Property Measurements of Thin Coatings

Abstract

Colour and microhardness were the main two properties of thin coatings studied. The thinner the coatings, the more difficult it is to measure the properties of thin coatings (including thickness). The factors that influence the colour of thin coatings were examined. Yellow gold was deposited on white metal substrates by vacuum deposition and electrodeposition. Colour was measured using spectrophotometric techniques. CIE chromaticity co-ordinates were calculated from spectrophotometric data using a computer programme written for the purpose. The minimum thickness of coating required to produce its fixed colour and completely hide the underlying substrate was measured and found to depend on the nature of the substrate and coating, the method of applying the coating and the application operating conditions. The second part of the thesis covers the measurement of microhardness. A new technique was developed for the production of tungsten microindenters with tips between 0.1um and 1.0um diameter. The tips were formed by electromachining tungsten wire in an electropolishing solution controlled electronically to avoid etching. An instrument was developed using the microindenters for determining the microhardness of surfaces within the specimen chamber of a scanning electron microscope. Preliminary results were compared with those of conventional microhardness testing in air.