ASTM International

Standard Test Method for Adhesion Strength and Mechanical Failure Modes of Ceramic Coatings by Quantitative Single Point Scratch Testing
 N C1624

Annotation

This test method covers the determination of the practical adhesion strength and mechanical failure modes of hard (Vickers Hardness HV = 5 GPa or higher), thin (#30 m) ceramic coatings on metal and ceramic substrates at ambient temperatures. These ceramic coatings are commonly used for wear/abrasion resistance, oxidation protection, and functional (optical, magnetic, electronic, biological) performance improvement.

In the test method, a diamond stylus of defined geometry (Rockwell C, a conical diamond indenter with an included angle of 120° and a spherical tip radius of 200 m) is drawn across the flat surface of a coated test specimen at a constant speed and a defined normal force (constant or progressively increasing) for a defined distance. The damage along the scratch track is microscopically assessed as a function of the applied force. Specific levels of progressive damage are associated with increasing normal stylus forces. The force level(s) which produce a specific type/level of damage in the coating are defined as a critical scratch load(s). The test method also describes the use of tangential force and acoustic emission signals as secondary test data to identify different coating damage levels.

Applicability to Coatings—This test method is applicable to a wide range of hard ceramic coating compositions: carbides, nitrides, oxides, diamond, and diamond-like carbon on ceramic and metal substrates. The test method, as defined with the 200 m radius diamond stylus, is commonly used for coating thicknesses in the range of 0.1 to 30 m. Test specimens generally have a planar surface for testing, but cylinder geometries can also be tested with an appropriate fixture.

Principal Limitations: