Mechanical and tribocorrosion properties of HVOF sprayed WC–Co coatings

Abstract

HVOF technology has been proposed in recent years for the production of engineered cermet coatings suitable for the replacement of hard chromium surface treatments of mechanical components, for aeronautical and automotive applications. The aim of this study has been to compare the mechanical and tribocorrosion properties of WC-Co cermet coatings fabricated with different processing parameters, to optimise the spraying process by evaluating the dependence of the macroscopic coating properties on the spraying procedure.Barrel length, oxygen:fuel ratio and torc-/ specimen spraying distance were selected as the main variables since their influence on coating microstructure and macroscopic properties in the absence of corrosion is already well known. WC-Co samples were subjected to 'block on ring' wear testing, carried out in an electrochemical cell, to assess wear properties in combination with a range of corrosive conditions. The results were compared to those obtained by ordinary wear testing and electrochemical characterisation. Mechanical properties of the coatings, such as microhardness, fracture toughness and coating-substrate adhesion, were also measured. Tribocorrosion testing proved better able to distinguish coating properties than conventional wear tests, due to the more severe damage induced by the corrosive attack.CEST/2144

Erosion Wear Investigation of HVOF Sprayed WC-10Co4Cr Coating on Slurry Pipeline Materials

“…The average roughness of uncoated mild steel, SS202, and SS304 is observed as 2.45, 1.35, and 1.38 µm, whereas the values were 4.89, 4.63, and 4.58 µm after deposit coating. The investigators suggested that cutting, fracture, and abrasion are the major modes of erosion wear mechanisms that are relevant to slurry pipelines [2,3,13,14]. The eroded images of WC-10 Co 4 Cr-coated mild steel, SS202, and SS304 with EDS (energy dispersive spectroscopy) are shown in Figures 6-8.…”

“…These coatings can provide a hard layer of carbides, oxides, and nitrides of Cr, W, Al, and Ti [10,11]. The high-velocity oxy-fuel (HVOF) technique can be applied to deposit coatings with high cohesive strength and superior mechanical properties [10][11][12][13][14]. In the present work, erosion wear behavior of three piping materials, namely, mild steel, SS202, and SS304, have been analyzed with and without a HVOF-sprayed WC- 10 Co 4 Cr coating.…”

Tribo-corrosion of coatings: a review

“…low pH) from the bulk conditions and induce crevice corrosion, which in turn contributes to increased C e levels. The influence of the spraying parameters (spraying distance, barrel length and kerosene flow rate) on the tribo-corrosion performance of HVOF sprayed WC-17Co coatings has been studied by Valentinelli et al [51]. They also found that binder dissolution controlled wear-corrosion levels and therefore coating compositions should be designed with reference to the relevant Pourbaix diagrams (potential versus pH regime maps based on thermodynamic considerations only) to select compositions that are passive in the service environment and in addition have strong repassivation tendencies.…”

Wear of Flame-Sprayed Ni-Cr-B-Si Powder Coating on Journal for Seal Contact

“…Bartuli et al [9] in order to force the flow equation simulation WC-Co Nano HVOF spray coating process in the best parameters, explore the combustion flame and particle flow of hot gas chemical and dynamical properties of WC-Co coated nanostructures affected layer by abrasion tests found nanostructure coating having a low coefficient of friction, and having high hardness and high fracture toughness.…”