Scope:

The test procedure in ASTM C1624 gives quantitative measurement of extrinsic adhesion strength and damage resistance of the coating-substrate changing as a function of the applied force. This test method is applicable to a large range of hard ceramic coating compositions like – nitrides, carbides, oxides and diamond like carbon structure on either ceramic or metallic surface.

Test Procedure:

The test method in ASTM C1624 uses a diamond stylus of predefined geometry, for drawing on the flat surface of a coated test specimen at a uniform speed. A predefined constant, or periodically increasing normal force is applied at a defined distance. The force level which produces a defined type of damage in the coating is defined as a critical scratch load. The test described in ASTM C1624 also elaborates on usage of tangential force and acoustic emission signals. This acts as a secondary test data to differentiate coating damage levels.

 Specimen size:

The test method in ASTM C1624 cannot use polymer coatings, ductile metal coatings which are very thin (<0.1 μm), or very thick (>30 μm). So it is perfect for ceramic coating in between thickness.

Data:

The value of thickness in ASTM C1624 is defined in terms of diamond stylus bearing 200 μm radius. These values range between 0.1 – 30 μm. The testing specimens often have planar geometry, while having cylindrical structure is also not uncommon. Also thinner coatings might require smaller diameter styluses and less normal forces.