Multiobjective Optimization of Atmospheric Plasma Spray Process Parameters to Deposit Yttria-Stabilized Zirconia Coating
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JTTEE5 20:590–607 DOI: 10.1007/s11666-010-9604-y 1059-9630/$19.00 ASM International
Multiobjective Optimization of Atmospheric Plasma Spray Process Parameters to Deposit Yttria-Stabilized Zirconia Coatings Using Response Surface Methodology C.S. Ramachandran, V. Balasubramanian, and P.V. Ananthapadmanabhan (Submitted July 5, 2010; in revised form September 29, 2010) Atmospheric plasma spraying is used extensively to make Thermal Barrier Coatings of 7-8% yttriastabilized zirconia powders. The main problem faced in the manufacture of yttria-stabilized zirconia coatings by the atmospheric plasma spraying process is the selection of the optimum combination of input variables for achieving the required qualities of coating. This problem can be solved by the development of empirical relationships between the process parameters (input power, primary gas flow rate, stand-off distance, powder feed rate, and carrier gas flow rate) and the coating quality characteristics (deposition efficiency, tensile bond strength, lap shear bond strength, porosity, and hardness) through effective and strategic planning and the execution of experiments by response surface methodology. This article highlights the use of response surface methodology by designing a five-factor fivelevel central composite rotatable design matrix with full replication for planning, conduction, execution, and development of empirical relationships. Further, response surface methodology was used for the selection of optimum process parameters to achieve desired quality of yttria-stabilized zirconia coating deposits.
Keywords
atmospheric plasma spraying, optimization, response surface methodology, thermal barrier coatings, yttria-stabilized zirconia
1. Introduction Plasma-sprayed yttria-stabilized zirconia (YSZ) coatings are being increasingly used as thermal barrier coatings (TBCs) for gas turbines and diesel engines (Ref 1). Effective TBCs should exhibit low thermal diffusivity, strong adherence to the substrate, phase stability, and thermal shock resistance during thermal cycling, and provide oxidation and corrosion protection to both the metallic bond coat and the substrate. Many studies have contributed to a better understanding of the metallographic preparation, microstructure, thermal conductivity and diffusivity, residual stresses, and failure mechanisms of the YSZ coatings (Ref 2-6). The impacts of the plasma spray process parameters on the coating characteristics
C.S. Ramachandran and V. Balasubramanian, Department of Manufacturing Engineering, Annamalai University, Annamalai Nagar 608 002, Tamilnadu, India; and P.V. Ananthapadmanabhan, Plasma Spray Technologies Section (PSTS), Laser and Plasma Technology Division (L&PTD), Bhabha Atomic Research Centre (BARC), Anu Shakthi Nagar, Trombay, Mumbai 400 085, Maharashtra, India. Contact e-mail: [email protected].
590—Volume 20(3) March 2011
and properties have generally been studied by means of classical one-factor-at-a-time or empirical approaches. Plasma spraying, however, involves many parameters
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