Analysis of the hardness ratio effect on the tribological performance of NiCrBSi coating/debris particles using the Stribeck Curve

• Published in: Wear Vol. 486-487; p. 204081
• Main Authors: Habib, K.A., Cano, D.L., Heredia, José Antonio, Serrano-Mira, J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-12-2021; Elsevier Science Ltd
• Subjects: Ceramic powders; Chromium; Coefficient of friction; Debris; Hardness; Hardness ratio; Lubricants; Lubricants & lubrication; Lubrication; Lubrication regime; Metal powders; Morphology; NiCrBSi coating; Particle size distribution; Surface roughness; Tribology; Wear rate; Yttrium oxide; Zirconium; Surface roughness; NiCrBSi coating; Hardness ratio; Debris; Lubrication regime
• ISSN: 0043-1648; 1873-2577
• DOI: 10.1016/j.wear.2021.204081

This work aims to propose an approach to estimate the final surface roughness as a function of the hardness ratio between coating and debris (Hpin/Hdebris = Hp/Hd) under lubricated conditions employing pin-on-disc configuration. Using this approach provides a better understanding and prediction of the lubrication regime (Stribeck Curve) compared with the traditional approach that uses the initial surface roughness. Our results demonstrate that a lower hardness ratio induces a higher friction coefficient and contributes to a marked increase in wear rate in lubricated conditions. To find an effective method for simulating the debris effect, four types of NiCrBSi powders were used as a source of debris: two metallic powders with a completely spherical morphology but different Cr concentrations and two other NiCrBSi (15.25%Cr) powders mixed with different concentrations 40 and 60% of ceramic, Zr + 7% Y2O3 (ZSP), composed of spherical particles morphology. Therefore, a set of four sources of debris material specimens were simulated by different types of particles with a similar size distribution but different average hardness. Each of these particles was dispersed in an oil lubricant. Observation of the worn surfaces using a rugosimeter and scanning electron microscope suggested that, together with the shape, size and number of debris, the hardness ratio must be considered when studying the tribological behavior of machine components. The proposed methodology may help to predict the variation in lubrication regime parameters (Stribeck curve) by controlling the hardness ratio.
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•Measured the effect of hardness ratio (Hpin/Hdebris) on the friction coef, wear and lubrication regimes (Stribeck curve).•The relation between the hardness ratio and final surface roughness is not linear but piecewise.•How relationship between hardness ratio, surface roughness and friction coef can improve design and maintenance operations.•Introduction of hardness ratio in tribology studies allows better computation of the lubrication regime parameters.