Welding Inspection & Metallurgy API ICP Self Study Notes

The Vickers hardness value is preceded by the designation (HV). The Vickers
hardness number is the same as the diamond pyramid hardness number
(DPH). In-service hardness testing may involve the use of portable variations
of the above-described methods. Alternatively, varying techniques based on
rebound, indentation resistance or comparator indentations may be applied
and the results related to the hardness scales more commonly accepted.
Whatever technique is employed may well be acceptable as long as it
produces verifiable and consistent results.
Various codes and standards place hardness requirements on metals and
welds. One should compare test results for the material or welding
procedures with the applicable standards to assure that the requirements for
hardness testing are being met, and that the test results are satisfactory with
that specified by the applicable code. There are often in-service degradation
requirements, which are hardness related. For example, susceptibility to wet
H 2 S cracking in carbon steel is reduced if hardness levels are maintained
below HRC 22.