This document specifies the procedure for the determination of coating strength, and hence of cohesive strength in a tubular coating tensile test.
The test is intended to determine the tensile coating strength parallel to the spray layers (normal to the spray direction) and to identify differences in particle cohesion quality, as caused by defects as internal delamination at cracks or oxides between the spray particles or splats.
The tubular coating tensile test is suitable for sprayed coatings deposited using metallic materials (not carbides and ceramics).
The tubular coating tensile test is not suitable for fused sprayed coatings deposited using self-fluxing alloys.
The test supports quality assurance and is intended to be applied for the purpose of coating optimization by identifying the influences of coating parameters and spray materials on the coatings's quality. Furthermore, the coating in particular for cold sprayed coatings can be compared with the characteristics of similar solid materials and the coating's quality can be assessed.
This test is not recommended for thin coatings (coating thickness < 500 µm), since massive scattering of results is to be expected here. Due to the size of the specimen, it is particularly suitable to apply the tubular coating tensile test for coating processes that use a concentrated spray jet and a highly focused spray spot, as in the case of cold spraying, high velocity flame spraying (HVOF) or plasma spraying. Applying the tubular coating tensile test for coating processes that use a broad spray jet, such as flame spraying and arc spraying, may require special spraying measures, e.g. the use of a template to ensure a nearly vertical impingement angle.