Recombination of silica and zirconia into zircon by means of laser treatment of plasma-sprayed coatings

Abstract : Self-supported zircon (ZrSiO 4) coatings have been deposited by means of atmospheric pressure plasma spraying, a high growth rate deposition method. However, it is well known that ZrSiO 4 dissociates into ZrO 2 and SiO 2 in the high-temperature plasma torch during plasma spraying, the rapid quenching preventing reverse combination of both components into ZrSiO 4. Usually, high-temperature annealing (1,600–1,900 K) is applied to recombine SiO 2 and ZrO 2 into ZrSiO 4. In this contribution, we investigate an attractive technological alternative to recombine SiO 2 and ZrO 2 into ZrSiO 4 by laser treatment with a scanning continuous wave CO 2 laser. By carefully adjusting the CO 2 laser treatment parameters (laser power density and scanning velocity), we show that the SiO 2 and ZrO 2 phases indeed recombine into ZrSiO 4 , however, with a very low recombination rate. Thus, we have investigated the addition of SiO 2-rich glassy particles to the plasma spray powders to facilitate the recombination of ZrO 2 , and SiO 2 into ZrSiO 4 during the laser treatment. Furthermore, the beneficial role of the glassy particles addition to substantially lower the annealing temperature during classical heat treatments has been studied. Available evidence indicates that the glassy particles melt during heat treatment , and thus favor the mobility and availability of silica at the ZrO 2 grains, which results in a lowering of the reaction temperature and an enhancement of the reaction kinetics.
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Submitted on : Monday, March 14, 2016 - 10:14:39 AM
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Sabine Schelz, Franck Enguehard, Nadège Caron, Daniel Plessis, Benoît Minot, et al.. Recombination of silica and zirconia into zircon by means of laser treatment of plasma-sprayed coatings. Journal of Materials Science, Springer Verlag, 2008, 43, pp.1948-1957. ⟨10.1007/s10853-007-2406-z⟩. ⟨hal-01287440⟩

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