Welding is an important joining technology, and is highly dependent on the process choice, consumables used, operating parameters, and operator proficiency.
Thus, inspection procedures, both nondestructive and destructive, are required to control the process and guarantee quality. Metallographic examination is a key tool in the destructive examination of weldments, both as a process control tool and as a post-mortem examination of failed components. Macrostructure must also be examined, which can be done on sections after grinding or polishing. Macrostructural examination is used to learn about the weld geometry, the depth of weld metal penetration, the magnitude of the heataffected zone, and to detect cracks and voids. Microstructural examination is used to determine the mode of cracking and the cracking mechanism and to identify phases or constituents in the weld metal, heat-affected zone, and base metal including nonmetallic inclusions, as related to governing specifications, fitness for service, or cause of failure.