Sand impact testing of durable coating on FLIR ZnS relevant to theLANTIRN E-O system window

Ewan M. Waddell; Desmond R. Gibson; J. Meredith

doi:10.1117/12.187377

28 September 1994 Sand impact testing of durable coating on FLIR ZnS relevant to theLANTIRN E-O system window

Ewan M. Waddell, Desmond R. Gibson, J. Meredith

Proceedings Volume 2286, Window and Dome Technologies and Materials IV; (1994) https://doi.org/10.1117/12.187377
Event: SPIE's 1994 International Symposium on Optics, Imaging, and Instrumentation, 1994, San Diego, CA, United States

Abstract

Measurements of the influence of sand/dust impact erosion on FLIR ZnS, coated with a range of durable coatings, have been made using spectral transmission. This activity has been carried out as part of a program to identify a sand/dust and rain erosion protective coating, for use on the Martin Marietta LANTIRN E-O system front element ZnS/ZnSe laminate window. Assessments have been carried out against MIL STD 810E sand/dust erosion specification, using the Defence Nuclear Agency sand erosion facility. A range of sand particle diameters (< 38 to 177 micrometers ), and velocities 45 to 206 m/s), has been investigated. Three anti- reflective durable coatings have been tested: thorium fluoride, diamond like carbon (DLC -- supplied from three separate vendors), and boron phosphide (BP) overcoated with DLC. BP/DLC showed no significant erosion damage or change in transmission for the range of test conditions, while DLC and ThF₄ exhibited significant erosion damage and consequent transmission reduction. A basic theory of solid particle impact is used to model transmission reduction in relation to coating hardness, velocity, and size of impacting sand particles. The concept of `erosion parameter and threshold velocity' is introduced, which provides a means of predicting transmission reduction for a range of sand erosion conditions.

Citation Download Citation

Ewan M. Waddell, Desmond R. Gibson, and J. Meredith "Sand impact testing of durable coating on FLIR ZnS relevant to theLANTIRN E-O system window", Proc. SPIE 2286, Window and Dome Technologies and Materials IV, (28 September 1994); https://doi.org/10.1117/12.187377

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