Failure Mechanisms Investigation in Thermal Barrier Coatings under Isothermal and Non-sothermal Fatigue Loadings using Design of Experiments

Document Type: Persian

Authors

1 Assistant Professor, Department of Mechanical Engineering, University of Semnan, Semnan, Iran

2 Professor, Department of Mechanical Engineering, Sharif University, Tehran, Iran.

Abstract

In this article, failure and fracture mechanisms in an aluminum alloy (which has been used in diesel internal combustion engines), with and without ceramic thermal barrier coatings, have been investigated under isothermal and non-isothermal fatigue loadings. In this research, the base material is an aluminum-silicon-magnesium alloy and the thermal barrier coating includes a metallic bond coat layer with 150 µm thickness and a top coat layer, made of zirconia stabilized 8%wt. yttria with 350 µm thickness, which is applied on the substrate by the plasma thermal spray method. In order to study the failure and the sensitivity analysis, isothermal fatigue tests (or low-cycle fatigue tests at constant temperatures) and non-isothermal fatigue tests (or out-of-phase thermo-mechanical fatigue tests) were performed on test specimens. Then, fracture mechanisms in the aluminum alloy, were investigated by the scanning electron microscopy. After checking the fatigue damage and the failure analysis, the sensitivity of the material lifetime was studied based on different parameters (the temperature and the strain). Based on obtained results, the fracture surface of the aluminum alloy had dimples and therefore, its fracture was ductile. In thermal barrier coating, the damage mechanism was the separation between the substrate and the bond coat layer. The highest sensitivity was related to the strain parameter in fatigue tests of the aluminum alloy (with and without coating).

Keywords


[1] Azadi M, Thermo-mechanical fatigue life prediction model for aluminum alloy with thermal barrier coating, PhD Thesis, Sharif University of Technology, Tehran, Iran, 2013.

[2] Tzimas E, Muellejans H, Peteves SD, Bressers J, Stamm JW, Failure of thermal barrier coating under cyclic thermo-mechanical loading, Acta Materialia, vol. 48, 2000, pp. 4699-4707.

[3] Peichl A, Beck T, Voehringer O, Behavior of an EB-PVD thermal barrier coating system under thermo-mechanical fatigue loading, Surface and Coating Technology, vol. 162, 2003, pp. 113-118.

[4] Jinnertrand M, Brodin H, Crack initiation and propagation in air plasma sprayed thermal barrier coatings, testing and mathematical modeling of low cycle fatigue behavior, Materials Science and Engineering A, vol. A379, 2004, pp. 45-57.

[5] Aguero A, Muelas R, Gutierrez M, Vulpen RV, Osgerby S, Banks JP, Cyclic oxidation and mechanical behavior of slurry aluminide coatings for steam turbine components, Surface and Coatings Technology, vol. 201, 2007, pp. 6253-6260.

[6] Uzun A, Cevik I, Akcil M, Effects of thermal barrier coating on a turbocharged diesel engine performance, Surface and Coatings Technology, vol. 116-119, 1999, pp. 505-507.

[7] Ranjbar-far M, Absi J, Mariaux G, Dubois F, Simulation of the effect of material properties and interface roughness on the stress distribution in thermal barrier coatings using finite element method, Materials and Design, vol. 31, 2010, pp. 772-781.

 

[8] Bartsch M, Baufeld B, Dalkilic S, Chernova L, Heinzelmann M, Fatigue cracks in a thermal barrier coating system on a super-alloy in multi-axial thermo-mechanical testing, International Journal of Fatigue, vol. 30, 2008, pp. 211-218.

[9] Beck T, Henne I, Loehe D, Lifetime of cast AlSi6Cu4 under superimposed thermal-mechanical fatigue and high-cycle fatigue loading, Materials Science and Engineering A, vol. A483-484, 2008, pp. 382-386.

[10] Takahashi T, Sasaki K, Low cycle thermal fatigue of aluminum alloy cylinder head in consideration of changing metrology microstructure, Procedia Engineering, vol. 2, 2010, pp. 767-776.

[11] Wright PK, Influence of cyclic strain on life of a PVD TBC, Materials Science and Engineering A, vol. A245, 1998, pp. 191-200.

[12] Rahmani K, Nategh S, Influence of aluminide diffusion coating on low cycle fatigue properties of Rene80, Materials Science and Engineering A, vol. A486, 2008, pp. 686-695.

[13] Sahu JK, Das Dk, Nandy TK, Mandal D, Rajinikanth V, Swaminathan J, Ray AK, Effect of titanium aluminide coating on cyclic plastic deformation and fatigue life of a titanium alloy at 600°C, Materials Science and Engineering A, vol. 530, 2011, pp. 664-668.

[14] Azadi M, Moridi A, Farrahi GH, Optimal experiment design for plasma spray parameters at bending loads, International Journal of Surface Science and Engineering, vol. 6(1-2), 2012, pp. 3-14

[15] Azadi M, Farrahi GH, Moridi A, Optimization of air plasma sprayed thermal barrier coating parameters in diesel engine applications, Journal of Materials Engineering and Performance, vol. 22(11), 2013, pp. 3530-3538

[16] Azadi M, Analysis and improvement of a passenger car NVH behavior using DOE method, MSc Thesis, K.N. Toosi University of Technology, Tehran, Iran, 2008.

[17] ASM Handbook, Mechanical Testing and Evaluation, ASM International, 2000

[18] Shi J, Karlsson AM, Baufeld B, Bartsch M, Evaluation of surface morphology of thermo-mechanically cycled NiCoCrAlY bond coats, Materials Science and Engineering A, vol. A434, 2006, pp. 39-52.

[19] Moridi A, Azadi M, Farrahi GH, Thermo-mechanical stress analysis of thermal barrier coating system considering thickness and roughness effect, Surface and Coatings Technology, vol. 243, 2014, pp. 91-99.