Influence of binder metal and surface treatment on the corrosion resistance of (W,Ti)C-based hardmetals

Abstract

The effect of a nitridation surface treatment on the microstructure and corrosion resistance of Co and Ni-binder (W,Ti)C-based hardmetals with additions of (Ta,Nb)C was investigated. Nitridation treatment produces a surface layer with a higher hard phase (Ti,Ta,Nb,W)(C,N) content. The near-surface layer thickness and microstructure are affected by the choice of binder (Co respectively Ni). The corrosion resistance of the hardmetals was characterized using linear sweep voltammetry. The microstructure of the hardmetals was determined before and after corrosive attack by optical microscopy and SEM. The results of the corrosion tests and microstructure analyses are interpreted in terms of the correlation between the hardmetal morphology and porosity and ion transport through the interface binder-electrolyte. The nitridation treatment of the hardmetals strongly increases the resistance to aggressive corrosion media for hardmetals both with Co and Ni-binder phase and thus may positively influence the hardmetal lifetime in cutting applications in chemically aggressive environments.

Cyclic contact fatigue of cemented carbides under dry and wet conditions: Correlation between microstructure, damage and electrochemical behavior

“…A second zone, known as a delamination area (labelled as ( 2)) can be seen, characterized by a loss of material in an area corresponding to a ring where the carbides are detached. As it is evident, the metallic binder suffers an anodic oxidation reaction and it is dissolved in the cutting fluid as previously reported for acid media [14,15,17]. This trend means that the effective leaching of the metallic phase takes place and thus, the onset of microcrack-like voids, in concordance with the work reported by Tarragó et al [8].…”

“…acid, caustic and neutral solutions as reported in Refs. [14][15][16][17][18][19]. However, these components usually work under cutting fluid and scarce information in this medium is available in the literature.…”

Assessment of corrosion-induced changes on the mechanical integrity of cemented carbides at small length scales

“…M A N U S C R I P T hardmetals has been extensively investigated in recent decades using different testing methodologies and addressing influence of multiple factors, such as surface state, corrosive medium, microstructural assemblage and binder chemical nature [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. In these studies, it has been shown that: (1) corrosive media preferentially attack the binder phase when exposed to acidic and neutral environments; (2) in alkaline solution, the Co binder exhibits a stable passivation, while the WC phase dissolves easily; (3) damage by corrosion induced by acidic media is usually much more pronounced than that of neutral and basic ones; and (4) a greater amount of dissolution of the binder phase in acid solution eventually results in the formation of the oxide layer of W and a re gion depleted in Co, compared to the exposure in neutral and basic solutions.…”

Corrosion damage in WC–Co cemented carbides: residual strength assessment and 3D FIB-FESEM tomography characterisation

“…Refs. [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. From these studies, several microstructural effects on corrosion response for these materials may be highlighted.…”