Abstract: Solid particle erosion of the CaLa₂S₄ infra-red transmitting material has been studied; it includes crack initiation and propagation, flake formation and oscillation as well as the effect of solid velocity (from 22 to 180m·s^-1) on crater morphology and erosion rate. Theoretical analysis has been carried out upon (1) plasticity in the contact zone, and (2) the striation mark on the lateral crack surface. And by using a membrane free vibration model, the widths of striation mark have been estimated.

Key words: solid particle erosion, infra-red transmitting material, impact fracture