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2652 |
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Study of plasma sprayed mullite coating using mullite and a mixture of alumina and silica powders as initial powder particles |
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Hamidreza Salimijazi* / Isfahan University of Technology, Iran Mahdi Hosseini/ Department of Materials Engineering, Isfahan University of Technology, Iran Larry Pershin/ Centre for Advanced Coating Technologies, University of Toronto, Canada, Canada Javad Mostaghimi/ Centre for Advanced Coating Technologies, University of Toronto, Canada, Canada Tom Coyle/ Centre for Advanced Coating Technologies, University of Toronto, Canada, Canada Hamed Samadi/ Centre for Advanced Coating Technologies, University of Toronto, Canada, Canada Ali Shafiei/ Department of Materials Engineering, Isfahan University of Technology, Iran |
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Plasma sprayed ceramic coatings are widely used for thermal barrier coating applications. Commercially available mullite powder particles and a mixture of mechanically alloyed alumina and silica powder particles were used to deposit mullite ceramic coatings by plasma spraying process. The coatings were deposited at three different substrate temperatures (room temperature, 300C, and 600C) on stainless steel substrates. Microstructure and morphology of both powder particles as well as coatings were investigated by using scanning electron microscopy (SEM). Phase formation and degree of crystallization of coatings were analyzed and estimated by using X-ray diffraction technique. Differential thermal analysis (DTA) method was used to study the phase transformation of coatings. Results indicated that the porosity level in the coating deposited using mullite initial powder particles was lower than that deposited using the mixed initial powder particles. The crystallization degree of the coating deposited using the mixed powder particles are higher than that deposited using mullite powder particles. DTA curves of coatings deposited using the mixed powders have showed some phase transformation due to crystallization of the retained amorphous phases such as mullite and alumina in the coatings. The degree of crystallization of the as sprayed coatings using the mixed powder particles was significantly increased after post deposition heat treatments. Results showed that the mechanically alloyed mixed powder can be used as initial powder particles for deposition of mullite coatings instead of using mullite powders. |