Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / As ligas de nÃquel podem ser utilizadas na uniÃo de juntas dissimilares de aÃos carbono baixa liga. Uma das finalidades desta uniÃo à evitar a formaÃÃo de trincas induzidas pelo hidrogÃnio. Existe uma limitaÃÃo por norma que impÃe a temperatura de interpasse mÃxima de 150ÂC para soldagem com ligas de nÃquel. Contudo, a temperatura de interpasse baixa reduz a produtividade e consequentemente aumenta os custos de fabricaÃÃo. Um estudo que avalia como a temperatura de preaquecimento/interpasse na soldagem dissimilar influencia as alteraÃÃes metalÃrgicas e propriedades mecÃnicas à oportuno. Desta forma, o objetivo geral deste trabalho à avaliar o efeito do aumento da temperatura de interpasse nas alteraÃÃes metalÃrgicas e nas propriedades mecÃnicas de juntas dissimilares soldadas do aÃo ASTM A182-F22 com diferentes ligas de nÃquel. Foram realizadas soldagens MIG/MAG automÃtica em juntas do aÃo (ASTM A182-F22) utilizando diferentes ligas de nÃquel como metal de adiÃÃo e diferentes temperaturas de interpasse (35ÂC, 150ÂC e 350ÂC). A energia de soldagem foi mantida constante (1,0 kJ/mm). Baseado nos resultados obtidos o aumento da temperatura de preaquecimento tende a reduzir a fraÃÃo de precipitados, decorrente do aumento da diluiÃÃo. O coeficiente de distribuiÃÃo do Mo e Nb diminuem com o aumento do teor de ferro na solda. Isto, por sua vez, torna mais forte a segregaÃÃo destes elementos. A temperatura de interpasse tendeu a reduzir a dureza da (ZTA-GG), por conta da reduÃÃo da velocidade de resfriamento. Nos ensaios de traÃÃo os corpos de prova romperam na regiÃo referente ao metal de base. Houve uma reduÃÃo no limite de escoamento nas condiÃÃes soldadas com temperatura de 350ÂC, sendo uma possÃvel causa a precipitaÃÃo de carbonetos devido ao preaquecimento e aos multipasses. Os ensaios de Charpy-V indicaram que, de uma forma geral, o aumento da temperatura de interpasse reduziu a tenacidade na zona fundida. A energia absorvida na interface sofreu reduÃÃo com o aumento da temperatura de interpasse, decorrente do aumento da descarbonetaÃÃo. O tempo de soldagem foi reduzido de forma considerÃvel com o aumento de temperatura de interpasse, entretanto, deve-se avaliar as alteraÃÃes na ZTA e ZF. / Nickel alloys can be used to weld dissimilar joints of low alloy carbon steels. One of the purposes of this union is to avoid the formation of hydrogen induced cracking. According codes and standard there is a limitation that imposes the maximum interpass temperature at 150ÂC for welding using nickel alloys. However, the low interpass temperature reduces productivity and increases manufacturing costs. A study that evaluates effect of the preheating and interpass temperature of dissimilar welds on the metallurgical changes and mechanical properties is of great relevance. In this way, the general objective of this study is to assess the effect of interpass temperature on metallurgical changes and mechanical properties of dissimilar welded joints among ASTM A182-F22 steel and different nickel-based alloys. GMAW were carried out on joints of steel (ASTM A182-F22) using different nickel-based alloys as filler metal and different interpass temperatures (35ÂC, 150ÂC and 350ÂC). The heat input was kept constant (1.0 kJ/mm). Based on the results obtained it was observed that increasing preheating temperature there is a tends to reduce the precipitates content, because of dilution. The distribution coefficient of Mo and Nb decrease with the increase of iron content in the fusion zone, making stronger the segregation of these elements. Interpass temperature tend to reduce the HAZ hardness, due to the in cooling rate reduction caused by increase interpass temperature. In the tensile tests failure in the base metal. There was a reduction in yield strength for welds produced with 350ÂC preheat temperature, being a possible cause the precipitation of carbides due to preheating and multipasses. The Charpy-V tests indicated that, generally, the increase in interpass temperature reduced the toughness in the fusion zone. The absorbed energy by the interface dropped when interpass temperature increase. The welding time was considerably reduced with the interpass temperature increase, however, it should be to considerate changes in HAZ and fusion zone.

The overall goal of this work is to create an open-source digital twin of the wire arc directed energy deposition process using robot operating system 2 for interpass temperature regulation of a maraging steel alloy. This framework takes a novel approach to regulating the interpass temperatures by using in-situational infrared camera data and a closed loop feedback control that is enabled by robot operating system 2. This is the first implementation of robot operating system 2 for wire arc directed energy deposition and this framework outlines a sensor and machine agnostic approach for creating a digital twin of this additive manufacturing process. In-situ control of the welding process is conducted on a maraging steel alloy demonstrating interpass temperature regulation leads to improved as-built surface roughness and more consistent as-built hardness. An evaluation of three distinct weld modes: Pulsed MIG, CMT MIX, and CMT Universal and two primary process parameters: travel speed and wire feed speed was conducted to identify suitable process windows for welding the maraging alloy. Single track welds for each parameter and weld mode combination were produced and evaluated against current weld bead metrics in the literature. Non destructive profilometry and destructive characterization were performed on the single track welds to evaluate geometric features like wetting angle, dilution percentage, and cross sectional area. In addition, the role of material feed rate on heat input and the cross sectional area was examined in relation to the as-built hardness. The robot operating system 2 digital twin provides a visualization environment to monitor and record real time data from a variety of sensors including robot position, weld data, and thermal camera images. Point cloud data is visualized, in real time, to provide insight to the captured weld meta data. Capturing in-situ data from the wire arc directed energy deposition process is critical to establishing an improved understanding of the process for parameter optimization, tool path planning, with both required to build repeatable, quality components. This work presents an open-source method to capture multi-modal data into a shared environment for improved data capture, data sharing, data synchronization, and data visualization. This digital twin provides users enhanced process control capabilities and greater flexibility by utilizing the robot operating system 2 as a middleware to provide interoperability between sensors and machines.