Measurement of friction in galling testing – An example of its use in characterising the galling behaviour of hardfacings at ambient and elevated temperature

Galling is a category of severe adhesive wear that is defined by surface damage arising between sliding solids, distinguished by macroscopic, usually localized, roughening and creation of protrusions above the original surface. The identification of galling is through a visual observation of the tested surface and is therefore inherently subjective. Due to the microscopic processes behind the onset of galling being poorly understood, further work is needed to understand the behaviour of different materials under galling conditions, both at room temperature and at elevated temperature. The current paper describes the development of a new galling testing apparatus, broadly under the ASTM G196 configuration with the addition of in-situ torque measurements, an automated worm drive for sample rotation as well as band heaters providing capability for testing at elevated temperatures up to a maximum applied stress of 950 MPa. Results from galling tests conducted at room temperate and 300 °C for both Stellite 6 (Co-based) and Tristelle 5183 (Fe-based) hardfacings are presented. The results show that the galling resistance of Tristelle 5183 is significantly reduced at elevated temperature (