Abstract
At any point in the fabrication and installation of Grade 91 components, undesirable metallurgical conditions can develop as a result of incorrect heat treatment. Industry techniques for locating and evaluating these microstructures using nondestructive methods are necessary. Field hardness testing is commonly utilized to characterize Grade 91 steel installed in plants. However, it is apparent that there are numerous variables that can affect the results of field hardness testing. Thus, the results can vary significantly depending on the equipment and procedures used. The present study has been undertaken to identify the accuracy of hardness measurements made under controlled laboratory conditions. Measurements were performed on samples that had been subjected to a range of different tempering conditions. The trend in these data provides information relevant to understanding the metallurgical behavior of this steel. Comparison of the data also indicates how measurements made using different hardness testers and methods can be used to assess component condition.
