Technical Program

Status: 3 June, 2022
Thursday, 2 June, 2022
08:30 - 10:10
Refractory Metals - High entropy alloys and RM intermetallics
Location: Walter Schwarzkopf Hall
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08:30 RM 21
Refractory high entropy alloys (RHEAs) with high melting temperature & low thermal neutron cross-section
Knowles A.1, Parkes N.1, Ferreirós P.1
1University of Birmingham, United Kingdom
Refractory Metal High-entropy alloys (RM-HEAs) with high melting points and low thermal neutron cross-section are sought for generation-IV fission and fusion reactors. A high throughput computational screening tool Alloy Search and Predict (ASAP) as used to identify best candidate HEAs from over a million four-element equimolar combinations, the selected NbTiVZr HEAs were further studied by density functional theory (DFT), and CALPHAD to predict phase formation. Experimentally the NbTiVZrx HEAs were found to constitute a bcc single-phase field at high temperature. However, the beta matrix decomposed following aging at 700 °C, into a combination of nano-scale phases of: beta, alpha-hcp and C15 Laves phases, characterised by electron microscopy.
08:50 RM 22
Development of materials design framework for refractory complex concentrated alloys advancing space propulsion components
Yan F.1, Walbrühl M.1, Yan J.1, Berglund I.1
1QuesTek Europe AB, Sweden
A limiting factor for space propulsion efficiency is materials availability and properties, due to the extreme environmental conditions (large temperature differentials, thermal shock, reactive propellants, etc.) that the space propulsion components are in contact with. Recent advancements on complex-concentrated alloys (CCAs), in particular refractory CCAs, have been a bold step forward with the potential to withstand high temperatures with high thermal stability. This work aims to showcase a multiscale materials design framework built to advance the state-of-the-art refractory CCAs towards the practical needs (current and future) of the space propulsion industry. The framework is intended to allow for accelerated materials designs that achieve better trade-offs between conflicting properties such as high-temperature strength, low-temperature ductility and oxidation resistance, while reducing needs for costly and time-consuming experimental studies. Examples from the ongoing development of novel additive manufacturable refractory CCAs for in-space bi-propellant thrusters will be provided, where thermal control, mechanical integrity, fuel compatibility and processability are key design factors, to ultimately increase thruster efficiency by increasing the highest allowable temperature in the combustion chamber.
09:10 RM 23
MoSiBTi by powder metallurgy
Gaitzsch U.1, Weißgärber T.1
1Fraunhofer IFAM Dresden, Germany
In the MoSiB system the berczik triangle has been established to describe a three phase field to form tough and strong high temperature materials. However adding titanium may lead to a different phase field favoring the formation of the Mo5Si3 phase over Mo3Si phase promising better creep resistance and oxidation resistance. Additionally Ti5Si3 participates may increase both strength and ductility of the alloy by reducing the silicon content in the molybdenum solid solution and at the grain boundaries. Synthesizing the material by powder metallurgy offers both new prospects and challenges towards phase formation. A thermodynamic equilibrium state, like for example a chemical homogeneous melt is never reached. In contrast local diffusion couples and the resulting phase transformations define the microstructure of the alloy depending on the used raw materials. In this study the effect of thermal treatment in SPS compacted samples on microstructure and mechanical properties is presented.
09:30 RM 24
High temperature properties of refractory based high entropy alloys
Neubauer E.1, Kovacova Z.1, Biermair F.2, Ressel G.2, Kitzmantel M.1
1RHP Technology GmbH, Austria
2Materials Center Leoben Forschung GmbH (MCL), Austria
High temperature tooling applications require materials which combine oxidation resistance, high temperature strength and hardness as well as resistance against creep. The Rapid Sinter Pressing technology is a method which allows to densify pre-compacted green bodies, which are inserted in a heated pressing die and densified within seconds. This process takes place at temperatures up to 1000 °C. The goal of the present work was the assessment of two High Entropy Alloys containing refractory metals. Al20Mo10Nb20Ta10Ti20Zr20 and Al20Cr20Mo20Nb20Ti20 powder mixtures have been prepared and densified by means of rapid hot pressing. Subsequent heat treatments were carried out in order to homogenize the microstructure. Microstructural analyses have been carried out in order to characterize the materials after processing. Oxidation testing was performed at temperatures of up to 1.200°C. Additionally mechanical testing was performed and microstructural analysis was done to analyse the materials at different conditions, e.g. after heat treatment and after oxidation testing.
09:50 RM 25
Refractory-metal-based high-entropy metal-sublattice ceramics
Kirnbauer A.1, Polcik P.2, Mayrhofer P.H.1
1TU Wien, Austria
2Plansee Composite Materials GmbH, Germany
Thin films, including borides, nitrides, and oxides, based on the high-entropy concept, were synthesised by PVD from refractory metal targets. The investigated coatings exhibit a single-phase structure independent of the varied deposition parameters. All coatings were investigated regarding their thermal stability by vacuum annealing and subsequent XRD, and hardness measurements. The results show that borides, nitrides, as well as oxides maintain their single-phase structure up to an annealing temperature Ta of at least 1200 °C. The hardness values are also maintained up to this temperature. Further increasing the annealing temperature leads to a slight decrease for nitride coatings. The investigated boride maintains its hardness of ~44 GPa even up to Ta = 1400 °C. The obtained results show, that all investigated coatings exhibit significantly enhanced thermal stability as well as retarded decomposition and softening processes compared to their respective binary systems.
10:10 - 10:30
Location: Walter Schwarzkopf Hall
10:30 - 12:10
Refractory Metals - Powders and sintering
Location: Walter Schwarzkopf Hall
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10:30 RM 26
Review of the hydrothermal oxidation processes of sulfide minerals with industrial application to the treatment of molybdenite concentrates
Segura J.1, Cisternas E.1
1Molibdenos y Metales S.A., Chile
This review considers hydrothermal processes linked to the treatment of molybdenite, in the context of industrial application in Molymet. The two processes described here are the foundation of the economy of the MolymetNos plant and are key enablers for production of molybdenum metal and high purity molybdenum compounds.

In the "cleaning" process, molybdenite is processed in a continuous autoclave in an atmosphere of pure oxygen. Under mild oxidation conditions sulfurized species of copper can solubilize and a solid product is obtained containing only molybdenum disulfide and gangue. Also, a solution of low sulfuric acidity, some molybdenum, copper, iron and other minor metals, which are recovered in downstream processes. The final copper content in molybdenite allows using it in roasting, complying with the specification for technical molybdenum oxide as a final product.

The “oxidation” process is similar, but with more energetic conditions. Sulfur species oxidize and solubilize, including molybdenum, which re-precipitates as trioxide. Molybdenum trioxide is dissolved in ammonia solution, which is the precursor to high purity molybdenum compounds.
10:50 RM 27
In-situ Powder X-ray Diffraction during Hydrogen Reduction of MoO3 to MoO2
Zoller M.1, Lund H.2, O'Sullivan M.3, Huppertz H.1
1University of Innsbruck, Austria
2Leibniz-Institute of Catalysis e.V., Germany
3Plansee SE, Austria
The hydrogen reduction of molybdenum trioxide to molybdenum dioxide is not yet fully understood as evident by continuous scientific interest. Especially the effect of the potassium content on the reduction process has not yet been considered. We prepared several samples of molybdenum trioxide containing varying amounts of potassium by addition of potassium molybdate (K2MoO4). In-situ powder X-ray diffraction experiments were then conducted to study the hydrogen reduction of these samples. We especially focused on the influence of the alkali content and on gaining insight into the importance of the intermediary product γ-Mo4O11. During the reduction process, MoO2 is formed from the reduction of MoO3, which then reacts with the starting material to form γ-Mo4O11. With increasing potassium content, the reduction rate is decreased and the fractional content of γ-Mo4O11 built up during the reduction process is increased. As evident from bulk sample reduction, this results in a significant increase in the grain size visualized via scanning electron microscopy. Our investigations once again underline the importance of γ-Mo4O11 on the morphology of the resulting MoO2 powder.
11:10 RM 28
In situ X-ray diffraction studies on the production processes of molybdenum and rhenium via reduction with hydrogen
Keilholz S.1, Kohlmann H.2
1Universität Leipzig, Institute of Inorganic Chemistry and MOLYMET Germany GmbH, Germany
2Universität Leipzig, Institute of Inorganic Chemistry, Germany
Molybdenum and rhenium powder are industrially produced by reducing MoO3 and NH4ReO4 respectively with hydrogen gas in a two-step reaction. Several important properties of the products like particle size and oxygen content are defined during the first step at 600 and 350 °C respectively, during which MoO3 is reduced to MoO2 and NH4ReO4 is reduced to rhenium. In the second step MoO2 is reduced to molybdenum at 1100 °C while rhenium is purified at 900 °C under hydrogen.
Both processes have been investigated via in situ X-ray diffraction with a particular focus on the first steps. Depending on the heating rate and hydrogen flow rate the Magnéli phase Mo4O11 as well as molybdenum bronzes can occur as an intermediate of the reduction of MoO3 and the formation of molybdenum can be observed during the first step at 600 °C.
11:30 RM 29
Tungsten heavy alloy microgravity sintering and the implications with respect to additive manufacturing away from Earth
German R.1, Torresani E.1, Olevsky E.1
For years tungsten heavy alloys have provided benchmark data on the role gravity has with respect to sintering densification and distortion. The experiments have involved a variety of compositions, temperatures, times, and two gravitational environments. The results from new experiments completed in 2021 will show the behavior for tungsten-nickel-copper-manganese compositions. Changes in the tungsten content adjust the liquid to solid ratio and changes to the nickel-copper ratio adjust the dihedral angle. Ground experiments and low Earth orbit experiments provide data with respect to two gravitational extremes. The results complicate current plans are for sending robots to additively manufacture habitats using binder jetting or filament extrusion. When placed on the Moon or Mars, we realize there is no basis for predicting final size, shape, or density. This paper extrapolates between Earth and microgravity to predict the sintering response at intermediate gravitational environments for various tungsten alloys and candidates with a lower density as found on the Moon and Mars.
11:50 RM 50
Manufacturing Process and Mechanical Properties of BJ3DP Tungsten Heavy Alloy Components
Nigarura S.1, Shah R.2, Trasorras J.3, Janka L.4, Karhumaa T.4
1Global Tungsten & Powders, USA
2Global Tungsten&Powders, USA
3Global Tungsten & Powders, USA
4Tikomet Oy, Finland
Binder jetting 3D printing (BJ3D) is an emerging technology that can enable the production of tungsten heavy alloy (WHA) parts of great geometric complexity. Despite its promise, the industrial use of BJ3DP is today hindered by two shortcomings: (i) Printed parts have low strength in the as-cured state, and (ii) the mechanical properties of the sintered parts are poor when sintered using standard sintering practice.
This study was carried out to address those shortcomings. We introduce a new WHA powder for BJ3DP and compare it to existing powders. Physical properties (flow, apparent density, size distribution) and the green strength after BJ3DP are reported.
Sintering and microstructural evolution differences between the new WHA powder, existing WHA powders for BJ3DP and conventional press-and-sinter WHA powders were investigated. Good densification during the early stages of sintering enabled the sintering of the new powder to full density. After sintering, mechanical properties of the printed specimens were evaluated and compared to the properties of cold isostatically pressed WHA specimens using conventional powder blends with similar chemistry.
The new powder has superior green strength in the as-printed condition and is therefore a better candidate for the manufacturing of complex parts. It also sinters much faster than currently available powders and achieves mechanical properties that match those of conventionally processed WHA.
10:30 - 12:10
Hard Materials - SIS on 3D Printing
Location: Lecture Hall
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10:30 HM 32
Binder Jetting 3D Printed Cemented Carbide: Printing and Properties of Medium and Coarse Grades
Wolfe T.1, Enneti R.1, Sha R.1, Prough K.1, Trasorras J.L.1
1Global Tungsten & Powders Corp., USA
Selective laser melting (SLM) is the most widely used additive manufacturing (AM) technology to 3D print metals. Several researchers have tried, unsuccessfully, to produce cemented carbide by SLM. Binder jetting 3D printing (BJ3DP) and bound metal deposition (BDM) are two AM technologies that have been successfully applied to the manufacture of cemented carbide components. We report the development of medium and coarse WC-Co powders for BJ3DP with Co content of 12%. The free flowable (Hall flow < 20 s/200g) spherical powders exhibit very good printability and can be sintered to full density under standard sinter-HIP conditions (temperature 1425-1485oC, pressure 18.3 bar).
The sintered mechanical properties, hardness, and fracture toughness, compare well against cemented carbides produced by powder metallurgy. Vickers hardness and fracture toughness (determined by the Palmquist method) are in the range HV30 1013-1292 and 17.0-19.2 MN·m-3/2, respectively.
We evaluated the wear properties under abrasion and erosion using the ASTM B611, ASTM G65, and ASTM G76 standard testing procedures. The wear resistance of the BJ3DP cemented carbide matches, and, in some cases, can exceed the resistance of conventionally produced cemented carbide.
We have manufactured components of varying geometric complexity with weights ranging from 0.53 g to 8 kg. BJ3DP enables the manufacture of components that are not feasible by pressing and sintering, even with extensive use of green machining.
10:50 HM 33
Microstructural Development in Binder Jet Additive Manufacturing of WC-Co
Prichard P.1, Wang Z.1, Miyanaji H.1
1Kennametal, Inc, USA
Cemented tungsten carbide is an important industrial material, which is typically manufactured into metal cutting tooling and wear components by conventional formative powder manufacturing processes.  However, complex cemented tungsten carbide components with unique features can be additively manufactured by the binder jetting process, which is more suitable than energy beam processes for producing non-weldable materials. The interrelationship between powder size and composition, print parameters, and sintering parameters are critical to the development of optimum microstructure and mechanical properties. The jetting of binder into a powder bed has been shown to introduce porosity due to powder particle ejection. Compensation for these large pores by increasing sintering temperature will result in excessive gain growth. This presentation will discuss the interaction between powder characteristics, print parameters, and sintering, which cooperate to determine the final microstructure and properties
11:10 HM 34
Effect of Thermal Post-treatment on Microstructure of Additively Manufactured Cemented Carbides
Fries S.1, Vogelpoth A.2, Kaletsch A.1, Weisheit A.2, Broeckmann C.1
1Institute for Materials Applications in Mechanical Engineering (IWM), RWTH Aachen University, Germany
2Fraunhofer Institute for Laser Technology (ILT), Germany
Laser based additive manufacturing of cemented carbides (WC-Co) remains challenging due to crack forming and residual porosity. Reduction of temperature gradients by high preheating temperature and successive thermal treatment are starting points for improving the quality of the additively manufactured parts. Thermal post-treatment is beneficial for final densification and homogenization of the microstructure. In this study, hot isostatic pressing (HIP) and Sinter-HIP are used for thermal post-treatment of the additive manufactured parts. Both methods use elevated temperature and pressure for densification. Compaction during the sinter HIP process is achieved by liquid phase sintering, while in the HIP process compaction is expected by lowering the yield strength of the material. Effect of these both mechanisms on carbide and binder phases is investigated in this study. Tungsten carbide grain size and shape, as well the composition of the binder phase are determined in as-built and thermal post-treated parts.
11:30 HM 35
Recent advances on the procesing of hardmetals by Solvent-on-Granules 3D-Printing
Carreño-Morelli E.1, Moseley S.2
1University of Applied Sciences and Arts Western Switzerland, Switzerland
2Hilti Corporation, Liechtenstein
Solvent-on Granules 3D-Printing grows green parts layer by layer by selectively dropping solvent on powder-polymer granule beds.
The solvent softens the polymer and the granules are pasted to each other. After solvent evaporation, the part is consolidated and further subjected to standard debinding and sintering in conventional furnaces.
WC-10Co parts have been processed from commercial powders. Final densification is achieved by hot isostatic pressing. Fully dense parts exhibit a microstructure meeting the standards of the classical press and sintering route. Shape preservation and tight tolerances are achieved in both simple test and complex geometry functional parts. Drill bits have been produced and tested for concrete percussion drilling.
11:50 HM 36
Bound Metal Deposition of Cemented Tungsten Carbide
Bose A.1, Reidy J.1, Jorgensen L.1, Tuncer N.1, Enneti R.2, Jewett T.2, Trasorras J.2, Wolfe T.2
1Desktop Metal, Inc., USA
2Global Tungsten & Powders, USA
Cemented Tungsten Carbide is a liquid phase sintered two-phase composite that exhibits high hardness, high wear and abrasion resistance resulting in the use of this material in numerous applications (cutting tools and wear components).   With the expanding application base for hardmetals, the demand for fabricating complex shaped components for prototyping and low volume serial production without any tooling has increased.  Additive Manufacturing (AM) has emerged as a process capable of rapidly fabricating complex shaped parts.  Among AM processes, Bound Metal Deposition (BMD) based on material extrusion, is capable of fabricating complex shaped hardmetal parts.  The processing steps having its roots in powder injection molding, include mixing the powder with an organic multicomponent binder to form a feedstock which is converted into precision rods that are used for material extrusion-based printing to form complex shaped green parts.  These green parts are solvent debound and sintered to fabricate the dense, complex shaped hardmetal parts.  This paper will discuss the BMD processing of a grade of hardmetal along with some of the microstructure and property development with sintering.
12:10 - 13:20
Lunch Break
Location: Walter Schwarzkopf Hall
13:20 - 14:50
Hard Materials - Microstructure
Location: Walter Schwarzkopf Hall
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13:20 HM 37
Approaching the 100th Anniversary of the Hardmetal Invention: From First WC-Co Samples towards Modern Advanced Hardmetal Grades - KEYNOTE
Konyashin I.1
1Element Six GmbH, Germany
The history of the invention of WC-Co hardmetals in the beginning of the 20’s of the last century is described. Information on the early production and development of hardmetals in Germany and other countries is given. Current range of advanced conventional and uncommon industrial hardmetal grades fabricated by different manufacturers is presented. General situation with respect to the fabrication of hardmetals and other hard materials in the USA, Europe and Asia is briefly described. Major modern trends in the research and development of novel hardmetals and new technologies for their manufacture as well as other hard and superhard materials are outlined. Recent results of basic research on simulations and examinations of the hardmetals’ structure on the micro-, nano- and atomic-level are presented. Novel techniques for in-situ examinations of deformation and thermal processes in WC-Co hardmetals in transmission and scanning electron microscopes are described.
13:50 HM 39
Back to the microscope: observations and insights into the process-microstructure-property relationships of WC-Co based cemented carbides
Ringer S.P.1, Primig S.2, Pachlhofer J.3, Czettl C.3
1The University of Sydney, Australia
2University of New South Wales, Australia
3CERATIZIT Austria GmbH, Austria
We have examined the microstructures in various WC-Co based cemented carbide insert materials with the aim of learning new insights into the process-microstructure-property relationships. Using a suite of advanced microscopy and microanalysis techniques, we have focussed on the phase types, fractions and compositions, crystallographic relationships and the interface composition and structure for various WC-binder phase composites. This presentation will summarise recent findings from our team’s multi-scale, multi-dimensional approach to microstructural characterisation. Topics covered will include our observation of Σ3-annealing twins in CoFCC grains that undergo an incomplete martensitic transformation to form CoHCP laths on cooling below TMs. There, we have shown that the parent CoFCC and product CoHCP phases are related via the Shoji-Nishiyama orientation relationship and that four variants of the CoHCP plates exhibit a special misorientation of 70.5±0.2°⟨112 ̅├ 0⟩┤. We relate the fraction transformed to binder content and WC grain size. We will also showcase observations of the atomic-scale microstructure that feature details of the W, C, Co and Ru atom distributions vary across the key phases of selected WC-Co materials.
14:10 HM 40
Neutron scattering studies of hard metals
Yildiz A.B.1, Norgren S.2, Hedström P.3
1KTH Royal Institute of Technology and Scatterin AB, Sweden
2Sandvik Coromant R&D and Lund University, Sweden
3KTH Royal Institute of Technology, Sweden
In-situ neutron scattering techniques enable monitoring of significantly larger sample volumes real-time in mimicked processing conditions. In the current study, we will demonstrate in two example cases how we combined in-house characterization and computational tools with the neutron scattering techniques to enhance the mechanistic understanding of nano- and microstructural evolution in hard metals and related systems. We will first present in-situ small-angle neutron scattering (SANS) experiments up to 1500 °C to unveil the evolution of nano-scale (V,W)Cx interface structures responsible for the grain coarsening inhibition in V-doped hard metals. We observe that (V,W)Cx interfacial layers present at liquid-phase sintering temperatures, and their size and volume fraction strongly depend on the presence of bulk (V,W)Cx precipitates and V activity in the binder phase. Second, we will show by in-situ neutron diffraction experiments during the aging of (Ti,Zr)C-based systems at 1600 °C how the small transition metal carbide additions affect the decomposition kinetics. Furthermore, we observe that whilst the composition of the ZrC-rich decomposition product remains unchanged, the TiC-rich phase attains its equilibrium composition over time.
14:30 HM 41
Liquid Phase Sintering of WC-Fe-Ni-Co-Cr cemented carbides: effect of WC powder particle size
Sánchez-Moreno J.M.1, Soria-Biurrun T.1, Lozada-Cabezas L.1, Navarrete-Cuadrado J.1, Ibarreta-Lopez F.2, Martinez-Pampliega R.2
Shrinkage, melting and degassing phenomena of WC-Fe-Ni-Co-Cr alloys during sintering were investigated by means of dilatometry, DSC and TGA techniques. Specimens with 20% vol. binder phase and a Fe/Ni/Co ratio of 40/40/20 in wt.%. were produced from WC-Fe-Ni-Co-(Cr3C2) powder mixtures. Results obtained with coarse and submicron WC powder grades were compared, taking into account that the latter were doped with Cr and V. C-windows and melting temperatures were accurately defined for coarse and fine grained microstructures with and without Cr3C2 additions. As described for WC-Co materials, significant shrinkage is found in submicron grades at temperatures well below their melting ranges, this effect being more pronounced as Cr content increases. As described for WC-Co-Cr materials, melting and solidification ranges are wider and displaced to lower temperatures as Cr content increases. Outgassing peaks are detected at temperatures compatible with carbothermal reduction of the different powder oxides. Some of these peaks are missing in submicron grades. Mechanical properties are within tolerances of those published for WC-Co materials if no secondary carbides are present in the microstructure.
14:50 - 15:10
Location: Walter Schwarzkopf Hall
15:10 - 16:50
Hard Materials - Characterization and testing
Location: Walter Schwarzkopf Hall
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15:10 HM 42
Aggressive High-Temperature Sliding Wear of WC and TiC7N3 Enhanced NbC Hardmetals
Genga R.1, Huang S.2, Vleugels J.2, Brandt G.3, Kelling N.3, Opitz C.3, Gradt T.3, Janse Van Vuuren A.4
1Academic Development Unit (ADU), University of the Witwatersrand; School of Mechanical, Industrial, and Aeronautical Engineering, University of the Witwatersrand; DST-NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, South Africa
2Department of Materials Engineering (MTM), KU Leuven, Belgium
3BAM Federal Institute for Materials Research and Testing, Germany
4CHRTEM, Nelson Mandela University, South Africa
In this study, effects of 0.8 - 4.0 wt% Cr3C2, TiC and Mo2C minor additions to WC and NbC hardmetals with alternative binders, and 14 - 20 wt% WC and TiC7N3 secondary-phase additions to conventionally (LPS) and rapidly sintered (PECS) NbC hardmetals were investigated in relation to microstructure, elastic modulus, thermal conductivity, and high temperature sliding wear. Additions WC and TiC7N3 to NbC hardmetals refined the microstructures and formed core – rim structured solid solutions, confirmed by annular dark-field (ADF) scanning transmission electron microscopy (STEM). High temperature sliding wear was conducted using a ball-on-disk tribometer at 700oC and 0% humidity, using Al2O3 balls and applying a 10 N force (>1.6 GPa Hertzian pressure), at a sliding speed of 1.17 m/s for 500 m. Generally, LPS WC and NbC hardmetals had lower sample wear rates (SWRs) and coefficients of friction (µ) than PECS materials. Additions of Mo2C and TiC to the WC hardmetals significantly reduced the SWR (~ 52%), while WC additions to NbC-TiC-Mo2C-12Ni reduced the SWRs. Conversely, TiC7N3 addition to NbC-TiC-Mo2C-12Ni had the opposite effect.
15:30 HM 43
Influence of corrosion-induced damage on mechanical integrity and load-bearing capability of cemented carbides
Llanes L.1, Zheng Y.1, Serra M.1, Fargas G.1, Armelin E.1, Lavigne O.2
1Universitat Politècnica de Catalunya, Spain
2Hyperion Materials & Technologies, Spain
WC-base cemented carbides, also referred to as hardmetals, have been the subject of intensive research and technological applications for past few decades. Several of these applications also include exposure to chemically aggressive media. Under these conditions, it has been shown that failure induced under applied load is accelerated, and corresponding service life may be significantly shortened. Within this context, this work addresses the influence of corrosion-induced damage on the mechanical integrity and load-bearing capability of cemented carbides with distinct microstructures at different length scales, i.e. from 100s nanometers to 1000s microns. Experimental data acquired by means of nanoindentation, pyramidal and spherical indentation as well as sliding contact (micro- and nanoscratch) techniques are presented. The study as a whole permits to point out guidelines for microstructural design of these materials under combined consideration of corrosion and mechanical contact as service-like conditions. It includes the assessment of the evolution of microstructure-property-performance interrelations due to the degradation of the material under severe working conditions.
15:50 HM 44
The spatial organization of corrosion products at the hardmetal/environment interface
De Gaudenzi G.P.1, Amati M.2, Gianoncelli A.2, Gregoratti L.2, Kiskinova M.2, Kourousias G.2, Tedeschi S.1, Bozzini B.3
1F.I.L.M.S. SpA - OMCD Group, Italy
2Elettra-Sincrotrone Trieste S.C.p.A., Italy
3Dept. of Energy, Politecnico di Milano, Italy
The behavior of hardmetal in chemically aggressive environments has been studied with various approaches. Although most of the work was mainly focused on the correlation between the environment and the performance of hardmetal grades with different composition, a close-knit group of studies concentrated on the assessment of the corrosion reaction mechanisms. Among the proposed models, the majority revolves around the phenomenological description of the so-called pseudo-passivation processes. Nonetheless, the molecular-level understanding of the phenomena occurring at the reaction interface is still limited. This work employed two synchrotron-based spectroscopies, Soft-X ray absorption Microspectroscopy (SXM) and Scanning PhotoElectron Microscopy (SPEM) to map the spatial distribution of elements and their chemical state with submicrometric lateral resolution. The coupling between WC and simple Co-base to complex (CoNiCrMo)-base metallic binders was considered at various pH values. The observed spatial organization of corrosion products enables the quantitative description of the formation of pseudo-passivating layers in terms of morphochemical coupling between phase-formation kinetics and selective binder corrosion, enabling the rationalization of the relative roles of environment pH value and binder composition.
16:10 HM 45
Further Wear Measurements on WC-Co Hardmetals
Gee M.1, Martensson M.2, Norgren S.2, Nunn J.1, Woolliams P.1, Timothy K.1
1National Physical Laboratory, United Kingdom
2Sandvik, Sweden
WC-Co hardmetals are used in many applications where resistance to wear is critical. This paper describes wear measurements using in situ measurement techniques.
Further experiments were made using the in situ SEM tribometer. The test system now gives real time quantitative measurement of the profile of repeated scratches made on WC-Co samples. Although the initial rate of damage was high, as the scratch developed and the applied pressure reduced, the rate of damage decreased.
Three different tests were also carried out with the NPL real-time in situ pin on disc system. WC-Co discs were tested against granite pins, Si3N4 balls in sliding wear tests, and against a Rockwell indenter in a rotating scratch test. The line-scan camera in the system was used to obtain a visual history of the dynamics of damage to the WC-Co discs. This was complemented by real time height maps of the wear obtained with a multi-point chromatic aberration probe.
The results from the real-time line-scan and profilometer sensors was backed up by post-test optical, SEM and FIB analysis.
16:30 HM 46
Temperature and strain-rate dependence of flow stress of WC-Co alloys under high temperature compressive deformation
Ichikawa R.1, Kawahara K.1, Igarashi M.1, Okada K.1
1Mitsubishi Materials Corporation, Japan
In order to understand the deformation mechanisms of WC-Co alloys at high temperature, the strain-rate sensitivity m and the activation volume v* were measured at strain rates between 10-3 s-1 and 10-4 s-1 and temperatures between 973 K and 1273 K with different grain sizes of WC.
For coarse-grained alloys, the deformation behavior did not change significantly in these test conditions.  Fine-grained alloys showed the similar deformation behavior to that of coarse-grained alloys in the high stress region, while in the low-stress region, as flow stress decreased, the m value increased markedly up to 0.2 and the v* value was reduced to 2b3 where b is the magnitude of the Burgers vector of WC.  The apparent activation energy showed that the rate-controlling process was mainly related to the WC phases.
It was concluded that the rate-controlling process for plastic deformation of the fine-grained alloys in the high-stress region and the coarse-grained alloys is the dislocation glide in WC phases, and that of fine-grained alloys in the low-stress region is the dislocation creep of WC phases.
16:50 - 16:50
End of sessions
Location: Walter Schwarzkopf Hall