NiCrAlY layers containing different amounts of Al2O3 (0, 3, 6, 12, 18 wt.%) were deposited onto stainless steel substrates by a “hybrid” plasma spray process whereby the NiCrAlY powder was fed in dry form whilst fine Al2O3 powder, dispersed in ethanol, was injected through a suspension feeding system. The Al2O3 reinforcement, consisting of fine, rounded particles interspersed within larger NiCrAlY lamellae, only causes marginal changes in hardness, due to the limited particles-matrix cohesion. Nonetheless, at room temperature, ball-on-disk dry sliding wear rates against sintered Al2O3 counterparts decrease from ≈5⁎10−4 mm3/(Nm) for pure NiCrAlY to ≈5⁎10−6 mm3/(Nm) with 18 wt.% Al2O3 addition. Pure NiCrAlY indeed suffers adhesive wear, whereas, on the composite coatings, the pull-out of some Al2O3 particles triggers the formation of a tribo-layer of smeared oxide fragments, which mediates the contact with the counterbody. At 400 °C and at 700 °C, all wear rates are levelled to ≈8⁎10−5 mm3/(Nm) and ≈2⁎10−5 mm3/(Nm), respectively. An oxide layer grows on the NiCrAlY matrix upon high-temperature exposure, resulting in a tribo-oxidation wear mechanism, which makes the addition of Al2O3 irrelevant. At 700 °C, coatings are further strengthened by partial healing of interlamellar defects and by fine-grained β-NiAl precipitating within the metal matrix.

Tribology of NiCrAlY+Al2O3 composite coatings by plasma spraying with hybrid feeding of dry powder+suspension / Bolelli, Giovanni; Candeli, Alessia; Lusvarghi, Luca; Ravaux, A.; Cazes, K.; Denoirjean, A.; Valette, S.; Chazelas, C.; Meillot, E.; Bianchi, L.. - In: WEAR. - ISSN 0043-1648. - ELETTRONICO. - 344-345:(2015), pp. 69-85. [10.1016/j.wear.2015.10.014]

Tribology of NiCrAlY+Al2O3 composite coatings by plasma spraying with hybrid feeding of dry powder+suspension

BOLELLI, Giovanni;CANDELI, ALESSIA;LUSVARGHI, Luca;
2015

Abstract

NiCrAlY layers containing different amounts of Al2O3 (0, 3, 6, 12, 18 wt.%) were deposited onto stainless steel substrates by a “hybrid” plasma spray process whereby the NiCrAlY powder was fed in dry form whilst fine Al2O3 powder, dispersed in ethanol, was injected through a suspension feeding system. The Al2O3 reinforcement, consisting of fine, rounded particles interspersed within larger NiCrAlY lamellae, only causes marginal changes in hardness, due to the limited particles-matrix cohesion. Nonetheless, at room temperature, ball-on-disk dry sliding wear rates against sintered Al2O3 counterparts decrease from ≈5⁎10−4 mm3/(Nm) for pure NiCrAlY to ≈5⁎10−6 mm3/(Nm) with 18 wt.% Al2O3 addition. Pure NiCrAlY indeed suffers adhesive wear, whereas, on the composite coatings, the pull-out of some Al2O3 particles triggers the formation of a tribo-layer of smeared oxide fragments, which mediates the contact with the counterbody. At 400 °C and at 700 °C, all wear rates are levelled to ≈8⁎10−5 mm3/(Nm) and ≈2⁎10−5 mm3/(Nm), respectively. An oxide layer grows on the NiCrAlY matrix upon high-temperature exposure, resulting in a tribo-oxidation wear mechanism, which makes the addition of Al2O3 irrelevant. At 700 °C, coatings are further strengthened by partial healing of interlamellar defects and by fine-grained β-NiAl precipitating within the metal matrix.
2015
344-345
69
85
Tribology of NiCrAlY+Al2O3 composite coatings by plasma spraying with hybrid feeding of dry powder+suspension / Bolelli, Giovanni; Candeli, Alessia; Lusvarghi, Luca; Ravaux, A.; Cazes, K.; Denoirjean, A.; Valette, S.; Chazelas, C.; Meillot, E.; Bianchi, L.. - In: WEAR. - ISSN 0043-1648. - ELETTRONICO. - 344-345:(2015), pp. 69-85. [10.1016/j.wear.2015.10.014]
Bolelli, Giovanni; Candeli, Alessia; Lusvarghi, Luca; Ravaux, A.; Cazes, K.; Denoirjean, A.; Valette, S.; Chazelas, C.; Meillot, E.; Bianchi, L....espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11380/1073695
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