Narrow gap welding is a prevalent technique used to decrease the volume of molten metal and heat required to fill a joint. Consequently, deleterious effects such as distortion and residual stresses may be reduced. One of the fields where narrow groove welding is most employed is pipeline welding where misalignment, productivity and mechanical properties are critical to a successful final assemblage of pipes. This work reports the feasibility of joining pipe sections with 4 mm-wide narrow gaps machined from API X80 linepipe using cold wire gas metal arc welding. Joints were manufactured using the standard gas metal arc welding and the cold wire gas metal arc welding processes, where high speed imaging, and voltage and current monitoring were used to study the arc dynamic features. Standard metallographic procedures were used to study sidewall penetration, and the evolution of the heat affected zone during welding. It was found that cold wire injection stabilizes the arc wandering, decreasing sidewall penetration while almost doubling deposition. However, this also decreases penetration, and incomplete penetration was found in the cold wire specimens as a drawback. However, adjusting the groove geometry or changing the welding parameters would resolve this penetration issue.
The control of cavitation erosion wear is a hindrance concerning the maintenance of hydraulic equipment's. The most used consumables to fill eroded areas are cobalt-based austenitic steels, commercially known as ''Stellites''. The current study carried out analysis of the coatings deposited via the new cold wire gas metal arc welding (CW-GMAW) process. The coatings were deposited via CW-GMAW process, variating three levels of addition wire feeding speed. The coating consisted in a three-layer deposit; the first two with an AWS ER 309L wire, via GMAW process, and the third layer employed the interaction between AWS ER 309L and Stellite 21 E wires, via CW-GMAW process. The coatings obtained an increase in cobalt values, with silicon and molybdenum variations, as well as the iron value reduction for each used feeding variation. The coatings were subjected to an accelerated erosion test, according to ASTM G32 Standards. The best obtained result corresponded to the coating with 7.2 m/min additional speed.
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