Lack of assurance of quality with additively manufactured (AM) parts is a key technological barrier that prevents manufacturers from adopting AM technologies, especially for high-value applications where component failure cannot be tolerated. Developments in process control have allowed significant enhancement of AM techniques and marked improvements in surface roughness and material properties, along with a reduction in inter-build variation and the occurrence of embedded material discontinuities. As a result, the exploitation of AM processes continues to accelerate. Unlike established subtractive processes, where in-process monitoring is now commonplace, factory-ready AM processes have not yet incorporated monitoring technologies that allow discontinuities to be detected in process. Researchers have investigated new forms of instrumentation and adaptive approaches which, when integrated, will allow further enhancement to the assurance that can be offered when producing AM components. The state-of-the-art with respect to inspection methodologies compatible with AM processes is explored here. Their suitability for the inspection and identification of typical material discontinuities and failure modes is discussed with the intention of identifying new avenues for research and proposing approaches to integration into future generations of AM systems

The electrochemical corrosion performance of laser clad Inconel 625 wire in a de-aerated 3.5 wt% NaCl solution was investigated. The microstructure of the clad beads before and after the corrosion testing was examined using a combination of optical microscopy, scanning electron microscopy (with energy dispersive X-ray analysis) and X-ray diffraction. Well bonded, minimally diluted, pore- and crack-free single bead and multiple (overlapped) beads of Inconel 625 wire were successfully deposited. The clad beads comprise dendritic γ-Ni (FCC) matrix and interdendritic precipitates which are Mo- and Nb-rich. The microstructural evolution of a typical clad bead is observed to begin with columnar dendrites, at the clad-substrate interface, growing vertically to the substrate. This blends into horizontal columnar dendrites near the top region. High integrity laser coating (multiple beads) of Inconel 625 wire with a minimal dilution ratio of 4.5% is found in this study. The corrosion performance of the coating, which degrades with increasing Fe dilution, is very close to that of wrought Inconel 625 but superior to the wrought 304L stainless steel. The stainless steel exhibited localised (pitting) corrosion however, it was fully protected by the Inconel 625 wire laser coating in the saline solution