Caracterização de pré-formas de aços 2,25Cr1Mo fabricadas via manufatura aditiva por deposição a arco com e sem resfriamento ativo por quase-imersão

Abstract

Wire arc additive manufacturing (WAAM) has been highlighted in the manufacture of large objects with geometry used in structural applications. However, there are currently more questions than answers about the components produced by this manufacturing process, especially with regard to the critical properties determined at the end of the deposition process. In this context, the present work aims to determine the microstructure and the mechanical and electrochemical behavior of 2.25Cr-1Mo steel preforms (ER90S-B3) produced by MADA, built with different cooling strategies, subjected to normalising and tempering heat treatments. Also, compare with traditional ASTM A335 Gr. P22 material that has similar chemical composition. For this purpose, microstructural analysis techniques (MO, SEM, XRD), microhardness tests, tensile and impact tests were used. The results showed the existence of three different areas that were repeated along the construction direction in the XZ and YZ planes of the preforms. The morphologies of the phases formed in these different regions were different due to the effect of the thermal cycles imposed during the deposition of the material. The microhardness profiles obtained along these planes showed that the hardness of the components varies for each of the typical areas as result of the microstructural heterogeneity generated in the deposited preforms. Furthermore, the microhardness measurements along the height of the preforms indicate that the presence of active cooling during the deposition process reduces the gradient of this property. The tensile curves obtained for both deposition conditions showed that the active cooling strategy allowed the achievement of better properties regarding yield strength, ultimate tensile strength and elongation at fracture of the component. The results also revealed that normalizing + tempering heat treatments decreased the mechanical strength of the component, but significantly increased impact toughness. The potentiodynamic curves indicated that WAAM preforms exhibited better corrosion behavior than the P22 laminated steel in the passivation region.