Interface indentation test for the determination of adhesive properties of thermal sprayed coatings

摘要

One of the most important limitations to the use of coated materials is the adhesion of the coating to its substrate. Indentation fracture has gained widespread acceptance as a means to determine the toughness of brittle materials [1,2]. More recently, attempts have been made to transpose this test to coating and substrate couples in order to produce and measure a mechanically stable crack in the coating and substrate interface. For thin coatings, indentation is generally performed on the surface of the sample [3-5], whereas for thick coatings, indentation into a cross-section either near the interface [6] or precisely at the interface [7, 8] has been proposed. According to Rickerby [9], an ideal adhesion test should be non-destructive, adaptable to routine testing of geometrically complex shapes, relatively simple to perform and interpret, amenable to standardization and automation, quantitative and reproducible, and directly related to coating reliability in specific applications. To date, no test fulfils all these considerations and all the commonly used tests are destructive. Nevertheless, among the several methods which produce a delamination of the coating, the indentation test at the interface seems to offer interesting prospects. So we choose to use this latter method to compare cracking resistances at the interface of substrates and coatings. The thermal spraying method consists of melting.