소결온도 변화에 따른 Binderless-WC 소결체 특성평가

In this study, Binderless-WC hard materials were fabricated using the pulsed current activated sintering (PCAS) process for a Friction Stir Welding tool and difficult-to-cut tool application. Tungsten carbide (WC) hard materials are used in various industries and possess a superior hardness compared to other hard materials. They have particularly high melting points, high strength, and abrasion resistance. 100 mm diameter and 5 mm thick binderless-WC hard materials were fabricated using a 30,000 A pulsed current activated sintering machine and 0.3 to 0.5 μm size WC powders. Variation of properties in binderless WC hard materials by sintering temperature were increased slightly for 0.11 to 0.37 um with a grain size and densified completely for 70.0 to 99.5% for a relative density. Consequently, these materials were almost completely dense with a relative density of up to 99.5% after simultaneous application of 60 MPa pressure and an electric current for 2 min at 1600 oC, almost without any significant change in the crystallite size. The average WC crystallite size that was produced through PCAS was 0.37 μm at 1,600 °C. In terms of mechanical properties, considering only the densified sintered body that the hardness and fracture toughness of binderless-WC hard materials were about 2,661.5 kg/mm2 and 3.90 MPa·m1/2, respectively. (Received December 14, 2018; Accepted March 27, 2019)