原位TiC/金属基激光熔覆涂层的微结构特征

Microstructural Characteristics and Wear Properties of in situ Formed TiC Ceramic Reinforced Metal-matrix Composites Coatings by Laser Cladding

利用激光熔覆制备了原位形成TiC陶瓷颗粒增强金属基复合材料涂层 ,TiC为熔覆时原位形成。颗粒细小弥散 ,具有内晶型及密度梯度分布特征 ;HREM观察表明 ,TiC/基体界面结构具有洁净及微晶过渡特征 ,无界面反应物 ;熔覆组织具有较高的显微硬度及耐磨性。

In situ TiC particle reinforced metal matrix composites (PRMMCs) layers by laser syntheses were realized. The reinforced TiC particles were introduced by an in situ reaction of titanium and graphite during laser clad process, rather than TiC particles being directly added into the laser molten pool. The microstructural characteristics, interaction of ceramic particles with a rapidly moved solid/liquid interface, ceramic/matrix interface and wear properties of layers wear studied by OM, TEM and HREM (EDAX/EELS) et al respectively. It was observed that the in situ TiC particles formed in the layer were ultra\|fine, with particle\|size distribution in a sub\| micrometre range. TiC particles distributed dispersely within grains. There existed a critical rapid solidification speed, which resulted in a transition of ceramic particles from pushing to trapping by advancing solid/liquid interface. Additionally, the volume fraction of TiC possessed density\|gradient distribution from the layer/substrate interface to the layer surface. The maximum of volume fraction of TiC particles is about 38% at the sub\|surface of the layer. Moreover, it was observed by HREM that the in situ generated TiC/matrix interfaces were free from gas absorption, oxidation or other deleterious surface reactions, which lead to a strong matrix\|TiC interface bond. The microhardness of PRMMCs layer gradiently changed too and the highest one was 1250 HV0 2 at the sub\|surface. The wear properties of the layer was significantly enhanced, compared to the subtrate materials.