Dual-gradient bainite steel matrix composite fabricated by direct laser deposition

Abstract A dual-gradient bainite steel matrix composite was fabricated by direct laser deposition (DLD) method. The decomposition of WC (reinforcements) during DLD is utilized to adjust the gradient microstructure of the composite. Both the matrix morphology and the reinforcement distribution present obvious gradient variation along the deposition direction. The microhardness and impact toughness exhibit the opposite tendency from the bottom to top of the composite, which shows a good agreement with the gradient microstructure. The surface microhardness and impact toughness of the dual-gradient composite are 510 HV and 75 J/cm 2 , respectively. The hardness and toughness combination of the composite is superior to most steels for railway frog. The dual-gradient composite has great potential in improving the performance of railway frog.