| 초록 |
New method of welding process is Friction Stir Welding method (FSW) that gets the limelight. FSW was developed in 1991 and is successfully being applied to an increasing number of joining applications worldwide. The FSW advantages of this solid-state joining process, which uses frictional heat generated by a rotating and traversing cylindrical tool with a profiled pin along a square butt weld joint, encompass better mechanical properties, low residual stress and deformation, weight-savings, and reduced occurrence of defects, compared to the conventional welding methods. Recently, research on the FSW process has mainly focused on the joining of low-melting metallic materials, such as aluminum alloys with steel. Tungsten carbide-cobalt hard materials (WC-Co) are widely used for a variety of application such as welding tool, machining, cutting and drilling. Morphologically, they consist of a high volume fraction of the “hard” hexagonal WC phase embedded within a soft and tough Co binder phase. An increase in the density of WC-10wt.%Co was not accomplished by conventional sintering method. The demonstrated advantages of sps processes are rapidly densification to near theoretical density in a relatively short time and without significant change in a grain size. The microstructure of WC-10wt% Co composite prepared by ball milling was investigated by X-ray diffraction, Field Emission Scanning Electron Microscopy and Grain size analysis. The sintering behavior of WC-Co powder and mechanical properties of its sintered body were investigated in this study. Grain sizes of WC after sintering was 736 nm under 60 MPa at 1200℃. Also, it was found that the Vickers hardness and fracture toughness of WC-Co sintered body were 2068.38 kg/mm2 and 10.21 MPa.m½, respectively. |
