Abstract
ABSTRACTA continuous microindentation apparatus was constructed with a maximum load capacity of 45 N (resolution of 0.1 N) and with a maximum displacement of 500 μm (resolution of 2.0 μm) and used to test bulk materials (brass, aluminum, steel, soda-lime glass and PMMA) and epoxy coatings on substrates of aluminum, steel, soda-lime glass and PMMA. The hardness (H) was determined with a Vickers indenter and compared to that obtained with a Tukon hardness tester. The elastic modulus of the coated systems was also estimated from the unloading curves. In general, we found that the indentation behavior of the epoxy coated system was influenced by the substrate with softer substrates (as with PMMA) being deformed before the indenter penetrates the coating. With all coated systems, the on-load value of H was independent of the penetration depth until the indenter penetrated the substrate. For the aluminum, steel and soda-lime glass substrates, the value of H after penetration increased slowly due to the pile up of the epoxy coating underneath the indenter supporting more of the load. For the PMMA substrate, hardness decreased after penetration because the hardness of PMMA was less than the epoxy coating.
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