原位合成WC-6Co复合粉末制备超细YG6硬质合金

In-situ Preparation of Ultra-fine YG6 Cemented Carbide via Sintering of WC-6Co Composite Powder

将原位合成WC-6Co复合粉末采用干袋式冷等静压压制成型(压制压力1×108 Pa、保压时间15 s),将压制好的坯料采用低压烧结炉烧结(烧结温度1360℃、烧结时间40 min、加压5 MPa、保温保压时间20 min),烧结制备超细YG6硬质合金,对合金的形貌、金相组织及物理力学性能进行分析。结果表明:原位合成WC-6Co复合粉末制备的超细YG6硬质合金,晶粒异常长大,WC平均晶粒尺寸为0.8μm,硬度HV30为(21500±100)MPa,较传统超细YG6X硬度高。再将WC-6Co复合粉末采用滚动湿磨、压力式喷雾干燥、掺成型剂、挤压成型、低压烧结等工序制备超细YG6硬质合金,研究不同晶粒长大抑制剂配比、球磨时间、挤压压力、烧结温度对合金性能的影响。结果表明:添加0.3%VC、0.8%Cr3C2(质量分数),湿磨48 h,挤压压力24 MPa,烧结温度1340℃,制备的超细YG6硬质合金WC晶粒均匀,无异常长大的WC晶粒,WC平均晶粒度尺寸0.4μm,呈多边形,外形较圆。强度、硬度最高,抗弯强度TRS为(2250±20)MPa、硬度HV30为(22600±100)MPa。断口形貌为沿晶断裂,沿WC与WC晶界断裂或WC与Co晶界断裂。

The in-situ preparation of WC-6 Co composite powder was subjected to dry-bag type cold iso-static pressing without any pre-treatment(The pressing pressure was 1×108 Pa and the holding time was 15 s).Ultra-fine YG6 cemented carbide was prepared by sintering the pressed blank in a low-pressure sintering furnace at a sintering temperature of 1360℃for40 min,and it was kept under 5 MPa pressure holding for 20 min.The morphology,metallography and physical mechanics properties of the YG6 cemented carbide were analyzed.The results show that abnormal grain growth can be observed from the ultra-fine YG6 cemented carbide,and the average grain size of the WC alloy is 0.8μm.The hardness(HV30)is(21500±100)MPa,which is higher than that of the conventional ultra-fine YG6X cemented carbide.Then,the composite powder of WC-6Co was used to produce ultra-fine size YG6 cemented carbide by processes of wet-milling,pressure type spray drying,binder adding,extrusion forming,and low-pressure sintering.The effects of different grain growth inhibitor ratios,ball-milling time,extrusion pressure and sintering temperature on the properties of the alloy were investigated.The results show that when 0.3 wt%VC and 0.8 wt%Cr3C2 are added,wet milling time is 48 h,extrusion is at 24 MPa pressure and sintering temperature is 1340℃,the produced ultra-fine YG6 cemented carbide has homogeneous WC grain size,and no WC grains with abnormal growth can be observed from the OM image of the YG6 cemented carbide.The average grain size of WC alloy is 0.4μm,and the grains are in polygonal shapes with relatively round outlines.The strength and hardness of YG6 cemented carbide prepared under these conditions are the highest.The TRS of YG6 cemented carbide is(2250±20)MPa,and the hardness(HV30)is(22600±100)MPa.Intergranular fracture,along the WC and WC grain boundary fracture or WC and Co grain boundary fracture can be observed from the morphology of fractures.