Hybrid layered manufacturing, an automatic layered manufacturing process for metallic objects, combines the best features of two well-known and economical processes, namely, weld-deposition and milling. A study of the mechanical properties like hardness and tensile strength of objects made through hybrid layered manufacturing is presented in this article. It was found that the interior matrix has negligible hardness variations in all directions. The tensile strength of the matrix displays negligible variations in the horizontal plane. However, the same for the vertical direction initially was found to be slightly lower, but this could be rectified by increasing the weld-deposition current. The ability of hybrid layered manufacturing to make composite material matrix with good material bonding has also been demonstrated. These studies help in understanding and controlling the anisotropic behavior of objects built using weld-deposition–based rapid prototyping and manufacturing techniques.

Purpose: Twin-wire welding-based additive manufacturing (TWAM) is a unique process which uses gas metal arc welding (GMAW)-based twin-wire weld-deposition to create functionally gradient materials (FGMs). Presented study aims to focus on creating metallic objects with a hardness gradient using GMAW of twin-wire weld deposition setup. Design/methodology/approach: By using dissimilar filler wires in twin-wire weld-deposition, it is possible to create metallic objects with varying hardness. This is made possible by individually controlling the proportion of each filler wire used. ER70S-6 and ER110S-G are the two filler wires used for the study; the former has lower hardness than the latter. In the current study, methodology and various experiments carried out to identify the suitable process parameters at a given location for a desired variation of hardness have been presented. A predictive model for obtaining the wire speed of the filler wires required for a desired value of hardness was also created. Subsequently, sample parts with gradient in various directions have been fabricated. Findings: For dissimilar twin-wire weld-deposition used here, it is observed that the resultant hardness is in the volumetric proportion of the hardness of the individual filler wires. This aids the fabrication of FGMs using arc based weld-deposition with localized control of hardness, achieved through the control of the ratio of wire speeds of the individual filler wires. Four sample parts were fabricated to demonstrate the concept of realizing FGMs through TWAM. The fabricated parts showed good match with the desired hardness variation. Research limitations/implications: This paper successfully presents the capability of TWAM for creating gradient metallic objects with varying hardness. Although developed using ER70S-6 and ER110S-G filler wire combination, the methodology can be extended for other filler wire combinations too for creating FGMs Originality/value: GMAW-based twin-wire welding for additive manufacturing is a novel process which uses dissimilar filler wires for creating FGMs. This paper describes methodology of the same followed by illustration of parts created with bi-directional hardness gradient.