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Microstructural and tribological comparison of HVOF-sprayed and post-treated M–Mo–Cr–Si (M = Co, Ni) alloy coatings

High velocity oxygen-fuel (HVOF)-sprayed wear resistant Co–28%Mo–17%Cr–3%Si and Ni–32%Mo–15%Cr–3%Si coatings, both as-sprayed and after heat treatments at 600 °C for 1 h, have been studied. Particularly, their dry sliding wear behaviour has been compared by ball-on-disk tests against different count...

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Bibliographic Details
Published in:Wear 2007-09, Vol.263 (7), p.1397-1416
Main Authors: Bolelli, Giovanni, Cannillo, Valeria, Lusvarghi, Luca, Montorsi, Monia, Mantini, Fabio Pighetti, Barletta, Massimiliano
Format: Article
Language:English
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Summary:High velocity oxygen-fuel (HVOF)-sprayed wear resistant Co–28%Mo–17%Cr–3%Si and Ni–32%Mo–15%Cr–3%Si coatings, both as-sprayed and after heat treatments at 600 °C for 1 h, have been studied. Particularly, their dry sliding wear behaviour has been compared by ball-on-disk tests against different counterbodies (100Cr6 steel and sintered alumina), and differences were discussed based on microstructural characteristics and micromechanical properties (Vickers microindentation and scratch test responses). As-sprayed coatings contain oxide stringers, are mostly amorphous and display rather low Vickers microhardness (about 7.4 GPa for the Co-based and 6.2 GPa for the Ni-based), toughness and elastic modulus. Heat-treated ones display sub-micrometric crystalline intermetallics, improving hardness (9.6 GPa and 7.4 GPa, respectively) and elastic modulus. Scratch tests indicate greater brittleness of the Ni-based alloy (higher tendency to cracking). Due to low hardness and toughness, both as-sprayed coatings undergo wear loss against steel and alumina counterparts. The more plastic Co-based alloy undergoes higher adhesive wear against steel and lower abrasive wear against alumina; the situation is reversed for the Ni-based alloy. After heat treatment, the wear loss against steel is very low for both coatings; abrasive wear still occurs against alumina.
ISSN:0043-1648
1873-2577
DOI:10.1016/j.wear.2006.12.002