Integrated Smart Materials Group

Thick overlay coatings are essential in protecting key components of jet engines and power plants from hot and harsh environments. Examples include thermal barrier coatings to protect combustors and blades, cermet coatings for abrasion and erosion resistance, and abradable coatings to control the clearance between rotating blades and the casing. This group conducts research to improve the protection capability of such coatings for materials developed in the High Temperature Materials Unit from both materials and processing perspectives.

Specialized Research Field

1. Warm Spray: a novel coating process

Thermal spray is the most widely used and fairly versatile process to deposit thick overlay coatings, in which the raw materials tend to be degraded as they are melted and projected toward the substrates due to oxidation, for example, in the air atmosphere and a notable amount of pores are generally included. We have developed a novel spray process based on high-velocity impact of solid powder particles in a thermally softened state and named it as "Warm Spray". We have demonstrated the capability of the process by depositing highly dense coatings of titanium and WC-Co with little degradation in the air.

"Fig. Principle of Warm Spray process." Image

Fig. Principle of Warm Spray process.


"Fig. Cross sectional TEM image of warm sprayed Titanium particle on Aluminum substrate with FEM analysis result" Image

Fig. Cross sectional TEM image of warm sprayed Titanium particle on Aluminum substrate with FEM analysis result


"Fig. Comparison of the microstructure and properties of WC-Co cermet coatings deposited by conventional HVOF spray and Warm Spray methods. Warm sprayed coating exhibits finer and uniform microstructure resulting in higher hardness and smoothness." Image

Fig. Comparison of the microstructure and properties of WC-Co cermet coatings deposited by conventional HVOF spray and Warm Spray methods. Warm sprayed coating exhibits finer and uniform microstructure resulting in higher hardness and smoothness.




2. Process analysis and modeling

Even with the same raw material and same process, resultant coatings can have widely different microstructures and properties. Due to the unique nature of the deposition process, the process-structure-property relationships of sprayed coatings are not fully established. We have been accumulating data and knowledge at various scales starting from impact of single sprayed particle, internal structure of single splat, AE measurement during deposition as well as the in-situ measurements of strains and stresses during spraying. Through developing these analysis and instrumentation with various collaborators, we aim to facilitate fundamental understanding of thermal spray processes and improve their reliability.

"Fig. Fundamental research on processing of thermal barrier coatings (TBC) covering from single particle impact to macroscopic coating deposition." Image

Fig. Fundamental research on processing of thermal barrier coatings (TBC) covering from single particle impact to macroscopic coating deposition.




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1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, JAPAN
E-Mail: KURODA.Seijinims.go.jp
National Institute for Materials Science (NIMS)
1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, JAPAN
TEL.+81-(0)-29-859-2000
FAX.+81-(0)-29-859-2029