The sliding wear behavior of cobalt-based hardfacing alloys used in steam valve applications©

The tribological characteristics of a low carbon cobalt-based alloy were, compared to a higher carbon cobalt-based alloy for application in a steam valve. In order to simulate the severe conditions typical for a steam valve, wear tests were conducted using a pin-on-rotating ring test configuration in an cobalt-based steam atmosphere at 260° C After the wear tests were completed, both optical and scanning electron microscopy was used to determine the mode of material removal during the wearing process. A statistical analysis of the wear data involving several parameters did not establish a clear correlation between material properties and the observed wear rates. Nevertheless, the tribological performance of the lower carbon cobalt-based alloy was similar to the higher carbon cobalt-based alloy under the test conditions of high temperature steam. In both cases, adhesive wear was found to be the dominant material removal mechanism.