Microstructure and mechanical properties of high strength steel deposits obtained by Wire-Arc Additive Manufacturing

Wire-arc additive manufacturing has become an alternative way to produce industrial parts. In this work 15 kg walls are built with an effective building rate of 4.85 kg/h using an ER100 wire providing good tensile properties and toughness under welding conditions. The thermal evolution of the walls during manufacturing is measured by thermocouples and an IR camera: it depends on process parameters, deposit strategy and the size of the part. The walls are then characterised as deposit and after heat treatment through hardness, tensile and Charpy-V notch tests. The results show a fine microstructure with unexpected retained austenite and coarse allotriomorphic ferrite in the as deposited walls. The final hardness values vary from about 220 to 280 HV2; the yield stress and tensile strength are 520 and 790 MPa, respectively, and a toughness of about 50 J is obtained at room temperature. The heat treatment transforms the retained austenite, leading to an improvement of the yield stress to 600 MPa

Etat de l’art des technologies de soudage en chanfrein étroit

Les procédés de soudage en chanfrein étroit permettent de réaliser des assemblages bout à bout de pièces de très forte épaisseur en limitant le nombre de passes, donc le temps de soudage et les déformations. Ces procédés sont par conséquent largement utilisés dans le secteur nucléaire, pour la fabrication de cuves de réacteur, de générateurs de vapeur et de pressuriseurs. des équipements spécifiques de soudage en chanfrein étroit sont disponibles, notamment pour les procédés TIG, MAG et à l’arc sous flux en poudre. Leur mise en oeuvre nécessite cependant beaucoup de rigueur aussi bien lors de l’établissement des modes opératoires de soudage qu’en phase de production

Microstructure and mechanical properties of Ti-6Al-4V laser welds for airplane floor manufacturing application

International audienceOwing to its high strength-to-weight ratio, corrosion resistance and compatibility with carbon fibre composites, Ti-6Al-4V is a good candidate for the replacement of aluminium alloys in the manufacture of aircraft floor structure, whenever enhanced corrosion resistance is required. However forming and machining of Ti -6Al-4V is not straightforward and the cost of such an alloy makes rail manufacture from machining bars a non-viable solution. A better way to manufacture titanium alloy rails is to divide a rail into several components with fairly simple shape, which can then bejoined before limited machining to obtain the final shape. Laser welding is well suited for joining titanium alloys, as it is fast, precise and generates far less deformations than other welding processes. In this study, a 10kW fibre laser was used for joining two different grades of 5 mm thick Ti-6Al-4V plates. A comprehensive study taking into account on the laser process parameters and characteristics of both grades has been carried out to minimize distortion and to achieve sound and reproducible welds without oxide. The structure of each welded zone was examined both by optical and electron microscopy. Micro texture analyses were performed on samples before and after welding, in order to evaluate texture modifications. Differences in terms of mechanical properties, as shown by uniaxial tensile tests, were interpreted on the basis of base material initial microstructures as well as the microstructure of assemblies