Tribological Behavior of Ni-Based WC-Co Coatings Deposited via Spray and Fuse Technique Varying the Oxygen Flow

H Jiménez,J E Alfonso,J J Olaya,João P Davim

doi:10.1155/2021/8898349

H Jiménez, J E Alfonso + Show 2 more

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https://doi.org/10.1155/2021/8898349

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Abstract

The tribological behavior of Ni-based WC-Co coatings is analyzed. The coatings were deposited on gray cast iron substrates in a spray and fuse process using SuperJet Eutalloy deposition equipment, varying the oxygen flow conditions in the flame. The crystallographic structure of the coatings was characterized via the X-ray diffraction (XRD) technique. The microhardness was measured on the surface and in cross sections of the coatings by means of a Knoop microhardness tester. The topography and the morphological characteristics of the coatings and the tribo-surfaces were examined using scanning electron microscopy (SEM) and confocal microscopy, while the chemical composition was measured by means of energy-dispersive X-ray spectroscopy (EDS). The tribological behavior of the coatings was examined via a cohesion-adhesion scratch test, using cross sections of the coatings. Furthermore, two wear tests were carried out, using the pin-on-disk method under ASTM G99 standard and an ASTM standard G65 sand/rubber wheel abrasion wear test. The wear of the coatings showed a close relationship to the porosity in the metal matrix; since then, in the abrasive wear test, a high porosity is related with lower hardness in the coatings; likewise, a low hardness is related with a high wear.

Highlights

WC-Co coatings are frequently used in wear-resistance applications due to their tribological properties [1, 2].ese coatings have been deposited mainly using thermal spray techniques, such as high-velocity oil fuel (HVOF), arc spray, plasma spraying, and detonation spray coating [3, 4]. e spray and fuse thermal spray process has important advantages compared to other thermal spray techniques due to the ease of production of the coatings, the wide variety of geometries and surfaces that can be coated, the relatively low cost of coating production, and the ease of handling of the equipment
In the deposition process of the coatings, the gray cast iron substrate is preheated to temperatures between 500 and 600°C, the filler material is sprayed onto the substrate, and this material is melted onto the substrate, forming the coating
In a previous investigation [16], we found that the X-ray diffraction (XRD) pattern that corresponds to MetaCeram powder exhibits Ni3B and Ni peaks with Ni reflections in crystallographic planes (111), (200), (220), (311), and (222), according to the X’Pert HighScore card, with reference code: 03-065-2865

Summary

Introduction

WC-Co coatings are frequently used in wear-resistance applications due to their tribological properties [1, 2].ese coatings have been deposited mainly using thermal spray techniques, such as high-velocity oil fuel (HVOF), arc spray, plasma spraying, and detonation spray coating [3, 4]. e spray and fuse thermal spray process has important advantages compared to other thermal spray techniques due to the ease of production of the coatings, the wide variety of geometries and surfaces that can be coated, the relatively low cost of coating production, and the ease of handling of the equipment. Some applications of the cermet coatings have been reported by some authors like Szymanski et al, who found that coatings produced by thermal spray techniques have shown high resistance to corrosion and erosion in industry applications. Failure analysis of cermet coatings deposited by HBOF technique showed that Yttria reinforced WC-10Co4Cr coating has superior triboresistance and mechanical properties, while WC-10Co4Cr coating showed good wear resistance in fly ash slurry which possesses a weak acidic nature. Erefore, the oxygen flow is a very important parameter in mechanical and tribological properties of the coatings grew via thermal spray technique; the reports found in the literature in this regard are poor [11,12,13,14,15] We describe the tribological behavior of Ni-based WC-Co coatings deposited via the spray and fuse technique and evaluate the tribological behavior as a function of the oxygen flux. e reports regarding the variation of the oxygen flow in thermal spray systems are extensive, and authors such as Bandgopadhyag et al and Nylen used computer software to model the effect of the oxygen flow on the distribution of speeds and temperatures in an oxyacetylene flame. e heat power Pf dissipated by the flame depends on the fuel/oxidant ratio and the fuel gas feed rate, mu; as the limiting factor in combustion is mO2, it can be said that Pf is proportional to the oxygen flow. erefore, the oxygen flow is a very important parameter in mechanical and tribological properties of the coatings grew via thermal spray technique; the reports found in the literature in this regard are poor [11,12,13,14,15]

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