Application of coating technique to crack measurement at elevated temperature

The development of a new experimental method is required to observe the growth behavior of fatigue cracks easily even at elevated temperature. To satisfy the requirement, coating technique was introduced to fatigue testing at elevated temperature. the CT specimen surface was coated by TiAlN in order to prevent oxidation. The test material was a 1Cr-1Mo-0.25V steel. Crack length was measured during testing as well as after testing. At first, Crack length was determined using remote measurement system by operator's discrimination while the cyclic loading was interrupted. After testing, crack length was determined by 'Autocrack' software which was developed by ourseves. The ceramic coating layer itself had little influence on fatigue crack propagation.