BT20钛合金表面电火花沉积WC涂层微观组织研究

Microstructure of Electro-Spark Deposition WC Coating on BT20 Titanium Alloy

摘要:

以WC为电极，氩气为保护气，采用电火花沉积方法在BT20钛合金基体上制备了强化沉积层。利用SEM、EDS和XRD分析了沉积层的微观结构和物相, 利用显微硬度计测试了沉积层截面的显微硬度。结果表明，沉积层主要由TiC、WC、W和W2C相组成，TiC是电极材料与基体材料反应形成新相，是沉积层的主要组成相；沉积层与基体结合致密，形成良好的冶金结合。沉积层表面呈“泼溅状”形貌，截面组织形貌中观察到纳米级微晶堆垛结构和少量的树枝晶，反映了电火花沉积过程的快速加热和冷凝机制。沉积层显微硬度呈梯度变化，涂层最大硬度是基体的3倍。

Abstract:

The WC coating was produced on the surface of BT20 titanium alloy in Ar atmosphere by electro-spark deposition technique using WC as electrode. The microstructures and the phase compositions of WC coatings were characterized by SEM，EDS and XRD. The microhardness distribution of the deposition coating was studied by microhardness tester. The results show that the coating consists of TiC, WC, W and W2C phases. TiC is a new phase formed by the reaction between the electrode material and the substrate which is the main phase of the deposited layer. The excellent metallurgical bonding between the coating and the substrate is obtained. The coating surface displays a "splash" shape. The nanometer crystallite stacking structure and a small amount of dendritic structure can be observed in the cross section morphology which reflects the electric spark deposition process for rapid heating and the cooling mechanism. The maximum microhardness of the coating is three times of that of the substrate.