Surface quality of cemented tungsten carbide finished by direct cutting using diamond-coated carbide end mill

• Published in: Journal of manufacturing processes Vol. 61; pp. 83 - 99
• Main Authors: Okada, Masato, Shinya, Masayoshi, Kondo, Atsuyuki, Watanabe, Hidehito, Sasaki, Toshihiko, Miura, Takuya, Otsu, Masaaki
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2021
• Subjects: Diamond-coated carbide end mill; Residual stress; Surface quality; Transverse rupture strength; Tungsten carbide; Transverse rupture strength; Diamond-coated carbide end mill; Tungsten carbide; Surface quality; Residual stress
• ISSN: 1526-6125; 2212-4616
• DOI: 10.1016/j.jmapro.2020.11.004

•Superiority of direct cutting of cemented carbide with diamond-coated tool was shown.•Surface quality in direct cutting, electrical machining, and polishing was compared.•Specularity of finished surface similar to polishing was obtained via direct cutting.•Large compressive residual stress can also be obtained via direct cutting.•Higher transverse rupture strength can be achieved compared with polishing. This study addresses the finished surface quality of cemented tungsten carbide obtained via direct cutting with a diamond-coated carbide end mill under ultrasmall feed rates. The surface appearance, composition distribution, profile, roughness, residual stress, and transverse rupture strength were experimentally investigated. The finished surfaces obtained via electric discharge machining with two types of machining conditions and mechanical polishing processes were also evaluated to compare the surface quality. Two types of cemented tungsten carbide materials, TAS VC-70 and VM-40, were applied as the workpiece materials. A mirror surface can be obtained via direct cutting and mechanical polishing with both materials. The microstructure morphologies of the finished surface obtained via direct cutting were different from those obtained via mechanical polishing. In the case of VC-70 which has larger tungsten carbide grain size and higher cobalt content, the flat cross-section of the tungsten carbide grain under ductile mode cutting was conspicuous in direct cutting under small feed rate and depth of cut. In contrast, an extremely thin layer composed of fine grains of tungsten carbide and cobalt was observed on the finished surface in direct cutting under comparatively large feed rate and depth of cut. The surface roughness and profile of the finished surface resulting from direct cutting were comparatively rougher than those resulting from mechanical polishing, although the finished surface was significantly smoother than that resulting from electric discharge machining. The residual stress of the subsurface obtained via direct cutting showed larger compressive stress than that obtained via electric discharge machining and mechanical polishing under all cutting conditions and materials. Moreover, satisfactory transverse rupture strength can be obtained via direct cutting in both materials compared with other processes, and two times more transverse rupture strength can be achieved via direct cutting compared with the case of electric discharge machining in VM-40 cutting.