| Popis: |
Preventing failure due to corrosion poses a challenge to the oil and gas industry. A cost-effective way to prevent such failures is the application of corrosion-resistant nickel-based weld overlays using arc welding processes. Previous research performed at The Ohio State University indicates low heat input GMAW processes, such as cold metal transfer (CMT), produce weld overlays which corrode up to ten times slower than overlays produced with cold wire GTAW [1, 2], with up to ten times higher deposition rates [3]. However, formation of lack of fusion and lack of penetration defects has been a major concern related to the widespread application of low heat input GMAW processes in the industry. In this study, optimal windows of CMT welding parameters for producing defect-free welds were established using a design of experiment approach. CMT weld overlays were compared with hot wire (HW)-GTAW overlays currently used in industry with respect to bead characteristics, microstructure, and process capability. As compared with the HW-GTAW process, the CMT process produced weld overlays with up to four times lower dilution, seven times smaller interdendritic arm spacing, and four times higher deposition rates. Additionally, average heat affected zone and fusion boundary hardness values in the CMT overlays were below 248 HV0.1 and may not require the post weld heat treatment specified by NACE MR0175. |
