Effect of post-treatments on the fatigue behaviour of 316L stainless steel manufactured by laser powder bed fusion

This paper investigates the influence of post treatments on the fatigue properties of 316L stainless steel produced by laser powder bed fusion. Miniaturised fatigue samples are built in vertical orientation with optimised process conditions to result in very low porosities and minimal scatter in results. Fatigue performance is evaluated for two different material conditions: as-built and stress-relieved, at a nominal load ratio of −1. Furthermore, the samples are tested with and without surface machining. A thorough microstructural and fractographic analysis is performed to evaluate the impact of the main fatigue influencing factors. The results show that the fatigue behaviour of machined samples with and without stress relief heat treatment exceeds that of conventionally manufactured 316L. © 2019 Elsevier Lt

Towards work-hardenability of Ti-6Al-4V through a quenching and partitioning approach

In this work, the work-hardening ability of Ti-6Al-4V alloy was investigated using a quenching and partitioning strategy on dual-phase Ti-6Al-4V samples. As recently reported [1], it is known that a sub-transus thermal treatment followed by water quenching are able to generate a dual phaseα + α’ microstructure with a remarkable work-hardening coupled with an interesting balance between strength and ductility. Based on this statement, several heat treatments at various subtransus temperatures were performed on as-forged Ti-6Al-4V. In such a way, the respective volume fraction of each phase along with the size and the distance to the equilibrium composition of the quenched martensite are taken as microstructural variables to decompose the work hardenability of dual-phase Ti-6Al-4V alloys into respective contributions. Then, annealing of the metastable α + α’ microstructure was performed to trigger the α’ martensite decomposition, involving a partitioning of the alloying elements. The present investigation was carried out on wrought material. The quenching and partitioning parameters led to a wide range of mechanical properties and associated work-hardening behaviour. The as-quenched and further annealed microstructures were characterized by Scanning Electron Microscopy (SEM). The resulting mechanical properties were discussed and compared to those of as-forged material.</jats:p

Towards work-hardenability of Ti-6Al-4V through a quenching and partitioning approach

In this work, the work-hardening ability of Ti-6Al-4V alloy was investigated using a quenching and partitioning strategy on dual-phase Ti-6Al-4V samples. As recently reported [1], it is known that a sub-transus thermal treatment followed by water quenching are able to generate a dual phaseα + α’ microstructure with a remarkable work-hardening coupled with an interesting balance between strength and ductility. Based on this statement, several heat treatments at various subtransus temperatures were performed on as-forged Ti-6Al-4V. In such a way, the respective volume fraction of each phase along with the size and the distance to the equilibrium composition of the quenched martensite are taken as microstructural variables to decompose the work hardenability of dual-phase Ti-6Al-4V alloys into respective contributions. Then, annealing of the metastable α + α’ microstructure was performed to trigger the α’ martensite decomposition, involving a partitioning of the alloying elements. The present investigation was carried out on wrought material. The quenching and partitioning parameters led to a wide range of mechanical properties and associated work-hardening behaviour. The as-quenched and further annealed microstructures were characterized by Scanning Electron Microscopy (SEM). The resulting mechanical properties were discussed and compared to those of as-forged material

Titanium Alloy Repair with Wire-Feed Electron Beam Additive Manufacturing Technology

Wire feeding can be combined with different heat sources, for example, arc, laser, and electron beam, to enable additive manufacturing and repair of metallic materials. In the case of titanium alloys, the vacuum operational environment of electron beam systems prevents atmospheric contamination during high-temperature processing and ensures high performance and reliability of additively manufactured or repaired components. In the present work, the feasibility of developing a repair process that emulates refurbishing an “extensively eroded” fan blade leading edge using wire-feed electron beam additive manufacturing technology was examined. The integrity of the Ti6Al4V wall structure deposited on a 3 mm thick Ti6Al4V substrate was verified using X-ray microcomputed tomography with a three-dimensional reconstruction. To understand the geometrical distortion in the substrate, three-dimensional displacement mapping with digital image correlation was undertaken after refurbishment and postdeposition stress relief heat treatment. Other characteristics of the repair were examined by assessing the macro- and microstructure, residual stresses, microhardness, tensile and fatigue properties, and static and dynamic failure mechanisms

Titanium Alloy Repair with Wire-Feed Electron Beam Additive Manufacturing Technology

Wire feeding can be combined with different heat sources, for example, arc, laser, and electron beam, to enable additive manufacturing and repair of metallic materials. In the case of titanium alloys, the vacuum operational environment of electron beam systems prevents atmospheric contamination during high-temperature processing and ensures high performance and reliability of additively manufactured or repaired components. In the present work, the feasibility of developing a repair process that emulates refurbishing an “extensively eroded” fan blade leading edge using wire-feed electron beam additive manufacturing technology was examined. The integrity of the Ti6Al4V wall structure deposited on a 3 mm thick Ti6Al4V substrate was verified using X-ray microcomputed tomography with a three-dimensional reconstruction. To understand the geometrical distortion in the substrate, three-dimensional displacement mapping with digital image correlation was undertaken after refurbishment and postdeposition stress relief heat treatment. Other characteristics of the repair were examined by assessing the macro- and microstructure, residual stresses, microhardness, tensile and fatigue properties, and static and dynamic failure mechanisms.</jats:p

Titanium Alloy Repair with Wire-Feed Electron Beam Additive Manufacturing Technology

status: accepte