金属型表面莫来石-玻璃复合涂层的制备

Preparation of Mullite-Glass Coating on the Surface of Metal Mold

以Al2O3和SiO2为反应物料,加入低熔点玻璃粉,采用热化学反应在金属型表面制备莫来石-玻璃涂层。考察了涂层制备工艺参数对涂层与金属基体结合强度的影响,并利用XRD、SEM和EDS分析了涂层相组成、截面微观结构及元素分布。结果表明,对反应物料进行球磨混合,可增加涂层与金属基体结合强度;提高反应温度、延长反应时间、增加玻璃粉添加量,涂层与基体结合强度呈现先增加后减小趋势。当Al2O3、SiO2、玻璃粉的质量比为2∶1∶3,在720℃反应2h形成的涂层与基体结合紧密,结合强度达8.95MPa。涂层与基体间主要以化学、扩散的方式结合,涂层主要由3Al2O3·2SiO2、Al2SiO5相、非晶玻璃粉及少量Al2O3、SiO2、Fe3Al、FeAl相等组成。

A kind of mullite-glass coating was prepared on the surface of metal mold by thermo chemical reaction method with Al2O3, SiO2 and fusible glass powder. Influences of the process parameters on the bonding strength between coating and metal matrix were investigated. The phase compositions, microstructure of the coating and element distribution were analyzed by XRD （X-ray diffraction）, SEM （scan- ning electron microscope）, EDS （energy dispersedly spectrometer）, respectively. Experimental results show that reaction materials after ball-milling can improve the bonding strength of coating with sub- strate. The bonding strength of coating with substrate is increased firstly and then decreased with the increase of the reaction time, reaction temperature and the content of fusible glass powder. The coating which formed on the surface of metal substrate at 720 ℃ for 2 h is tightly combined with substrate according to the mass ratio of Al2O3, SiO2 and glass powder with 2 ： 1 ： 3, and the bonding strength reaches up to 8.95 Mpa. The interface bonding of coating and substrate is mainly characterized by chemical and diffusional bonding. The coating is mainly composed of 3Al2O3 · 2SiO2, Al2SiO5, amorphous glass powder and a small amount of Al2O3, Fe3Al, FeAl, SiO2.