Multiscale study of different types of interface of a buffer material in powder-based directed energy deposition: Example of Ti6Al4V/Ti6Al4V - Mo/Mo - Inconel 718

Abstract

When it is difficult to deposit a material A on a material B, it is possible to create a Functionally Graded Material (FGM) using a buffer material between them to avoid the appearance of defects. The literature shows that it is very difficult, nay impossible, to have an efficient metallurgical bond between Ti6Al4V and Inconel-Mo alloys without cracks, porosities or delamination. A buffer material is therefore needed (here 25% Ti6Al4V -75% Mo) and the fine analysis of the two interfaces thus created makes it possible to define the relevance of the choice of the buffer. Moreover, the understanding of the phenomena taking place at the interface allows the preservation of the structural integrity of a FGM made by additive manufacturing. CLAD® powder-based directed energy deposition allows the building of parts containing FGM and/or buffer materials directly during the process. The study of the interfaces at both sides of the buffer material is essential. In this paper, the first interface 100 Ti6Al4V / 25 Ti6Al4V -75 Mo (in wt%) is smooth, suggesting that there has been diffusion between both alloys. The second one, 25 Ti6Al4V -75 Mo / 30 Inconel 718 -70 Mo, contains numerous exotic structures between both alloys. For such a sharp interface, we show in this paper that a microscopic study is not sufficient, but a finer scale is necessary to have a good metallurgical insight. Thus, EDS, TKD and X-ray crystallography were performed right on this interface and revealed three main structures: a hexagonal matrix, a cubic structure and an ordered hexagonal one. The hexagonal matrix appears to consist of Ni 3 Ti and the ordered hexagonal one of NiMo.

Effects of Processing Parameters on Functionally Graded Materials for Industrial Components Repair

“…Preheat treatment is a solution to reduce residual stresses in FGMs, by reducing the cooling rate of both the substrate and the cladding [19,20], and attenuating the difference in thermal expansion coefficients between the several powders [21]. Thus, preheated substrates reduce the susceptibility to the formation of cracks, promoting better mechanical properties [22,25].…”

Ta/Cu transition region in TC4/Inconel718 bimetallic structure fabricated by laser deposition manufacturing

“…The current solution is to select a suitable material as a transition interlayer between titanium and the nickel-based alloy to inhibit the formation of Ti–Ni brittle IMCs. Thiriet et al [13] and Oliveira et al [14] used a Mo gradient transition layer and a pure Nb intermediate layer as a transition layer between titanium and nickel-based alloy. The formation of Ti–Ni IMCs was inhibited successfully.…”

A study on the relationship between spectral characterization and composition of plasma in laser additive manufacturing of gradient materials

“…316 L is of excellent mechanical properties, and aluminum alloys are widely used because of their low density. The joining of two materials with very different thermophysical properties is not easy (Thiriet et al , 2019), and additive manufacturing of functional gradient materials can solve this difficult problem, ensuring that the specimen is free of cracks, porosity and delamination. So the 316 L/AlSi10Mg FGM is significantly meaningful for quality assurance, lightweight development and cost-saving in the automotive, aerospace and other fields (Ansari et al , 2021).…”