Abstract
Cold-work tool steel is considered to be a nonweldable metal due to its high percentage content of carbon and alloy elements. The application of a new process of the semisolid joining of two dissimilar metals is proposed. AISI D2 cold-work tool steel was thixojoined to 304 stainless steel by using a partial remelting method. After thixojoining, microstructural examination including metallographic analysis, energy dispersive spectroscopy (EDS), and Vickers hardness tests was performed. From the results, metallographic analyses along the joint interface between semisolid AISI D2 and stainless steel showed a smooth transition from one to another and neither oxides nor microcracking was observed. Hardness values obtained from the points in the diffusion zone were much higher than those in the 304 stainless steel but lower than those in the AISI D2 tool steel. The study revealed that a new type of nonequilibrium diffusion interfacial structure was constructed at the interface of the two different types of steel. The current work successfully confirmed that avoidance of a dendritic microstructure in the semisolid joined zone and high bonding quality components can be achieved without the need for force or complex equipment when compared to conventional welding processes.
Highlights
Cold-work tool steel has many attractive properties such as high wear resistance, high compressive strength, high hardness after hardening, and good dimension stability during heat treatment
There have been a number of reported studies on using a feedstock material with a thixotropic characteristic to weld by employing different methods such as laser welding and friction stir welding, but problems arise with these methods including porosities, loss of alloying elements, bad geometry, and softening of the heat-affected zone resulting in a nonhomogenous microstructure in the heat-affected zone caused by the remelting temperature [1,2,3]
A new type of thixojoining process for AISI D2 with AISI 304 stainless steel using a partial remelting method was proposed. This process is not based on conventional methods but can produce homogeneous properties with high surface quality and avoids the creation of a dendritic microstructure at the join zone
Summary
Cold-work tool steel has many attractive properties such as high wear resistance, high compressive strength, high hardness after hardening, and good dimension stability during heat treatment. There have been a number of reported studies on using a feedstock material with a thixotropic characteristic (globular microstructure) to weld by employing different methods such as laser welding and friction stir welding, but problems arise with these methods including porosities, loss of alloying elements, bad geometry, and softening of the heat-affected zone resulting in a nonhomogenous microstructure in the heat-affected zone caused by the remelting temperature [1,2,3]. This last effect is undesirable from a metallurgic point of view due to the lack of control of the microstructure. Deterioration of the fracture toughness, corrosion resistance, and yield strength is often attributed to the material undergoing a thermal history, which, in turn, results in making its properties different, and generally worse, than those of the rest of the bulk material in the substrate [4]
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