The grain size effect on the empirically determined erosion resistance of CVD-ZnS

Mechanical properties are important for infrared (IR) windows that may suffer from erosion damage during service. Zinc sulfide is a typical IR material that provides high transparency and satisfactory mechanical properties. Chemical vapor deposition, capable of producing large, complex shaped deposits with high purity, density, is commonly used to deposit IR materials. The substrate temperature determines the grain size of the deposits, the transparency and the mechanical properties. The substrate temperature is therefore vitally important to producing a quality deposition. Reports on the hardness and fracture toughness of the CVD-ZnS were found without empirical erosion tests, which give rise to a study on the effect of grain size on the actual solid particle erosion rate. This study evaluates the solid particle impingement of ZnS with different grain sizes, deposited at different substrate temperatures. The relationship between the mechanical properties and grain size is discussed.