Young' s modulus and interface fracture toughness of metal-base ceramic coatings

The Young' s modulus is a specially important material parameter, which is often used in the fracture mechanics study on coating/substitute interface strength. A new two-side coated specimen in 3-point bend test was proposed based on compound beam theory. The Young' s modulus of metal-base ceramic coating was measured through the two-side coated specimen and through the single-side coated specimen. The test results show the Young' s modulus increases with rise of coating thickness. On one hand, the thicker the coating is, the more accurate the result is.On the other hand, inctrase of coating thickness results in the reduction of porosity, which makes the Young' s modulus increase.If was found that the spraying orientation has effect on Young' s modulus of coating which takes on the anisotropic property. In addition, interface fracture toughness was also introduced, which mainly include the 4-point bend test to measure interface critical strain energy rate, improved tensile test and local approach based on Weibull criterion.