Experimental observations of wear in specimens tested to ASTM G98

• We examine damage induced by galling to ASTM G98 using a combination of observations and laser microscopy.
• We quantify damage in metal specimens to ASTM G98 using common surface roughness parameters.
• Recommendations for improvement of ASTM G98 are provided.

The Electric Power Research Institute (EPRI) is evaluating candidate materials for nuclear valve applications utilizing multiple wear tests standards including ASTM G98. The purpose of ASTM G98 is to assess the galling resistance of material couples, and is only intended to provide qualitative observations of the tested materials. In specific cases, such as the testing of stainless steels, this test method has provided quantifiable comparison in the form of a threshold galling stress for comparison. This same approach has not been validated for all types of materials. Specimens were tested to ASTM G98 and exhibited a range of behavior which suggested that multiple mechanisms were responsible for the visual observations. In this paper, detailed laser microscopy was applied to quantify the reported wear mechanisms. The results show, for the first time, that for some mechanisms quantitative data can be obtained to classify wear and galling to ASTM G98. Some suggestions for modifications and improvements to the standard are proposed.