Assessment of variations in thermal cycle life data of thermal barrier coated rods

The reported study had the purpose to examine variations in cyclic life and in adhesive/cohesive coating strength. Possible effects of heating rate, stress reversal, temperature level, and ceramic deposition methods on coating life were also investigated. Life cycle data for 22 thermal barrier coated rods were examined and found to be statistically modeled by normal or log-normal distributions. The sample mean was 1330 cycles with a standard deviation of 520 cycles. Adhesive/cohesive pulloff strength data for 20 thermal barrier coated flat head piston specimens were taken. The average pulloff stress was 9 MPa with a standard deviation of 4.2 MPa. It was found that variations in heating rate can produce significant variations in the life cycle data.