电冶熔铸WCp/钢基复合材料的组织及断口研究

Investigation on Microstructure and Fracture of WC Particles Reinforced Steel Matrix Composites by Electroslag Melting and Casting

用电冶熔铸法制备了20wt%WC颗粒增强钢基复合材料,进行三点弯曲法破断试验,并观测材料的显微组织及断口形貌,分析热处理工艺对显微组织和断口形貌的影响。结果表明:WC颗粒相基本溶解于钢基体相中,并沿晶界生成Fe3W3C复式碳化物,同时两相实现了冶金结合;断口分析证实此类断口为韧———脆复合断口,其中,部分硬质相颗粒表面出现解理断口。热处理工艺和颗粒本身特征均可影响基体断口形貌和断裂机制。淬火态断口基本为沿晶断裂;低温回火态断口以细韧窝及部分沿晶断口为主要断裂机制;退火态断口为准解理及韧窝复合断口。

Steel matrix composites containing 20wt% WCp were produced by electroslag melting and casting method. The microstructure and fracture surface of three point bending specimens were characterized by using scanning electron microscopy (SEM) and light optical microscopy. Influences of heat treatment on microstructure of the composite and its fractograph were investigated. The results show that WC phase is almost dissolved into steel matrix and compound carbide (Fe3W3C) is formed along the grain boundary of steel matrix which contributes to the metallurgical bonding between steel matrix and the particles. Fracture surface analysis confirms that the fracture belongs to ductile and brittle complex fracture, for which some hard phase display partially cleavage fracture. The heat treatment technology and reinforced particle itself can affect the fractograph and mechanism of fracture. Intergranular fracture prevails for as-quenched samples. Combination of fine dimple and partial intergranular fracture are the predominant characteristics observed for the sample stempered at low temperature. The main fracture mechanism of annealed samples is the quasi-cleavage and dispersed dimples fracture.