热处理温度对Al_2O_3-TiO_2-MgO等离子喷涂层微观结构和硬度的影响

Effect of Heat-Treatment Temperature on Microstructure and Hardness of Plasma-Sprayed Al_2O_3-TiO_2-MgO Coatings

为了克服Q235碳钢表面等离子喷涂陶瓷层存在的一些缺陷,先在其表面电弧喷涂Ni-5Al粘结层,再大气等离子喷涂Al_2O_3-TiO_2-MgO陶瓷层。利用扫描电镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)研究了氩气气氛中800,900,1 000℃热处理温度对陶瓷涂层断面微观形貌、物相组成的影响;利用HMV-2T型显微硬度计测试其显微硬度。结果表明:经过热处理,Al_2O_3-TiO_2-MgO陶瓷涂层中的氧化铝和氧化钛组织相互扩散,组织界面模糊,同时Ni-5Al粘结层与陶瓷涂层与基体也出现了互扩散的现象,形成了扩散层;热处理温度越高,互扩散现象越明显;热处理过程中,陶瓷涂层中扁平状结构演化为相互钉扎,促进了Al_2O_3陶瓷涂层硬度的提高。

The carbon steel surface was pre-treated by arc spraying for preparing Ni-5Al bonding layer and then treated by atmospheric plasma spraying for synthesizing Al2O3-TiO2-MgO ceramic coating. The effects of heat-treatment temperature( 800,900,1 000 ℃) on the morphology of fracture surface and the composition of the ceramic coatings were analyzed by scanning electron microscopy( SEM) with electron probe X-ray microanalysis( EPMA) and X-ray diffractometer( XRD). Moreover,the mechanical properties of the coatings were tested by a Vickers hardness test. Results revealed that the alumina phase and titanium oxide phase interfacial diffused to each other in Al2O3-TiO2-MgO ceramic coating after heat treatment,and their interface became blurry. Besides,similar inter-diffusion phenomenon was observed on the interface of ceramic coating,Ni-5Al binding layer and the steel substrate,which led to the formation of diffusion layers. With the increase of treatment temperature,the inter-diffusion phenomenon turned out to be more obvious. During treatment process,the lamellar structure in ceramic coating changed into inter-pinning structure,which could enhance the hardness of Al2O3-TiO2-MgO ceramic coating.