO_2/Al-Mg的颗粒颗粒喷涂到铝基板上以制造复合涂料。通过减少通过放热反应完成的SIO_2，复合涂料预计由MGAL_2O_4和AL-SI合金矩阵组成。但是，喷涂的涂料实际上由MGAL_2O_4，Al-SI和其他MG_2SI组成。这是因为MG_2SI的形成速率与MGAL_2O_4的形成速率要快得多，尽管MGAL_2O_4比MG_2SI更热情地稳定。尽管它给出更长的液滴时期，但形成的MGAL_2O_4的量随着喷雾距离的增加而减小。因此，诸如MGAL_2O_4形成之类的过程中反应主要发生在基板上。较少的