Adhesion or Cohesion Strength of Thermal Spray Coatings (ASTM C633)

作者:江苏天源    添加时间:2014/4/15 9:50:30    浏览量:

The ASTM C633 test method is used to determine the adhesion or cohesion strength of a thermal spray by subjecting it to tension perpendicular to the surface.

The substrate fixture that spray coating is applied to is most commonly a cylinder made of the same metal that would be used as the substrate of the coating in its actual use. If a substrate is not specified for your application, then the ASTM C633 standard specifies to use SAE 1018 or 1020 steel. This substrate cylinder's length must be no less than 1.5 in with parallel faces between 0.9 in (23 mm) -1.0 in (25 mm) diameter with one end threaded for attachment to the load fixture and the other end flat for application of the spray coating (Note: ASTM C633 specifies three standard thread sizes: 1/2”-20, 5/8”-18, or 3/4”-16). A similar, but uncoated fixture, is then glued to the surface of the coating with a suitable adhesive bonding agent. The adhesive bonding agent should not be the "weakest link", but should be at least as strong as the minimum required adhesion or cohesion strength of the coating.

To ensure the direction of force application is perpendicular to the coated surfaces, ASTM C633 specifies to use a self-aligning load fixture to attach these substrate cylinders to the test frame. In addition to this, we find it extremely useful to incorporate an axial slack coupling into the design of the loading fixture as it greatly improves setup time. The test speed must be constant and set between 0.030 in/min (0.013 mm/s) - 0.050 in/min (0.021 mm/s), and the load measurement accuracy should be within ± 1.0% of reading (as defined by the ASTM E4 standard).

When asked to provide a system for a thermal spray coating research and development application, we typically specify a Model 5969 frame (50 kN or 11,250 lbf capacity) with self-aligning load fixtures. While this capacity covers all known thermal spray coating adhesion strengths, some users prefer a higher capacity system for higher force applications in the future. We captured the required maximum load strength with our Bluehill® 3 Software and used it to calculate the adhesion/cohesion strength (or maximum load/cross-sectional area). If failure is entirely at the coating-substrate interface, then the result is referred to as the adhesion strength. If failure occurs within the coating, the result is referred to as the cohesion strength.

相关标准 ASTM C633
样品类型: 不适用
Materials: 粘结
测试类型: 拉伸
业务类型: 航空企业及供应商