A closer look at the ductile-brittle transition in solid particle erosion

Two types of solid particle erosion are often distinguished: brittle erosion and ductile erosion. In the first case, material is removed by crack formation (maximum erosion at 90° impact angle), in the latter case by cutting and ploughing (maximum erosion around 30° impact angle). When very low particle kinetic energies are used to erode brittle targets, the impacts are not powerful enough to initiate cracks and the erosion is ductile instead of brittle. This paper looks at the transition from brittle to ductile erosion for three brittle materials: sodalime glass, Pyrex glass and single crystalline less than or equal 100> silicon. Besides the erosion rate, we also measure the "erosion classification value" (ECV), which is the ratio of the erosion rate at 45° and 90° impact angle (ECV approximately equals 0.45 for brittle erosion and >1 for ductile erosion). The change of ECV in relation to the change in erosion rate is studied for particle kinetic energies between 6 × 10-10 and 6 × 10-7 (using alumina particles of 3-29.2 μm and speeds between 75 and 200 m/s). The transition is not suddenly, but extends over at least one decade of kinetic energy. During this transition, the ECV slowly rises to a value >1. SEM pictures of the eroded surfaces accompany the measurements.