Wear and corrosion of niobium carbide coated AISI 52100 bearing steel

• Published in: Surface & coatings technology 2015-10, Vol.279, p.112-117
• Main Authors: Fernandes, F.A.P., Gallego, J., Picon, C.A., Tremiliosi Filho, G., Casteletti, L.C.
• Format: Article
• Language: English
• Subjects: Bearing steels; Carbides; Chromium steels; Coating; Coatings; Corrosion; Hardness; NbC; Niobium carbide; Protective coatings; Thermo-reactive deposition; Wear; Wear resistance
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2015.08.036

Bearing steels must have high hardness, good wear resistance and dimensional stability. In the present work, the AISI 52100 bearing steel was selected as the substrate for a niobium carbide coating produced by a salt-bath thermo-reactive deposition process. The present work addresses the effect of niobium carbide coating on the wear and corrosion resistance of the abovementioned steel. A homogeneous layer composed solely by the cubic niobium carbide (NbC) was produced. The carbide coating yielded average hardness and elastic modulus of 26GPa and 361GPa, respectively. No significant decarburization was detected beneath the case by means of hardness fluctuations. Dry wear tests resulted in worn volumes 10 times smaller for the NbC coated steel, comparatively to the untreated substrate, at three different applied loads. Corrosion tests in NaCl solution indicated an improved behavior for the carbide coated bearing steel at applied potentials inferior than 250mV. At higher potentials, the electrolyte appears to penetrate trough the layer yielding wide corrosion caps. •Microstructural, wear and corrosion characterization of NbC layers produced by the TRD technique is provided.•Worn volume is reduced by a factor of ten after the TRD treatment.•Corrosion tests in NaCl solution indicate an improved behavior for NbC at applied potentials lower than 250mV.•Additional discussion on the corrosion mechanism of NbC layers in provided.