Effect of Post-Weld Heat-Treatment on Corrosion and Microstructure Properties of Electric Arc Welded Mild Steels

Abstract

Welding has been an incredibly important process used to join metals in several industrial applications, such as manufacturing, construction, automotive and aerospace sectors. It has been reported that welded joints sometimes exhibit poor corrosion resistance, due to the changes in the weld surface or HAZ chemical composition, residual stress and metallurgical structure. Therefore, there is a need to enhance welds corrosion resistance and microstructure properties through PWHT. In this study, PWHTs effect on the corrosion and microstructure properties of two MSs, SAE 1015 and 1010, which were fused by electric metal arc welding, was examined. The MS samples, with different chemical compositions, were cut to the desired dimensions, separately welded and, thereafter, subjected to PWHT, at 650, 750, 850 and 950 ºC, for 1 h. The corrosion and microstructure properties of the PWHT MS samples immersed in 3.5 wt.% NaCl were then investigated, using PDP and SEM, respectively. For the PWHT SAE 1015 and 1010 MS samples, the lowest CR values were 34.240 and 35.793 mm/year, at 650 ºC, while the highest were 90.16 and 60.10 mm/year, at 950 ºC, respectively. For the AW SAE 1015 and 1010 MS samples, the CR values were 107.54 and 118.09 mm/year, respectively. The SEM images revealed smaller grain sizes and boundaries and less porosity for PWHT MS samples at 650 ºC than for those at 950 ºC. Therefore, the first ones are recommended for advanced industrial applications.

Assessment of Corrosion Resistance Potentials of Welded and Tempered UNS G10400 Carbon Steel in a Seawater Environment

“…This is due to the effect of the tempering process, which minimizes the ion exchange within the metal's anodic and cathodic sites [26].The corrosion rates of the as-welded and post-weld tempered samples are 0.13510, 0.06331, 0.06271, and 0.01578 mm/yr, respectively. The low corrosion values of the tempered samples could be attributed to the formation of a protective lm on the metal surface [11]. Figure 7 shows the impedance spectra for as-welded and post-weld-tempered samples of UNS G10400 carbon steel in seawater.…”

“…However, with the aid of appropriate post-weld tempering, the severity of these issues can be controlled. Several studies indicate that post-welding heat treatment (PWHT) such as annealing, normalizing, and tempering has been utilized to reduce residual stress gradients and protect welded joints from stress corrosion cracking [9][10][11][12][13][14][15]. This process mitigates concentration disparities and the formation of microgalvanic cells and equally removes hydrogen from the weld areas, preventing them from becoming brittle [16,17].…”