University of Oulu

aolo Sassatelli, Giovanni Bolelli, Magdalena Lassinantti Gualtieri, Esa Heinonen, Mari Honkanen, Luca Lusvarghi, Tiziano Manfredini, Rinaldo Rigon, Minnamari Vippola, Properties of HVOF-sprayed Stellite-6 coatings, Surface and Coatings Technology, Volume 338, 2018, Pages 45-62, ISSN 0257-8972, https://doi.org/10.1016/j.surfcoat.2018.01.078

Properties of HVOF-sprayed Stellite-6 coatings

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Author: Sassatelli, Paolo1,2; Bolelli, Giovanni1; Lassinantti Gualtieri, Magdalena1;
Organizations: 1Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Via Pietro Vivarelli 10/1, 41125 Modena (MO), Italy
2Present address: Il Sentiero International Campus S.r.l., Via Friuli 11, 36015 Schio (VI), Italy
3Center of Microscopy and Nanotechnology, University of Oulu, P.O. Box 8000, 90014, Finland
4Materials Science, Tampere University of Technology, P.O. Box 589, 33101 Tampere, Finland
5Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Local Unit Università di Modena e Reggio Emilia, Via Pietro Vivarelli 10/1, 41125 Modena (MO), Italy
6Ecor Research S.p.A., Via Friuli 11, 36015 Schio (VI), Italy
Format: article
Version: accepted version
Access: embargoed
Persistent link: http://urn.fi/urn:nbn:fi-fe2018080733445
Language: English
Published: Elsevier, 2018
Publish Date: 2020-01-31
Description:

Abstract

Stellite-6 coatings were deposited onto AISI 304 stainless steel substrate by gas-fueled HVOF spraying, systematically varying the process parameter settings.

By operating the HVOF torch with a fuel-rich mixture, dense coatings (<1% porosity) are produced, containing up to ≈3 vol% oxide inclusions. A substantial amount of a Cr-rich f.c.c. phase is found, mainly produced by quenching of molten lamellae, and distinct from the equilibrium, Co-based f.c.c. solid solution retained in unmelted particles. These coatings exhibit pseudo-passive behavior and survive 5 cycles (100 h) of the Corrodkote test (ASTM B380-97) with no substrate corrosion. Coatings obtained from oxygen-rich mixtures, on the other hand, contain fewer oxide inclusions but also greater porosity, and do not protect the substrate against corrosion.

The wear behavior of the coatings is less influenced by deposition conditions. In ball-on-disk dry sliding tests, all coatings exhibit wear rates of 2–3 × 10⁻⁵ mm³/(N·m), higher than those reported for bulk or clad Stellite, because of interlamellar delamination. Strain-induced, “martensitic” phase transformation from the f.c.c. structure to a h.c.p. one is observed over a 1–2 μm depth below the contact surface. Additional tribo-oxidation is onset when frictional heat dissipation has heated the wear debris enough to trigger its reaction with the environment. Correspondingly, a transition to a regime of higher friction occurs (from ≈0.6 to ≈0.8). At 400 °C, lamellar delamination is suppressed but wear rates rise to 5–8 × 10⁻⁵ mm³/(N·m) because of abrasive and adhesive wear. At 800 °C, a dense “glaze” tribofilm is formed by sintered debris particles, firmly bonded to a thermally grown oxide scale on the underlying metal surface. The “glaze” protects the coating, lowering the wear rate to ≈1 × 10⁻⁵ mm³/(N·m) and the friction coefficient to <0.45. Under high-stress particle abrasion conditions, wear rates of ≈1 × 10⁻³ mm³/(N·m) are found.

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Series: Surface & coatings technology
ISSN: 0257-8972
ISSN-E: 1879-3347
ISSN-L: 0257-8972
Volume: 338
Pages: 45 - 62
DOI: 10.1016/j.surfcoat.2018.01.078
OADOI: https://oadoi.org/10.1016/j.surfcoat.2018.01.078
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Subjects:
Copyright information: © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
  https://creativecommons.org/licenses/by-nc-nd/4.0/