热处理对复合电冶熔铸WC颗粒增强钢基复合材料力学性能的影响

Influence of heat treatment on mechanical properties of WC particulates reinforced steel matrix composites by composite electroslag melting and casting

采用复合电冶熔铸工艺制备了以5CrNiMo钢为基体、WC颗粒为增强相的颗粒增强钢基复合材料,通过宏微观硬度试验、三点弯曲试验和冲击韧性试验对比分析并综合评定复合材料和5CrNiMo钢的各项力学性能,同时采用扫描电子显微镜观察断口形貌并判定断裂机理。结果表明：大量WC颗粒增强体分布在较软的钢基体上,提高了复合材料的整体硬度,淬透性和淬硬性也较好,但塑性比5CrNiMo钢稍差。在950℃到1050℃淬火时,复合材料的洛氏硬度达到60-66 HRC,抗弯强度达到1600-1650 MPa,均呈现先上升后下降的波动趋势,而冲击韧度变化不明显。对比基体和中小块WC颗粒聚集区,大块硬质相的显微硬度值变化幅度较小。在锻造退火状态下,复合材料为准解理＋韧窝的复合断裂机理,而在淬火回火态时,则转变为解理断裂机制。

WC particulates reinforced steel matrix composites with WC particles as reinforced body and 5CrNiMo steel as matrix were prepared by composite electroslag melting and casting technology. Mechanical properties of the composite and 5CrNiMo steel were analyzed comparatively and evaluated comprehensively by macro and micro hardness test,three point bending test and impact toughness test.Meanwhile,the fracture morphology was observed by scanning electron microscope and the fracture mechanism was determined. The results show that a large number of WC particles distributes on the soft steel substrate,which improves the overall hardness of the composite. The properties of the quenched and hardened one are also good,but the plasticity is lower than that of the 5CrNiMo steel. When quenched between 950 ℃ and 1050 ℃,the rockwell hardness of the composites reaches 60-66 HRC,and the bending strength reaches 1600-1650 MPa,with a fluctuation of first rising and then falling,while the impact toughness change is not obvious. Comparison between the matrix and accumulation area of moderate or small piece of WC particles shows that the rangeability of the microhardness values for large hard phase is smaller. Under the condition of forging and annealing,the composites show the composite fracture mechanism of quasi-cleavage and dimples.While under the condition of quenching and tempering,it turns to the fracture mechanism of cleavage fracture.