Characterisation of surface abrasivity and its relation to two-body abrasive wear

Abstract

In this paper a new method for numerical characterisation of the abrasivity of surfaces and relating this to two-body abrasive wear is described. In a previous work particle angularity was characterised by a newly developed numerical parameter, the quadratic spike parameter (SPQ-particles), which approximates the major protrusions of a particle by fitting quadratic functions to sections of a particle boundary. In the present work this concept is extended to the characterisation of surface profiles and a new method for characterisation of the abrasivity of surfaces is described. Initially the method developed has been used to characterise artificial model surfaces. Steel disks with a special set of profile inserts, simulating model asperities, were manufactured and their abrasivity characterised by the new method. The disks were then used in abrasive wear experiments on a pin-on-disk test rig in order to correlate the surface parameter developed with the abrasive wear rates. The profile inserts had been manufactured with known geometry that could accurately be measured by a Talysurf. Wear experiments were then conducted with chalk to make sure that the wear was only occurring in the counter sample. An excellent correlation was obtained between the wear rates and the surface abrasivity parameter, the quadratic spike parameter (SPQ-profiles) calculated from the surface profiles. In the second part of the experiments seven different types of typical mineral abrasives were used. Two-body abrasive wear experiments were conducted on specially made disks utilising these abrasives for wear surfaces. Good correlation between SPQ-profiles and wear rates was obtained for less angular grits. However, for more angular grits, such as quartz and crushed sintered alumina, this correlation was weaker due to inadequate representation of surface profile by a Talysurf, i.e. the Talysurf tip could not follow the surface exactly, leading to lower values of SPQ-profiles. The fractal dimension and R a (centre line average) values from all profiles were also calculated and neither correlated well with wear rates.