Damage assessment and life prediction of TBC systems

Abstract

Plasma vapour deposition technique is employed to determine the perspective of possible factors that initiates coating spallation when applied in service. Different simulated experiments are designed to bring out the effects of stress by either mechanical or thermal fluctuation associated with corrosion. Interfaces have been investigated to study coating spallation, when adhesion seemed to be key for evaluation. Elemental poisoning at interface by either thermal diffusion or embedded cation on pre-form surface or contamination from combustion product reduces the life of coating. Different changes upon elemental incorporation have shown that reactive element addition to bond coat alloy reduces poisoning effects by vacancy sink and elemental scavenges process. In service degradations are described to compare performances of uncoated, metallic coated and thermal barrier coated specimens. Sintering of ceramics on passage of time at temperature or at temperatures greater than stipulation and void formation at interface being associated with spinal formation are believed to be unrecoverable problems. Lives of combustion engines are solely dependent on thermal profile former. Liner is one of components under optimum combustion vibrations. The high temperature combustion vibrations within cooling air reaction quenches have been provided by free access of thermal expansion for liners. Fatigues of coated liners are interpreted by endurance limit obtained from isothermal and high cycle fluctuating stress fatigue tests. Thermal barrier coating on combustor liner is normally prepared by plasma spray technique. The designed performance has been dependent on coating performance. The non-destructive techniques of liner temperature evaluation during service and after every schedule of service also produce the information of ageing response of coated liner.