Engineering topics
Publications and source records attributed to Munafo, P..
Variable-polarity plasma-arc methods produces better welds at lower cost than gas-shielded tungsten-arc welding in assemblies. Weld porosity very low and costs of joint preparation, depeaking, inspection, and weld repair minimized.
Inconel 718, nickel-based alloy used extensively for high-temperature structural service, welded repeatedly without detriment to its strength. According to NASA report, tests show 12 repairs on same weld joint do not adversely affect ultimate tensile strenth, yield strength, fatigue strength, metallurgical grain structures, or ability of weld joint to respond to post weld heat treatments.
The effects of repeated weld repairs on the metallurgical characteristics, high cycle fatigue (HCF), and tensile properties of Inconel 718 butt weld joints were determined. A 1/4 in thick plate and a 1/2 in thick plate were used as well as tungsten inert gas welding, and Inconel 718 filler wire. Weld panels were subjected to 2, 6, and 12 repeated repairs and were made in a highly restrained condition. Post weld heat treatments were also conducted with the welded panel in the highly restrained condition. Results indicate that no significant metallurgical anomaly is evident as a result of up to twelve repeated weld repairs. No degradation in fatigue life is noted for up to twelve repeated repairs. Tensile results from specimens which contained up to twelve repeated weld repairs revealed no significant degradation in UTS and YS. However, a significant decrease in elongation is evident with specimens (solution treated and age hardened after welding) which contained twelve repeated repairs. The elongation loss is attributed to the presence of a severe notch on each side (fusion line) of the repair weld bead reinforcement.