Cr-rich layer at the WC/Co interface in Cr-doped WC–Co cermets: segregation or metastable carbide?

A theoretical model for understanding the formation of interfacial thin films is presented, which combines density functional theory calculations for interface energies with thermodynamic modeling techniques for multicomponent bulk systems. The theory is applied to thin film formation in VC-doped WC-Co cemented carbides. It is predicted that ultrathin VC films may exist in WC/Co interfaces at the high temperature sintering conditions where most of the WC grain growth occurs, which provides an explanation of the grain growth inhibiting effect of VC additions in the WC-Co system.

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“…This orientation relationship between WC and MC has been experimentally established for both V-and Cr-doped WC-Co [18,23].…”

Section: Specific Model and Methodsmentioning

confidence: 64%

Theory of ultrathin films at metal–ceramic interfaces

Johansson

Wahnström

2010

Philosophical Magazine Letters

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“…The light gray middle layer has 700 nm of thickness, it has a high chromium content, and cobalt and tungsten were also identified, which suggests diffusion of cobalt and tungsten through the porous oxidized coating. The chromium is located mainly in the Co binder phase and can be found as Cr-rich precipitates, M 7 C 3 , in the binder during the cooling for large Cr content [27].…”

Section: Microstructural Characterisation After Annealing In Argonmentioning

confidence: 99%

Effect of Silicon Addition on Microstructure and Mechanical Properties of Chromium and Titanium Based Coatings

Ardila-Téllez¹,

Sanchez

Téllez

2014

Fac. Ing.

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<p>The changes in the microstructure, mechanical properties and residual stresses of AlTiN, AlTiSiN, AlCrN and AlCrSiN coatings, has been studied before and after annealing at 900 ºC and 1100 ºC, using scanning and transmission electron microscopy, along with nano-indentation and X-ray diffraction techniques. The As-deposited coatings show a columnar structure, with a crystallite size between 18 nm and 28 nm. Despite the silicon addition, no effect on the crystallite size refinement was observed.<br />However, the addition of silicon increases hardness, elastic modulus and compressive residual stresses. After annealing at 900 ºC, the crystallite size growth and the residual stress relaxes; therefore, the coating hardness decreases. At 1100 ºC, the oxide layers formed in AlTiN and AlTiSiN, which act as protective layers enhancing oxidation resistance; meanwhile, a complete oxidation of AlCrN and AlCrSiN coatings take place. The Titanium based coatings present some superior mechanical properties and oxidation resistance than the chromium based coatings at 900 ºC and 1100 ºC.</p>

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“…It is well known from high-resolution transmission electron microscope (HRTEM) imaging that the atomic structure of the WC(0001) surface in contact with Co deviates from that of bulk WC, 16,17,[34][35][36][37][38][39][40][60][61][62] especially when the WC-Co system is doped with Ti, V, or Cr. In Refs.…”

Section: B Structural Modelsmentioning

confidence: 99%

First-principles study of an interfacial phase diagram in the V-doped WC-Co system

Johansson

Wahnström

2012

Phys. Rev. B

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We present a method of determining an interfacial phase diagram using density functional theory calculations for interface energetics. Cluster expansions based on these calculations are used in Monte Carlo simulations to obtain configurational free energies. The method is applied to study the segregation of V to the WC(0001)/Co interface and to construct the corresponding interface diagram, a "complexion" phase diagram. By CALPHADtype analysis for the adjoining bulk phases, a connection with real materials is made. We find that, in equilibrium, the interface contains a thin V-rich film for a wide range of temperatures and chemical potentials of V corresponding to V additions below the (V,W)C x solubility limit. The results are compared with available experimental data, and implications of the strong segregation of V for the sintering process of V-doped WC-Co are discussed.

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Cr-rich layer at the WC/Co interface in Cr-doped WC–Co cermets: segregation or metastable carbide?

Cited by 93 publications

References 29 publications

Theory of ultrathin films at metal–ceramic interfaces

Theory of ultrathin films at metal–ceramic interfaces

Effect of Silicon Addition on Microstructure and Mechanical Properties of Chromium and Titanium Based Coatings

First-principles study of an interfacial phase diagram in the V-doped WC-Co system

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