Tadashi Mizuno

Nanostructured tool steel fabricated by combination of laser melting and friction stir processing

Abstract The microstructural control of tool steel (SKD11) by laser melting and friction stir processing (FSP) was studied. A nanometer-sized microstructure consisting of fine M 7 C 3 carbide (particle size: ∼100xa0nm) and a matrix (grain size: ∼200xa0nm) was successfully fabricated by the FSP on the laser treated SKD11. The nanostructured SKD11 had an extremely high hardness of about 900xa0HV even with its relatively high amount of retained austenite.

Effect of friction stir processing on microstructure of laser clad cobalt-based alloy

Abstract (The microstructural refinement of cobalt-based alloy (Stellite No. 6) by laser cladding and friction stir processing (FSP) was studied. A nanometer-sized microstructure consisting of fine carbide (particle size: 100–200 nm) and a grain (grain size: 150–250 nm) was successfully fabricated by the FSP on the laser clad cobalt-based alloy. The nanostructured cobalt-based alloy (Stellite No. 6) had an extremely high hardness of about 750 HV.

Microstructural Evaluation of Friction Stir Processed D2 Tool Steel

Modification of AISI D2 tool steel was conducted by friction stir processing (FSP). Effects of tool rotational speed on microstructural evolution and mechanical properties were investigated. Though coarse primary carbides in the size of 10-50 uf06dm were observed before FSP, fine carbides smaller than 20 uf06dm and martensitic matrix with fine grains were obtained after FSP. High hardness of over 900 HV, higher than the hardness in conventional D2 tool steel, was achieved under the condition of moderate rotational speed.