Abstract
ASTM A743 CA6NM steel is used in the manufacturing of hydraulic turbines components. Multipass welding is commonly used for their fabrication or repairing. In this work, two different vibratory welding procedures were studied: vibration applied during welding (VWC) and vibration applied after welding (VSR). Results have shown that in both conditions, CA6NM steel presented a martensitic microstructure, in which the VSR welded joint presented column-shaped packets and fine martensite delineating the individual beads, while VWC joint presented grain refinement. Heat affected zones (HAZ) presented δ-phase in small amounts for both conditions in the regions which reached higher temperatures. VSR and VWC conditions presented similar behavior in terms of hardness, HAZ hardness values being close to those of the weld metal, except for the root regions, where higher values were obtained. Charpy-V results showed that HAZs presented higher impact values than those of the weld metal. The low impact values of the weld metal were attributed to presence of inclusions from the welding electrode.
Highlights
The Brazilian energy matrix is based on the use of electricity generated by hydroelectric plants, which use different types of hydraulic turbines
The results suggest a single-phase martensitic microstructure for all joints, except for the post weld heat treatment (PWHT) joint which presented near 10 % retained austenite (Silva et al, 2017) in addition to martensite
The heat affected zone (HAZ) of both VSR and VWC joints presented δ-phase in small amounts and no reversed austenite was present in the region that reached higher temperatures during welding procedure
Summary
The Brazilian energy matrix is based on the use of electricity generated by hydroelectric plants, which use different types of hydraulic turbines. Hydraulic turbines can present several problems, cavitation erosion and cracking in high stress concentration regions being responsible for the major damage. These defects are repaired by welding process (Prado, 2004; Pukasiewicz, 2008). It is difficult to be carried out for on site repairs To solve these problems, many studies have been conducted to find alternatives and new procedures for welding processes (Jurcius, Valiulis, & Cernasejus, 2010; Robbins, 2004; Wu, 2000; Wu, Lin, & Chen, 1999)
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