Microstructure and Phase Composition of Composite Coatings Formed by Plasma Spraying of ZrO2 and B4C Powders
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The effect of addition of 5 to 30 wt.% boron carbide (B4C) on structure and hardness of plasma sprayed zirconia (ZrO2) coating has been studied in this paper. The coatings have exhibited a uniform porous microstructure. A reaction between B4C and ZrO2 resulted in the formation of a diboride (ZrB2) phase. The presence of ZrB2 in the coatings has been confirmed through x-ray diffraction studies. In order to study the effect of critical processing parameters, the coatings have also been deposited under increased hydrogen flow rate (11.8 SLM). This increased the abrasion integrity of the coatings. A high yield of ZrB2 was observed in the case of 15 wt.% B4C addition. Hardness of the coatings have been influenced by the porosities, additionally generated by the formation of ZrB2. Under increased hydrogen flow rate, a composite coating of ZrO2-ZrB2 was obtained from the ZrO2-B4C powder mixture.
Keywordsboron carbide composite coatings plasma spray zirconia zirconium boride
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