The Peel Adhesion Test for Metal-Ceramic Interfaces

Abstract

Although the peel test is used extensively in the adhesives industry for characterizing the adhesion strength, relative little attention has been paid to this method by ceramists. The purpose of this work is development of the peel adhesion test for determination of adhesion strength of ceramic coatings on metals, e.g. thermal sprayed coatings, using thin metallic foils as substrates. In contrast to many other methods of adhesion testing for metal-ceramic couples, the peel test assures separation of the two materials exactly along the interface. The plastic work consumed by the flexible metallic foil during the peel test can contribute significantly to the measured peel load. It is thus important to be able to quantify it in order be able to make inferences about the adherence of the interface. The energy balance during peeling of the metallic foils is proposed and analysed. An experimental method is proposed which verifies the energy balance and allows separation of the plastic work during peeling for a work hardening material, from the net work of adhesion. The prediction is compared to experimentally measured plastic work values for several materials. The predicted behaviour of metallic foils during peeling has been confirmed. The net peel adhesion strength has been determined for several model systems (metal - epoxy) as well as thermal sprayed ceramic coatings on metals. It is concluded the Peel Adhesion Test (PAT) is a unique and precise method for determination of bonding strength of metals to ceramics.