ResearchProject Area A
Subprojekt A1

Subprojekt A1 Non Destructive Characterization of Turbine Blades

The research program includes the development of non-destructive testing techniques such as high frequency eddy current testing, high frequency induction thermography, remote field eddy current testing and harmonic analysis of eddy current signals for local defect detection and classification, as well as material characterization in component multilayer systems of turbine engine components.

MOTIVATION AND OBJECTIVES

Coating characterization of a turbine blade using high frequency eddy current technology

High demands on the performance and reliability of modern engines require the integrity of highly stressed engine components such as turbine, compressor and fan blading and their condition assessment during inspections and maintenance. During operation, the blading is exposed to extremely high thermal, corrosive, erosive and mechanical stresses. The components are designed as a component multilayer system according to that stress profile. The base and layer material has to fulfil highest demands required for continuous engine operation. The condition and integrity of engine blading are of strategic importance for engine reliability and operation safety. This places a stringent requirements on non-destructive testing techniques, material characterization and early damage detection.  In order to be able to assess and evaluate a necessary repair requirements for stressed components and thus also be able to take these into account for the planning of the further regeneration path, a fast engine components investigation, which can already be carried out in the partially stripped engine, is becoming increasingly important.

Video: Blisk inspection using induction thermography

RESULTS

In the first funding period which was oriented on the particular base material and layer properties of turbine blades of the high-pressure turbine, basic research were carried out to map the test conditions via modeling. With the new development of a multi-parameter high-frequency eddy current technique and induction thermography with pulsed excitation in the megahertz range, a new field of application with regard to automated defect detection and classification, as well as material characterization of thin layer and component surface zones has been successfully developed on the example of highly-loaded turbine blades. Further areas of application are thin coatings on functional components, gliding surfaces or guides, as well as high-performance components with tight tolerances of surface zones in other capital goods.

Combined coating condition evaluation of the corrosion protection layer (KSS) and thermal barrier (WDS) using high frequency eddy current technology

The results of the second funding period describe non-destructive defect detection and material characterization in blade channel of turbine disc and blisk-type compressor with limited accessibility. Component testing and condition assessment of complex geometries was achieved by customizing the sensor and inductor properties. The determination of the damage depth in thick-walled components was realized by the new development of a remote field eddy current technique.

Defect detection in the blade channel (turbine blades) using high-frequency induction thermography with copper mirror

CURRENT WORKS AND OUTLOOK

The third funding period aims to to develop a mobile and flexible electromagnetic testing system with adapted eddy current sensors, as well as a thermographic testing system with combined inductor mirror optics for defect detection.  The purpose of the development is to evaluate the condition of stator and rotor blades directly at the partially stripped engine. Another subject of the research is the in situ detection and characterization of damage development as well as the changes in material properties under thermal and cyclic loading of regenerated samples and components compared to new parts. The changes in specimen are going to be investigated using a specially designed thermomechanical test rig with combined non-destructive testing techniques like eddy current, thermography and acoustic emission. The use of initially paramagnetic Ni-base materials at high temperatures in a sulfur-containing atmosphere (such as in the exhaust gas stream) leads to significant changes in the magnetic properties due to the local formation of ferromagnetic phases. In order to characterize, quantify and use as a condition indicator of the degree of high-temperature microstructural changes (hot gas corrosion) in turbine blade materials the development of a non-destructive electromagnetic testing technique based on harmonic analysis is planned.


PUBLICATIONS

  • Bruchwald, O.; Frackowiak, W.; Reimche, W.; Maier, H. J. (2016) Applications of High Frequency Eddy Current Technology for Material Characterization of Thin CoatingsIn: Journal of Materials Science and Engineering 2016 (6), S. 185–191
    DOI: 10.17265/2161-6213/2016.7-8.001
  • Schlobohm J.; Bruchwald, O.; Frackowiak, W.; Li, Y.; Kästner, M.; Pösch, A.; Reimche, W.; Reithmeier, E.; Maier, H. J. (2016) Turbine blade wear and damage – An overview of advanced characterization techniquesMaterials Testing 58 (5), S. 389–394
    DOI: 10.3139/120.110872
All publications of the Collaborative Research Centre

SUBPROJECT LEADER

Angie Faust
Office
Address
Appelstraße 9
30167 Hannover
Address
Appelstraße 9
30167 Hannover

STAFF

Non-public person