Modulus Testing of Ceramic Coating
Innovative Test Solutions, Inc. has the capability of testing parts that experience very low loads in service, such as ceramic coatings used as a thermal barrier (TBC) on various internal components found in land based turbines and aircraft engine.
In the pursuit of constant improvement to maximize the operational efficiencies in turbines, ceramic coatings have become a critical component in today's stationary and aerospace gas turbines. Ceramic coatings are placed on a substrate (base material) on top of a bond coat (metallic based primer) to act as a thermal insulator to the part being coated, thus allowing for significantly higher inlet temperatures using standard super-alloys. The addition of such coatings leaves the components with a stack up of differing material characteristics, such as the elastic modulus, bend strength, and thermal lifting (coating spallation). These characteristics are evaluated using free standing modulus testing to acquire the ceramic modulus and bend strength.
ITS can accept sample sizes of a 1 in x 2 in panel or a 1 in round button. Samples are cut into ¼ inch strips with a diamond saw yielding three test points per sample to average any localized inconsistencies in the coating. Samples are then immersed in an acid etch to remove the bond coat from the base material which releases the ceramic coating. The specimens are then 3-point bend tested which provides the bend strength and young’s modulus of the ceramic coating.
With the installation of different rated load cells, this frame range is extended from ounces of force to a maximum of 1000 lbs of force. Through the use of a computer and custom written software by ITS, digital data is recorded and analyzed automatically, greatly improving testing accuracy. The same frame can be equipped with a PID controlled convection oven capable of temperatures up to 600°F (315°C).