Experimental Characterization of a Direct Metal Deposited Cobalt-Based Alloy on Tool Steel for Component Repair

Abstract

Casting dies made of tool steel are subject to impact, abrasion, and cyclic thermo-mechanical loading that can result in damage such as wear, corrosion, and cracking. To repair these defects, materials enveloping the defects need to be machined off and then refilled. In this study, V-shaped defects with varied sidewall inclination angles were prepared on H13 tool steel substrates and refilled with a cobalt-based alloy using direct metal deposition process (DMD) for superior hardness and wear resistance. The microstructure of rebuilt samples was characterized using an optical microscope (OM) and scanning electron microscope (SEM). Elemental distribution from the substrate to deposits was analyzed using energy-dispersive spectrometry (EDS). The mechanical properties of repaired samples were evaluated by tensile testing and microhardness measurement. A fracture mechanism in tensile testing was analyzed by observing the fracture surface. The experimental result reveals that V-shaped defects with sidewall beyond certain angles can be successfully remanufactured. The deposits were fully dense and free of defects. The microstructure and tensile testing confirm the solid bonding along the interface. The tensile testing shows the average ultimate tensile strength (UTS) of the repaired samples is approximately 620 MPa, where samples fractured at the deposits region. The hardness measurement reveals the hardness of deposits is around 800 HV, which is much higher than the hardness of the substrate.