Direct energy deposition processes that utilize wire feedstock have been deployed to deposit and fabricate near net shape functional metal parts at high deposition rates. Is this just multi-pass welding or is there more to it? Should the material requirements for additive be the same as those defined for welding? Is weld quality the same as part quality? A large metal additive part fabricated using a robotic wire arc additive system will be used to demonstrate the similarities and identify critical differences between essential variables for welding and additive manufacturing. The opportunities for both welding and additive manufacturing to learn and leverage one another to develop unique and novel materials, process controls and further fundamental understanding of metal deposition processes will be outlined.
The use of High-Velocity Thermal Spray (HVTS) technology has been well adopted for sour conditions; particularly where low, or locally low, pH conditions result in corrosion and shell thinning. High alloy systems resistant to low pH or acidic conditions are effective at providing a metallurgical barrier, protecting the underlying substrate from material loss. Moreover, HVTS processes have also been employed for mitigating environmentally induced cracking (EIC) in sour service. This paper discusses the suitability and performance of modified HVTS alloys for service where high pH general corrosion or caustic cracking (CSCC) may occur. Extensive testing has been undertaken in both ambient and high pressure and temperature autoclave conditions to better understand material performance in caustic environments. While Nickel Alloy 200 and Monel 400 may be deemed appropriate based on traditional material selections, thermal spray process considerations in the material deposition and the impact of ancillary elements in the process stream, such as halides, render these alloys unsuitable. More complex Nickel alloy cladding systems are evaluated in this study with suitable material recommendations for remediation without the deleterious heat impact of welding or to protect surfaces where heat affected zones have been created and post weld heat treatment is problematic.