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

The microstructural control of tool steel (SKD11) by laser melting and friction stir processing (FSP) was studied. A nanometer-sized microstructure consisting of fine M7C3 carbide (particle size: ∼100 nm) and a matrix (grain size: ∼200 nm) was successfully fabricated by the FSP on the laser treated SKD11. The nanostructured SKD11 had an extremely high hardness of about 900 HV even with its relatively high amount of retained austenite.