TiC-TiB_2电火花复合强化层组织与耐磨性

Microstructures and Wear Resistance of the TiC-TiB_2 Composite Coating Deposited by Electrical Discharge Hardening

以TiC-TiB2复合材料为电极,采用电火花表面强化技术,在40Cr钢表面制备出TiC-TiB2复合强化层。利用SEM和XRD分析了强化层的微观结构和物相,测试了强化层的硬度和耐磨性,并探讨了其磨损机理。结果表明:强化层物相主要为TiB2、TiC和Fe3C等,非晶组织和组织细化使其衍射峰宽化;强化层的显微硬度分布呈梯度变化,最高硬度值是基体硬度值的4倍多;强化层中的硬质相和较高的显微硬度改变了试样间的磨损机制,强化层的磨损机制为显微切削、划擦和疲劳磨损;强化层的耐磨性比基体提高了约5倍,摩擦系数比基体低0.12～0.17。

TiC-TiB2 composite coating was deposited by electrical discharge hardening onto the surface of 40Cr steel with using TiC and TiB2 composite rod as electrode. The composite coating structure and phase compositions were characterized by SEM and XRD, the hardness and its distribution along coating were measured on micro-hardness machine. Wear resistance of strengthen layer was evaluated on MM-200 wear experiment machine. The microstruc- tures,mechanical property and wear resistance of the TiC-TiB2 composite coating were analyzed, and the wear mechanism of strengthened layer was studied. The results suggest that the major phases of the composite coating are TiB2, TiC and Fe3C, the fine crystalline structure and non-crystalline make the diffracting peak widening. The micro hardness distribution along depth of composite coating is unhomogeneous; the micro hardness value of the composite coating is about 4 times the size of the substrate. The wear mechanism of 40Cr steel is mainly attributed to micro-cutting and adhesive wear, but the wear mechanism of composite coating is mainly attributed to micro-cutting, scratch and fatigue abrasion. The results show that the change of wear mechanism between the samples induces to the hard particles and higher hardness of composite coating. Compared with the substrate,wear resistance of composite coating is 5 times higher, wear coefficient of the coating decreased by 0. 12 to 0. 17 under the same wear environment.