What type of damage can be revealed by conducting hardness testing on the base metal?

Hardness testing is a valuable tool in assessing the mechanical properties of materials, particularly when it comes to determining their strength. The hardness of a material directly correlates with its ability to withstand deformation and, consequently, its overall mechanical strength. When hardness testing is performed on the base metal of a pressure vessel, the results can indicate whether the material's strength meets the necessary requirements for operational safety and integrity. High hardness values typically suggest greater resistance to wear and deformation, while lower values may indicate potential issues like softening or weakening of the metal.

This testing does not provide direct insights into corrosion resistance, weld integrity, or thermal fatigue. While those factors are crucial in evaluating the overall performance and safety of pressure vessels, they focus on different properties. Corrosion resistance pertains to the material's ability to withstand chemical attacks, weld integrity assesses the quality and soundness of welds, and thermal fatigue relates to the material's capacity to resist failure under cyclic thermal loads. Thus, hardness testing is specifically aligned with evaluating mechanical strength, making it the correct choice in this context.