Special Issue "Cermets and Hardmetals"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 May 2018)

Special Issue Editor

Guest Editor
Prof. Dr. Kevin Plucknett

Department of Mechanical Engineering, Dalhousie University, Halifax, NS B3H 4R2, Canada
Website | E-Mail
Interests: coatings; powder metallurgy; tribology; advanced structural and functional ceramics; composites (including fibre-reinforced); inorganic foams and porous materials; materials processing; mechanical behavior; electron microscopy; oxidation and corrosion; biopolymers

Special Issue Information

Dear Colleagues,

Ceramic–metal composites, or cermets, are widely used in demanding wear and corrosion applications, as both bulk materials and coatings. Common implementation areas include tooling for grinding, cutting and machining, mechanical seals, friction surfaces, aerospace coatings, etc. The most ubiquitous example of cermets are based on WC-Co, which are typically referred to as ‘hardmetals’, and have been actively developed for many decades. More recently, lightweight systems based on alternate carbides, borides and nitrides have come to prominence. The mechanical, wear and corrosion properties of these composite systems are highly dependent on their composition and microstructure, and there is an increasing drive towards nano-structured cermets, particularly for their improved wear response. In many scenarios, tribo-corrosion environments are also encountered, such that the physical and chemical demands on the materials are extreme. Consequently, there is a continuing research demand for new cermet and hardmetal systems. The primary aim of this Special Issue is, therefore, to provide a platform for researchers to overview the current state-of-the-art in the development, characterization and applications of high performance ceramic-metal composites. 

Prof. Dr. Kevin Plucknett
Guest Editor

Manuscript Submission Information

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Keywords

  • Processing studies (including emerging technologies such as spark plasma sintering and additive manufacturing)
  • Raw materials evaluation and replacement (resource scarcity, alternative constituents)
  • Cermet and hardmetal coating development (including cladding technologies)
  • Functionally graded structures and hierarchical materials
  • Microstructural characterization of advanced cermets and hardmetals
  • Mechanical behavior (including ductile phase toughening)
  • Wear, corrosion and tribo-corrosion of cermets and hardmetals
  • Modelling of physical behavior
  • Commercial applications (current and emerging)

Published Papers (7 papers)

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Research

Open AccessArticle Microstructure, Wear Behavior and Corrosion Resistance of WC-FeCrAl and WC-WB-Co Coatings
Metals 2018, 8(6), 399; https://doi.org/10.3390/met8060399
Received: 24 April 2018 / Revised: 22 May 2018 / Accepted: 28 May 2018 / Published: 30 May 2018
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Abstract
The paper is focused on investigating the quality of two grades of thermally sprayed coatings deposited by high-velocity oxygen fuel (HVOF) technology. One grade contains WC hard particles in an environmentally progressive Ni- and Co-free FeCrAl matrix, while the second coating contains WC
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The paper is focused on investigating the quality of two grades of thermally sprayed coatings deposited by high-velocity oxygen fuel (HVOF) technology. One grade contains WC hard particles in an environmentally progressive Ni- and Co-free FeCrAl matrix, while the second coating contains WC and WB hard particles in a cobalt matrix. The aim of the experimental work was to determine the effect of thermal cyclic loading on the coatings’ resistance to adhesive, abrasive and erosive wear. Abrasive wear was evaluated using abrasive cloth of two grit sizes, and erosive wear was evaluated by a dry-pot wear test in a pin mill at two sample angles. Adhesion wear resistance of the coatings was determined by a sliding wear test under dry friction conditions and in a 1 mol water solution of NaCl. Corrosion resistance of the coatings was evaluated using potentiodynamic polarization tests. Metallographic cross-sections were used for measurement of the microhardness and thickness and for line energy-dispersive X-ray (EDX) analysis. The tests proved the excellent resistance of both coatings against adhesive, abrasive, and erosive wear, as well as the ability of the WC-WB-Co coating to withstand alternating temperatures of up to 600 °C. The “green carbide” coating (WC-FeCrAl) can be recommended as an environmentally friendly replacement for Ni- and Co-containing coatings, but its operating temperature is strictly limited to 500 °C in air. Full article
(This article belongs to the Special Issue Cermets and Hardmetals)
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Open AccessArticle The Aqueous Electrochemical Response of TiC–Stainless Steel Cermets
Metals 2018, 8(6), 398; https://doi.org/10.3390/met8060398
Received: 5 March 2018 / Revised: 27 April 2018 / Accepted: 23 May 2018 / Published: 30 May 2018
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Abstract
A family of TiC–stainless steel ceramic–metal composites, or cermets, has been developed in the present study, using steel grades of 304 L, 316 L, or 410 L as the binder phase. Melt infiltration was used to prepare the cermets, with the steel binder
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A family of TiC–stainless steel ceramic–metal composites, or cermets, has been developed in the present study, using steel grades of 304 L, 316 L, or 410 L as the binder phase. Melt infiltration was used to prepare the cermets, with the steel binder contents varying between 10–30 vol. %. The corrosion behaviour was evaluated using a range of electrochemical techniques in an aqueous solution containing 3.5 wt. % NaCl. The test methods included potentiodynamic, cyclic, and potentiostatic polarisation. The corroded samples were subsequently characterised using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), while the post-corrosion solutions were analysed using inductively coupled plasma optical emission spectroscopy (ICP-OES) to determine the residual ionic and particulate material removed from the cermets during electrochemical testing. It was demonstrated that the corrosion resistance was enhanced through decreasing the steel binder content, which arises due to the preferential dissolution of the binder phase, while the TiC ceramic remains largely unaffected. Increasing corrosion resistance was observed in the sequence TiC-304 L > TiC-316 L > TiC-410 L. Full article
(This article belongs to the Special Issue Cermets and Hardmetals)
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Open AccessFeature PaperArticle Effect of Carbon Content on the Microstructure and Mechanical Properties of NbC-Ni Based Cermets
Metals 2018, 8(3), 178; https://doi.org/10.3390/met8030178
Received: 11 January 2018 / Revised: 21 February 2018 / Accepted: 6 March 2018 / Published: 12 March 2018
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Abstract
The aim of this work was to correlate the overall carbon content in NbC-Ni, NbC-Ni-VC and NbC-Ni-Mo starting powders with the resulting microstructure, hardness, and fracture toughness of Ni-bonded NbC cermets. A series of NbC-Ni, NbC-Ni-VC and NbC-Ni-Mo cermets with different carbon content
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The aim of this work was to correlate the overall carbon content in NbC-Ni, NbC-Ni-VC and NbC-Ni-Mo starting powders with the resulting microstructure, hardness, and fracture toughness of Ni-bonded NbC cermets. A series of NbC-Ni, NbC-Ni-VC and NbC-Ni-Mo cermets with different carbon content were prepared by conventional liquid phase sintering for 1 h at 1420 °C in vacuum. Microstructural analysis of the fully densified cermets was performed by electron probe microanalysis (EPMA) to assess the effect of carbon and VC or Mo additions on the NbC grain growth and morphology. A decreased carbon content in the starting powder mixtures resulted in increased dissolution of Nb, V, and Mo in the Ni binder and a decreased C/Nb ratio in the NbC based carbide phase. The Vickers hardness (HV30) and Palmqvist indentation toughness were found to decrease significantly with an increasing carbon content in the Mo-free cermets, whereas an antagonistic correlation between hardness and toughness was obtained as a function of the Mo-content in Mo-modified NbC cermets. To obtain optimized mechanical properties, methods to control the total carbon content of NbC-Ni mixtures were proposed and the prepared cermets were investigated in detail. Full article
(This article belongs to the Special Issue Cermets and Hardmetals)
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Open AccessFeature PaperArticle Mechanical and Tribological Properties of Al2O3-TiC Composite Fabricated by Spark Plasma Sintering Process with Metallic (Ni, Nb) Binders
Metals 2018, 8(1), 50; https://doi.org/10.3390/met8010050
Received: 21 December 2017 / Revised: 6 January 2018 / Accepted: 10 January 2018 / Published: 12 January 2018
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Abstract
Al2O3-10TiC composites were fabricated through the powder metallurgical process (mechanical milling combined with spark plasma sintering) with the addition of Ni/Nb as metallic binders. The effect of binder addition (Ni/Nb) on the processing, microstructure, and mechanical and tribological properties
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Al2O3-10TiC composites were fabricated through the powder metallurgical process (mechanical milling combined with spark plasma sintering) with the addition of Ni/Nb as metallic binders. The effect of binder addition (Ni/Nb) on the processing, microstructure, and mechanical and tribological properties of the bulk-sintered composite samples was investigated. The microstructure of the composite reveals a homogeneous distribution of the TiC particles in the Al2O3 matrix. However, the presence of Ni/Nb was not traceable, owing to the small amounts of Ni/Nb addition. Hardness and density of the composite samples increase with the increasing addition of Nb (up to 2 wt. % Nb). Any further increase in the Nb content (3 wt. %) decreases both the hardness and the wear resistance. However, in case of Ni as binder, both the hardness and wear resistance increases with the increase in the Ni content from 1 wt. % to 3 wt. %. However, the composite samples with Nb as binder show improved hardness and wear resistance compared to the composites with Ni as binder. Full article
(This article belongs to the Special Issue Cermets and Hardmetals)
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Open AccessArticle Surface Characterization and Corrosion Resistance of 36Cr-Ni-Mo4 Steel Coated by WC-Co Cermet Electrode Using Micro-Electro Welding
Metals 2017, 7(8), 308; https://doi.org/10.3390/met7080308
Received: 5 July 2017 / Revised: 24 July 2017 / Accepted: 25 July 2017 / Published: 12 August 2017
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Abstract
In this paper the influence of spark energy on corrosion resistance, hardness, surface roughness and morphology of WC-Co coated 36Cr-Ni-Mo4 steel by Micro-Electro Welding (MEW) was investigated. Frequencies of 5, 8 and 11 kHz, currents of 15, 25 and 35 A and duty
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In this paper the influence of spark energy on corrosion resistance, hardness, surface roughness and morphology of WC-Co coated 36Cr-Ni-Mo4 steel by Micro-Electro Welding (MEW) was investigated. Frequencies of 5, 8 and 11 kHz, currents of 15, 25 and 35 A and duty cycles of 10, 30 and 50 % were applied for coating of the samples using a WC-Co cermet electrode. The results indicate that increasing the current, Duty cycle and frequency of the process increases spark energy. As spark energy increases, efficiency of coating increases to 80% and then decreases. X-ray diffraction (XRD) analysis was used to identify the phases. The results indicated that other than the peaks obtained for the metallic Iron with BCC (Body Centered Cubic) structure, Tungsten Carbide, Cr7C3 and Titanium Carbide phases were also seen on the surface. Vickers micro hardness method was used for hardness measurement of the samples. Surface hardness increases to 817.33 HV0.05 with spark energy increasing up to 1.03 mJ, and then reducing. Optical Microscopy (OM) and scanning electron microscopy (SEM) to study Microstructural and atomic force microscopy (AFM) to study the topography, morphology and roughness were used. Polarization technique in 3.5 wt % NaCl solution was used to evaluate the corrosion properties. The results of the energy dispersive X-ray spectroscopy (EDS) analysis indicate that with increasing spark energy, the amount of Tungsten in surface increases to 41.95 wt % and then decreases. As spark energy increases up to 2.17 mJ, thickness of coating increases to 8.31 μm and then decreases. As spark energy increases, surface roughness is also increased. Corrosion test results indicated that the lowest corrosion rate (2.6 × 10−8 mpy) is related to the sample with the highest level of efficiency. Full article
(This article belongs to the Special Issue Cermets and Hardmetals)
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Open AccessArticle Vickers Indentation Fracture Toughness of Near-Nano and Nanostructured WC-Co Cemented Carbides
Metals 2017, 7(4), 143; https://doi.org/10.3390/met7040143
Received: 13 January 2017 / Revised: 1 April 2017 / Accepted: 12 April 2017 / Published: 19 April 2017
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Abstract
In this paper, the fracture toughness KIc of near-nano and nanostructured WC-Co cemented carbides by Vickers indentation fracture toughness (VIF) was investigated. The aim was to research the type of cracking occurring in near-nano and nano-grained WC-Co cemented carbides with respect to
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In this paper, the fracture toughness KIc of near-nano and nanostructured WC-Co cemented carbides by Vickers indentation fracture toughness (VIF) was investigated. The aim was to research the type of cracking occurring in near-nano and nano-grained WC-Co cemented carbides with respect to the Co content and, consequently, to evaluate the appropriateness of different models for the fracture toughness calculation. The mixtures with different binder content—4, 6, and 9 wt. % Co—were consolidated by sintering in a hydrogen atmosphere. Vickers indentation using a test force of 294 N was used for the determination of fracture toughness. The type of crack that occurred as a consequence of the applied load on the corners of the Vickers indentations was analysed with optical microscopy before and after repolishing the samples. Different crack models, Palmqvist and radial-median, were applied for the calculation of KIc. Instrumented indentation testing was used to determine the modulus of elasticity of the consolidated samples. From the research it was found that near-nano and nanostructured cemented carbides with 9 and 6 wt. % Co do not exhibit median cracking and the indenter cracks remain radial in nature, while near-nano and nanostructured cemented carbides with 4 wt. % Co exhibit both radial and median cracking. Accordingly, it was concluded that the critical amount of the binder phase in near-nano and nanostructured WC-Co at which the crack changes its geometry from Palmqvist to radial-median is around 4 wt. % Co. Comparing different models it was found that KIc values are not consistent and differ for each method used. Models from Exner crack resistance for the Palmqvist crack showed good agreement. Radial-median crack models showed significant KIc deviations for the same testing conditions for all samples. Full article
(This article belongs to the Special Issue Cermets and Hardmetals)
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Open AccessArticle Electrochemical Corrosion Behavior of Near-Nano and Nanostructured WC-Co Cemented Carbides
Metals 2017, 7(3), 69; https://doi.org/10.3390/met7030069
Received: 1 December 2016 / Revised: 29 January 2017 / Accepted: 17 February 2017 / Published: 23 February 2017
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Abstract
In this paper, the electrochemical corrosion resistance of near-nano and nanostructured WC-Co cemented carbides was investigated. WC powders with an average grain size dBET in the range from 95 nm to 150 nm and with an addition of vanadium carbide (VC) and
[...] Read more.
In this paper, the electrochemical corrosion resistance of near-nano and nanostructured WC-Co cemented carbides was investigated. WC powders with an average grain size dBET in the range from 95 nm to 150 nm and with an addition of vanadium carbide (VC) and chromium carbide Cr3C2 as grain growth inhibitors were used as starting powders. The mixtures with 6 wt. % and 9 wt. % Co were consolidated by two different processes; sintering in hydrogen atmosphere and the sinter-HIP process. WC-Co samples were researched by direct current and alternating current techniques in the solution of 3.5% NaCl at room temperature. Corrosion parameters such as corrosion potential (Ecorr), corrosion current density (jcorr) and polarization resistance (Rp) were determined by electrochemical techniques. From the conducted research, it was found that the consolidation processes and microstructural characteristics—grain growth inhibitors, grain size of the starting WC powders and η-phase—influenced the electrochemical corrosion resistance. η-phase enhanced the formation of a passive layer on the samples’ surfaces, thereby reducing the tendency of the sample dissolution and increasing the stability of oxides forming therewith a passive layer on the sample surface. Full article
(This article belongs to the Special Issue Cermets and Hardmetals)
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