Development and use of combined wear testing equipment for evaluating galling and high stress sliding wear behaviour

Galling is a severe form of wear characterized by localized, macroscopic material transfer or removal of material when two solid surfaces experience relative sliding under load. The current paper describes the development of a wear testing machine capable of testing both galling resistance and sliding wear behaviour (pin-on-disc) at high stress levels. For evaluating galling resistance using this equipment, a stationary button is placed in contact with a rotating flat block at a desired pressure by means of a hydraulic system. The block is rotated through one revolution and both the specimens are inspected for the presence of galling as per ASTM G98-91 galling procedure. In this, button axis coincides with the rotating block axis. Surface damage as a result of galling is also evaluated by applying the desired load to the button specimen and rotating the block about its vertical axis, back and forth 10 times through 120° in 90 s. To evaluate sliding wear behaviour, button axis is offset to a required distance and it is used as pin-on-disc apparatus. The apparatus developed in this work could be successfully used for assessing the sliding wear behaviour, as also the galling resistance. Various features of this apparatus and results from the tests are discussed in this paper.