Research Papers: Gas Turbines: Structures and Dynamics

A Viscoplastic Modeling Approach for MCrAlY Protective Coatings for Gas Turbine Applications

[+] Author and Article Information
Roland Mücke

 Alstom, Brown Boveri Strasse 7, CH-5401 Baden, Switzerland

J. Eng. Gas Turbines Power 131(6), 062501 (Jul 14, 2009) (7 pages) doi:10.1115/1.3094032 History: Received October 15, 2008; Revised October 16, 2008; Published July 14, 2009

MCrAlY coatings are applied in industrial gas turbines and aircraft engines to protect surfaces of hot gas exposed components from oxidation and corrosion at elevated temperature. Apart from oxidation resistance, coatings have to withstand cracking caused by cyclic deformation since coating cracks might propagate into the substrate material and thus limit the lifetime of the parts. In this context, the prediction of the coating maximum stress and the strain range during cyclic loading is important for the lifetime analysis of coated components. Analyzing the state of stress in the coating requires the application of viscoplastic material models. A coupled full-scale cyclic analysis of substrate and coating, however, is very expensive because of the different flow characteristics of both materials. Therefore, this paper proposes an uncoupled modeling approach, which consists of a full-scale cyclic analysis of the component without coating and a fast postprocessing procedure based on a node-by-node integration of the coating constitutive model. This paper presents different aspects of the coating viscoplastic behavior and their computational modeling. The uncoupled analysis is explained in detail and a validation of the procedure is addressed. Finally, the application of the uncoupled modeling approach to a coated turbine blade exposed to a complex engine start-up and shut-down procedure is shown. Throughout the paper bold symbols denote tensors and vectors, e.g., σ stands for the stress tensor with the components σij. The superscripts (.)S and (.)C symbolize the substrate and the coating, respectively, e.g., εthS stands for the tensor of substrate thermal strain. Further symbols are explained in the text.

Copyright © 2009 by American Institute of Physics
Your Session has timed out. Please sign back in to continue.



Grahic Jump Location
Figure 1

Virgin substrate/MCrAlY-coating system

Grahic Jump Location
Figure 10

Absolute difference in mechanical strain between coupled and uncoupled modeling approaches

Grahic Jump Location
Figure 11

History of substrate metal temperature and mechanical strain for different engine start-up and shut-down operation concepts (only one cycle is shown)

Grahic Jump Location
Figure 12

Stress-strain response of the coating for different engine start-up and shut-down operation concepts

Grahic Jump Location
Figure 2

MCrAlY coating after service: (left) coating layer intact and aluminum resource exhausted; (right) coating TMF cracks not propagating into the substrate

Grahic Jump Location
Figure 3

Definition of cycle types

Grahic Jump Location
Figure 4

Measured stress temperature response of a MCrAlY coating subjected to an OP TMF cycle (7)

Grahic Jump Location
Figure 5

Temperature dependence of yield strength and rupture strain of MCrAlY coatings (7)

Grahic Jump Location
Figure 6

Type of material tests for parameter identification

Grahic Jump Location
Figure 7

Simulation of coating and substrate subjected to TMF OP cycles with different loading rates

Grahic Jump Location
Figure 8

Coated turbine component and mesh details

Grahic Jump Location
Figure 9

Stress-strain results using the coupled modeling approach (substrate at position A and coating at position B) and the uncoupled approach (coating at position B)



Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In