Neutron diffraction was used to measure the residual strain field in plasma-sprayed zirconia thermal barrier coatings (TBCs). Data were collected at the British neutron spallation source of ISIS (Didcot), on ENGIN, a recently installed TOF (time-of-flight) instrument designed for residual strain depth profiling. Its particular geometry permitted a direct measurement of the interplanar distances of crystallographic planes lying parallel to the component surface as well as the measurement of zero-strain reference samples. The latter were annealed samples of the three present phases: zirconia (top coat), NiCoCrAlY (bondcoat), and copper (substrate). In this way epsilon(33), the strain component perpendicular to the sample surface, was determined at several positions inside the component, for all the present phases. The results of this analysis, consisting of a strain profile throughout the entire cross-section of the coated component, were integrated by those obtained by a destructive testing, performed after TOF data collection, consisting in the measurement of curvature change of the ceramic after substrate removal by chemical attack. (C) 1998 Elsevier Science S.A. All rights reserved.
Strain gradients in plasma-sprayed zirconia thermal barrier coatings
BERTINI, LEONARDO;
1998-01-01
Abstract
Neutron diffraction was used to measure the residual strain field in plasma-sprayed zirconia thermal barrier coatings (TBCs). Data were collected at the British neutron spallation source of ISIS (Didcot), on ENGIN, a recently installed TOF (time-of-flight) instrument designed for residual strain depth profiling. Its particular geometry permitted a direct measurement of the interplanar distances of crystallographic planes lying parallel to the component surface as well as the measurement of zero-strain reference samples. The latter were annealed samples of the three present phases: zirconia (top coat), NiCoCrAlY (bondcoat), and copper (substrate). In this way epsilon(33), the strain component perpendicular to the sample surface, was determined at several positions inside the component, for all the present phases. The results of this analysis, consisting of a strain profile throughout the entire cross-section of the coated component, were integrated by those obtained by a destructive testing, performed after TOF data collection, consisting in the measurement of curvature change of the ceramic after substrate removal by chemical attack. (C) 1998 Elsevier Science S.A. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
