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

摘要:

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1000bar、保压时间15s），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40min，加压5MPa，保温保压时间20min），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平均晶粒度为0.8μm，硬度HV30为2150±10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，通过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0.3wt%VC、0.8wt%Cr3C2，湿磨48h，挤压压力24MPa，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平均晶粒度为0.4μm，呈多边形，外形较圆。强度、硬度最高，TRS为2250±20MPa、HV30为2260±10。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。

Abstract:

The in-situ Preparation of WC-6Co composite powder was subjected to dry-bag type cold iso-static pressing without any pre-treatment (The pressing pressure was 1000 bar 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 ℃ with 40 min sintering time, and it was kept under 5 MPa pressure holding for 20 min). To analysis the morphology, metallography and physical mechanics properties of the YG6 cemented carbide, The results showed that: abnormal grain growth can be observed from the Ultra-fine YG6 cemented carbide, the average grain size of the WC alloy is 0.8 μm; The hardness HV30 is 2150±10, which is higher than the conventional Ultra-fine YG6X cemented carbide. Then, the composite powder of WC-6Co was produced to ultra-fine size YG6 cemented carbide through processes of wet-milling, pressure type spray drying, binder adding, extrusion forming, low-pressure sintering. Through the analysis of the effects of different grain growth inhibitor ratios, ball-milling time, extrusion pressure and sintering temperature on the properties of the alloy were investigated by testing the mechanical to the physical properties of the carbide, the results showed that: when 0.3 wt % VC and 0.8 wt % Cr3C2 were added, wet milling 48h , extrusion at 24 MPa pressure and sintering temperature of 1340 ℃, the produced Ultra-fine YG6 cemented carbide has homogenous WC grain size, No WC grains with abnormal growth can be observed from the Metallographic diagram of the YG6 cemented carbide. The average grain size of WC alloy is 0.4 μm, 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 HV30 is 2260±10. 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.