Measurement of interface strength by the modified laser spallation technique. II. Applications to metal/ceramic interfaces

Abstract

Part II of this series presents applications of the modified laser spallation technique to several interface systems. For metal/pyrolytic graphite (PG) interfaces, the tensile strength of interfaces between 3-μm-thick coatings of Sn, Sb, Cu, Nb, Al, and Cr on a PG substrate were measured in units of MPa to be 18.53, 5.99, 15.46, 41.16, 16.53, and 15.47, respectively. It was found that the interface fracture mechanisms depend on the elastic-plastic properties of the coatings, but are independent of the interface strength. Interface strength between diamond, SnO2, and Nb coatings on polycrystalline alumina substrates were measured to be ≳140, 320, and 280 MPa, respectively. It is shown that the brittle fracture takes place at the interface upon spalling even if the plastic deformation exists within the coatings.