A influência do reaquecimento de camadas na microestrutura e na dureza de produtos de aço fabricados com manufatura aditiva por deposição a arco (MADA), comparando dois tipos de resfriamento: a ar e a água

Abstract

The technologies of Big Data, Internet of Things, Additive Manufacturing, among others, related to the Fourth Industrial Revolution or Industry 4.0 are already a reality nowadays. Among these technologies, Additive Manufacturing plays a key role in the success of this new technological phase that requires more flexibility and customization in production processes. One of the manufacturing processes that has attracted a lot of interest from the industry is the Wire Arc Additive Manufacturing (WAAM) process, due to the possibility of manufacturing large metal parts with low equipment cost, low material cost and low environmental impact. However, this process requires strict control of the heat accumulation generated by the type of energy source used and the high rate of material deposition, which can cause several defects in the manufactured parts. In this sense, this work analyzes the influence of layer reheating, on the microstructure and hardness, of steel products manufactured with MADA, considering two cooling conditions, one in air and the other in water. The methodology adopted was the construction of two flat products with five layers of deposited material, studying, at first, the microstructure and hardness of the third layer, without reheating caused by the thermal cycles of other layers. Subsequently, the microstructure and hardness of the third layer were compared after being reheated by the thermal cycles of the deposition of the fourth and fifth layers. The results showed that for both air and water cooling, the thermal cycles of upper layers affect the microstructure of lower layers, reducing the presence of acicular ferrite and, consequently, increasing the volumetric fraction of bainite. Regarding the mechanical property of hardness, the results showed that both for the flat product built with air cooling and for the one built with water cooling, the microhardness of lower layers is not significantly affected by the thermal cycles of the deposition of upper layers. However, there is a tendency to decrease the microhardness of the lower layers with the increase in the number of layers deposited, caused by the difficulty in dissipating heat from the higher layers.