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 × 10−5mm3/(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 × 10−5mm3/(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 × 10−5mm3/(N·m) and the friction coefficient to <0.45. Under high-stress particle abrasion conditions, wear rates of ≈1 × 10−3mm3/(N·m) are found.

Properties of HVOF-sprayed Stellite-6 coatings / Sassatelli, Paolo; Bolelli, Giovanni; Lassinantti Gualtieri, Magdalena; Heinonen, Esa; Honkanen, Mari; Lusvarghi, Luca; Manfredini, Tiziano; Rigon, Rinaldo; Vippola, Minnamari. - In: SURFACE & COATINGS TECHNOLOGY. - ISSN 0257-8972. - 338:(2018), pp. 45-62. [10.1016/j.surfcoat.2018.01.078]

Properties of HVOF-sprayed Stellite-6 coatings

Sassatelli, Paolo;Bolelli, Giovanni;Lassinantti Gualtieri, Magdalena;Lusvarghi, Luca;Manfredini, Tiziano;Rigon, Rinaldo;
2018

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 × 10−5mm3/(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 × 10−5mm3/(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 × 10−5mm3/(N·m) and the friction coefficient to <0.45. Under high-stress particle abrasion conditions, wear rates of ≈1 × 10−3mm3/(N·m) are found.
2018
338
45
62
Properties of HVOF-sprayed Stellite-6 coatings / Sassatelli, Paolo; Bolelli, Giovanni; Lassinantti Gualtieri, Magdalena; Heinonen, Esa; Honkanen, Mari; Lusvarghi, Luca; Manfredini, Tiziano; Rigon, Rinaldo; Vippola, Minnamari. - In: SURFACE & COATINGS TECHNOLOGY. - ISSN 0257-8972. - 338:(2018), pp. 45-62. [10.1016/j.surfcoat.2018.01.078]
Sassatelli, Paolo; Bolelli, Giovanni; Lassinantti Gualtieri, Magdalena; Heinonen, Esa; Honkanen, Mari; Lusvarghi, Luca; Manfredini, Tiziano; Rigon, Rinaldo; Vippola, Minnamari
File in questo prodotto:
File Dimensione Formato  
PRE PRINT_Properties of HVOF-sprayed Stellite-6 coating.pdf

Open access

Tipologia: Versione originale dell'autore proposta per la pubblicazione
Dimensione 1.87 MB
Formato Adobe PDF
1.87 MB Adobe PDF Visualizza/Apri
VOR_Properties of HVOF-sprayed Stellite-6 coating.pdf

Accesso riservato

Tipologia: Versione pubblicata dall'editore
Dimensione 7.15 MB
Formato Adobe PDF
7.15 MB Adobe PDF   Visualizza/Apri   Richiedi una copia
Pubblicazioni consigliate

Licenza Creative Commons
I metadati presenti in IRIS UNIMORE sono rilasciati con licenza Creative Commons CC0 1.0 Universal, mentre i file delle pubblicazioni sono rilasciati con licenza Attribuzione 4.0 Internazionale (CC BY 4.0), salvo diversa indicazione.
In caso di violazione di copyright, contattare Supporto Iris

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11380/1154590
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 53
  • ???jsp.display-item.citation.isi??? 45
social impact