Erosion Testing

Erosion Testing
Erosion is defined as progressive loss of original material from a solid surface due to mechanical interaction between that surface and a fluid, a multicomponent fluid, or impinging liquid or solid particles [ASTM G40-99]. As all kind of wear, erosion causes costly damage in many machine components. The erosion mechanism depends on the material and is different for brittle and ductile materials, and therefore erosion has been divided into brittle and ductile erosion. The parameters affecting erosion are varied and include material properties, environmental factors and process parameters. The erosion modes were reviewed according to the media causing erosion, various erosion modes are described according to the erosive medium.
Ceramic materials subjected to different operating conditions such as the operations of bearings, refractories or valves. The most common type of erosive wear relevant to ceramic materials occurs due to contact with high velocity substance. For example, in coal conversion plants, high velocity (20 m/s) coal, coal ash particles in transfer lines erode refractory insulation used as liners. Erosion also occurs on space vehicle windows and on turbine blades fig 18. Ceramic materials show both ductile and brittle modes of solid particle erosion. The ductile erosion in glass and polycrystalline ceramics could occur upon impact with small (9?m) particles. A transition to brittle behavior occurred when using larger (500-100 mesh) particles. The transition from ductile to brittle behavior was demonstrated by impact angle versus erosion curves.