Thermal spray coatings based on WC-CoCr are widely employed to protect industrial components against wear and corrosion. Although they provide good technical performances, it is necessary to replace Co-based hardmetal compositions to protect human health as well as for economic reasons. Alternative hardmetal formulations with little or no Cobalt were deposited by High Velocity Oxygen-Fuel (HVOF) spraying using agglomerated and sintered feedstock powders. They consist of WC as hard phase, but metallic matrices include iron- and nickel- based alloys (WC-NiMoCrFeCo, WC-FeNiCrMoCu, WC-FeCrAl). The characterization is focused on micro- structure, mechanical and tribological properties (sliding and abrasive wear behaviour) and corrosion resistance in 3.5% NaCl. Very low porosity, limited carbides' dissolution in the matrix, deposition efficiency ≥50%, and hardness values (≈1200 HV) comparable to conventional WC-CoCr mean that the studied coatings are viable for industrial applications. Both WC-NiMoCrFeCo and WC-FeNiCrMoCu coatings show intrinsically high sliding wear resistance (specific wear rates between 10−8 and 10−7 mm3/(N∙m) in a ball-on-disc test against Al2O3 counterpart), but they are less resistant to high-stress abrasion by coarse particles (wear rates ≈10−3 mm3/ (N∙m)). Their performances are anyway comparable to those of reference WC-CoCr samples. Additionally, WC- NiMoCrFeCo coatings show even better corrosion resistance in a 3.5% NaCl aqueous solution (ICorr ~ 10−6 A/ cm2). WC-FeCrAl coatings exhibit slightly poorer performances than the other samples: the formation of Al-based oxide inclusions during spraying cause higher wear losses, whilst the FeCrAl matrix has limited corrosion re- sistance.

Alternative metallic matrices for WC-based HVOF coatings / Testa, Veronica; Morelli, Stefania; Bolelli, Giovanni; Benedetti, Beatrice; Puddu, Pietro; Sassatelli, Paolo; Lusvarghi, Luca. - In: SURFACE & COATINGS TECHNOLOGY. - ISSN 0257-8972. - 402:(2020), pp. 1-27. [10.1016/j.surfcoat.2020.126308]

Alternative metallic matrices for WC-based HVOF coatings

Veronica Testa;Stefania Morelli;Giovanni Bolelli;Beatrice Benedetti;Pietro Puddu;Paolo Sassatelli;Luca Lusvarghi
2020-01-01

Abstract

Thermal spray coatings based on WC-CoCr are widely employed to protect industrial components against wear and corrosion. Although they provide good technical performances, it is necessary to replace Co-based hardmetal compositions to protect human health as well as for economic reasons. Alternative hardmetal formulations with little or no Cobalt were deposited by High Velocity Oxygen-Fuel (HVOF) spraying using agglomerated and sintered feedstock powders. They consist of WC as hard phase, but metallic matrices include iron- and nickel- based alloys (WC-NiMoCrFeCo, WC-FeNiCrMoCu, WC-FeCrAl). The characterization is focused on micro- structure, mechanical and tribological properties (sliding and abrasive wear behaviour) and corrosion resistance in 3.5% NaCl. Very low porosity, limited carbides' dissolution in the matrix, deposition efficiency ≥50%, and hardness values (≈1200 HV) comparable to conventional WC-CoCr mean that the studied coatings are viable for industrial applications. Both WC-NiMoCrFeCo and WC-FeNiCrMoCu coatings show intrinsically high sliding wear resistance (specific wear rates between 10−8 and 10−7 mm3/(N∙m) in a ball-on-disc test against Al2O3 counterpart), but they are less resistant to high-stress abrasion by coarse particles (wear rates ≈10−3 mm3/ (N∙m)). Their performances are anyway comparable to those of reference WC-CoCr samples. Additionally, WC- NiMoCrFeCo coatings show even better corrosion resistance in a 3.5% NaCl aqueous solution (ICorr ~ 10−6 A/ cm2). WC-FeCrAl coatings exhibit slightly poorer performances than the other samples: the formation of Al-based oxide inclusions during spraying cause higher wear losses, whilst the FeCrAl matrix has limited corrosion re- sistance.
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Alternative metallic matrices for WC-based HVOF coatings / Testa, Veronica; Morelli, Stefania; Bolelli, Giovanni; Benedetti, Beatrice; Puddu, Pietro; Sassatelli, Paolo; Lusvarghi, Luca. - In: SURFACE & COATINGS TECHNOLOGY. - ISSN 0257-8972. - 402:(2020), pp. 1-27. [10.1016/j.surfcoat.2020.126308]
Testa, Veronica; Morelli, Stefania; Bolelli, Giovanni; Benedetti, Beatrice; Puddu, Pietro; Sassatelli, Paolo; Lusvarghi, Luca
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11380/1208333
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