Investigating the Linear Thermal Expansion of Additively Manufactured Multi-Material Joining between Invar and Steel

Abstract

This work investigated the linear thermal expansion properties of a multi-material specimen fabricated with Invar M93 and A36 steel. A sequence of tests was performed to investigate the viability of additively manufactured Invar M93 for lowering the coefficient of thermal expansion (CTE) in multi-material part tooling. Invar beads were additively manufactured on a steel base plate using a fiber laser system, and samples were taken from the steel, Invar, and the interface between the two materials. The CTE of the samples was measured between 40 °C and 150 °C using a thermomechanical analyzer, and the elemental composition was studied with energy dispersive X-ray spectroscopy. The CTE of samples taken from the steel and the interface remained comparable to that of A36 steel; however, deviations between the thermal expansion values were prevalent due to element diffusion in and around the heat-affected zone. The CTEs measured from the Invar bead were lower than those from the other sections with the largest and smallest thermal expansion values being 10.40 μm/m-K and 2.09 μm/m-K. In each of the sections, the largest CTE was measured from samples taken from the end of the weld beads. An additional test was performed to measure the aggregate expansion of multi-material tools. Invar beads were welded on an A36 steel plate. The invar was machined, and the sample was heated in an oven from 40 °C and 160 °C. Strain gauges were placed on the surface of the part and were used to analyze how the combined thermal expansions of the invar and steel would affect the thermal expansion on the surface of a tool. There were small deviations between the expansion values measured by gauges placed in different orientations, and the elongation of the sample was greatest along the dimension containing a larger percentage of steel. On average, the expansion of the machined Invar surface was 42% less than the expansion of the steel surface. The results of this work demonstrate that additively manufactured Invar can be utilized to decrease the CTE for multi-material part tooling.

A Review on Multiplicity in Multi-Material Additive Manufacturing: Process, Capability, Scale, and Structure

“…They mentioned that a good microhardness value and a great metallurgical bond are obtained at the interface. The thermal expansion properties of bi-metallic Invar M93 beads on an A36 steel base fabricated using laser-based wire AM were investigated by Arbogast et al [114]. They deduced that the multi-material AM of Invar considerably decreased the coefficient of thermal expansion of the entire system.…”

“…Implementing MMAM in large-scale production enables the introduction of assembly-free construction [21]. The flexibility of MMAM with regard to the scale of production provides several benefits in comparison to single-material AM, including but not limited to functional integration across distinct and/or different materials [133], a reduction in the part count [21,133], transitional grading across materials [114], the ability to adjust properties across the volume of the product [134], and 4D printing. Although only limited research results and examples of practical implementation are available for large-scale MMAM, the initial prototype productions are very promising and pave the way for further developments and the introduction of new concepts in the realm of large-scale MMAM.…”

Synthetization of TiC surface hardening using TIG melting technique - The effect of working distance

“…When the pools are excessively melted, it would require overlapping distances to be reduced to maintain equal depth on the weak substrate. The number of passes needed to span for a coverage is also reduced when overlapping percentages are reduced [16][17][18].…”