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German hardmetal group picks fruits of research success
special feature
German hardmetal group picks fruits of research success Collaboration between members is a key attribute of the Fachverband Pulvermetallurgie, the German association for the PM industry, in pushing back the frontiers of knowledge...
T
he Hardmetal Working Group (Arbeitkreis Hartmetall) of the German Fachverband Pulvermetallurgie (FPM) has released details of three recently completed collaborative research projects that it states have already reaped practical benefits for participating FPM members. According to Hans Kolaska, leader of the FPM sectoral group and initiator of a wide range of R&D projects in the hardmetals sector over the past 15 years, the three projects represent only a small part of the total effort of the Hardmetal Group, which incorporates members from Germany, Austria, Switzerland and Luxembourg. He said that funding for the research, which is mainly carried out in specialised research institutes and university departments, is exclusively provided by the participating members of the group. The results are subsequently only available free of charge to partners, to implement and exploit as they see fit.
and at the same time enhance environmental protection and eliminate the need for costly explosion prevention. The work was undertaken at the Fraunhofer-IKTS (Institute for Ceramic and Sintering Materials) in Dresden, under the direction of Dr Manfred Nebelung and resulted in a patent common to all participants.
Improved CVD Coatings
Water technology for WC-Co Powder Environmental improvement is seen as a “must do” for industry, and powder metallurgy is no exception Lessening reliance on organic solvents and eliminating an explosion hazard was the focus of one of the projects. The work was centred around introducing water as a replacement for acetone, hexane, heptane or alcohol used in the milling and granulation of WC-Co powders. The target was to replace the volatile and explosive milling solvents used previously,
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MPR November 2006
to avoid excessive oxygen pickup in the milled WC-Co powders. The milled powder could then be spray dried in air and hot drying gas to produce a homogeneous granulate with good flowability (Figure 1), making them suitable for use in automated powder presses, as well as giving a very good hardmetal structure. They also investigated new binder components that showed improved compressibility in comparison to conventional paraffins. Tests at the members’ plants have been positive, and there are plans to transfer the new technology into production.
Figure 1. WC-Co ready-to-press granulate produced by milling in water as against conventional solvents.
Dr Nebelung and his researchers investigated three WC-Co mixtures of different primary grain sizes and compositions. They added a new dispersant and passivating agent to the water used in milling and also adapted the milling conditions so as
A further project undertaken at Fraunhofer-IKTS in Dresden involved the development of improved Ti1-xAlxN coatings for cutting tools by chemical vapour deposition (CVD). This was tested against physical vapour deposition (PVD), which is the current method normally used in industrial production for this type of coating. According to project leader Dr Ingolf Endler, when using PVD, the aluminium/titanium ratio of 3:1 cannot be exceeded as the coatings become soft and consist predominantly of hexagonal AlN. His research group developed a novel CVD process whereby Ti1-xAlxN coatings with aluminium/titanium ratios of 4:1 to 9:1 could be produced. They also give improved oxidation resistance of the coating, in addition to high hardness of 33 up to 40 GPa and Young’s modulus of 440 up to 540 GPa. These values are considerably higher than those achieved by PVD Ti1-xAlxN coatings. An application for patents has been made.
0026-0657/06 ©2006 Elsevier Ltd. All rights reserved.
Carbide phases such as TaC, VC und Cr3C2 are important dopant constituents in hardmetals, providing uniform microstructure and serving as graingrowth inhibitors. Professor Walter Lengauer and his Physical Metallurgy Research Group at the Vienna University of Technology, have been studying the influence of various carbide dopants in the form of single carbide phase additions, as well as combinations on the microstructure and properties of WC-10%Co fine-grained hardmetals. In the first part of this cooperative FPM Hardmetal Group study, the solubility limit of various dopants in the Co binder phase was investigated at both low and high carbon levels. Grain growth distribution This was performed by preparation of model alloys containing WC, Co, the various combinations doping carbides as well as free carbon or eta-phases, respectively. The alloys were examined by high-performance electron probe microanalysis of polished samples. They were also examined by optical emission spectroscopy of dissolved binder phase. Starting from the data obtained in this step, WC-10%Co hardmetals with high and low carbon balance were prepared with a doping content just below the solubility limit of the various dopants in the binder phase. The alloys
were sintered at 1430°C and examined for the activity of grain growth inhibitors of the various combinations by using various sintering dwells at the vertex temperature. Further data on coercive force, magnetic saturation, Palmqvist fracture toughness and Vickers hardness were collected from all alloys. Establishing the bending Figure 2. Fracture surface of a hardmetal cutting tool coated strength as a function of with the new Ti1-xAlxN CVD coating. dopant combination, each with high and low carbon levels, bars related research projects are nearing were sintered, ground, tested, and the completion by the FPM working group. data was subjected to Weibull statistics. These include: For some of the dopant combina• ‘Gas atmospheres’ (leader: Dr Tim tions, the bending strength as well as Gestrich – Fraunhofer-IKTS, Dresden); the Weibull parameter (a measure for • ‘Hard turning and supersonic machinthe reliability), could be substantially ing – innovative processes for machining enhanced at the same time. The upper hardmetals’ (leader: Andreas Weber – IPT values were 4700 N/mm2 (4,7 GPa) for a Aachen), • ‘RF-plasma synthesis of hard mateWeibull factor of m=60 (Fig.5). The final step of this research is rial nano particles’ (leader: Dr Marc devoted to the effect of using recycled Leparoux, EPMA Thun) • ‘Diamond-coatings suitable for powder on the microstructure and properties. Two different levels of recycling hardmetals’ (Leader: R. Fritsch – WZL powder content added to the starting for- Aachen) mulation are being investigated. Further examinations will include grain-growth Further information can be distribution analysis and influence of obtained by contacting: Hans Kolaska, sintering temperature on the microstrucFachverband Pulvermetallurgie, ture and properties. Goldene Pforte 1, 58093 Hagen, Hans Kolaska told Metal Powder Germany. Tel: +49 2331 958817; email: Report that several other [email protected]
Figure 3. EDX X-ray spectroscopy of composition of CVD aluminium-rich Ti1-xAlxN coating.
Figure 4. Wear test against Ck45 steel shows 30% lower wear of the new CVD Ti-AlN coatings compared with similar coating by PVD.
metal-powder.net
Figure 5. Weibull plot for hardmetals with varying doping elements in form of carbide phases. Both high TRS and high reliability (slope of the line) could be successively achieved by appropriate amounts and combinations of carbide phases and adjustment of the carbon balance (blue data points and line).
November 2006 MPR
29
German hardmetal group picks fruits of research success Collaboration between members is a key attribute of the Fachverband Pulvermetallurgie, the German association for the PM industry, in pushing back the frontiers of knowledge...
T
he Hardmetal Working Group (Arbeitkreis Hartmetall) of the German Fachverband Pulvermetallurgie (FPM) has released details of three recently completed collaborative research projects that it states have already reaped practical benefits for participating FPM members. According to Hans Kolaska, leader of the FPM sectoral group and initiator of a wide range of R&D projects in the hardmetals sector over the past 15 years, the three projects represent only a small part of the total effort of the Hardmetal Group, which incorporates members from Germany, Austria, Switzerland and Luxembourg. He said that funding for the research, which is mainly carried out in specialised research institutes and university departments, is exclusively provided by the participating members of the group. The results are subsequently only available free of charge to partners, to implement and exploit as they see fit.
and at the same time enhance environmental protection and eliminate the need for costly explosion prevention. The work was undertaken at the Fraunhofer-IKTS (Institute for Ceramic and Sintering Materials) in Dresden, under the direction of Dr Manfred Nebelung and resulted in a patent common to all participants.
Improved CVD Coatings
Water technology for WC-Co Powder Environmental improvement is seen as a “must do” for industry, and powder metallurgy is no exception Lessening reliance on organic solvents and eliminating an explosion hazard was the focus of one of the projects. The work was centred around introducing water as a replacement for acetone, hexane, heptane or alcohol used in the milling and granulation of WC-Co powders. The target was to replace the volatile and explosive milling solvents used previously,
28
MPR November 2006
to avoid excessive oxygen pickup in the milled WC-Co powders. The milled powder could then be spray dried in air and hot drying gas to produce a homogeneous granulate with good flowability (Figure 1), making them suitable for use in automated powder presses, as well as giving a very good hardmetal structure. They also investigated new binder components that showed improved compressibility in comparison to conventional paraffins. Tests at the members’ plants have been positive, and there are plans to transfer the new technology into production.
Figure 1. WC-Co ready-to-press granulate produced by milling in water as against conventional solvents.
Dr Nebelung and his researchers investigated three WC-Co mixtures of different primary grain sizes and compositions. They added a new dispersant and passivating agent to the water used in milling and also adapted the milling conditions so as
A further project undertaken at Fraunhofer-IKTS in Dresden involved the development of improved Ti1-xAlxN coatings for cutting tools by chemical vapour deposition (CVD). This was tested against physical vapour deposition (PVD), which is the current method normally used in industrial production for this type of coating. According to project leader Dr Ingolf Endler, when using PVD, the aluminium/titanium ratio of 3:1 cannot be exceeded as the coatings become soft and consist predominantly of hexagonal AlN. His research group developed a novel CVD process whereby Ti1-xAlxN coatings with aluminium/titanium ratios of 4:1 to 9:1 could be produced. They also give improved oxidation resistance of the coating, in addition to high hardness of 33 up to 40 GPa and Young’s modulus of 440 up to 540 GPa. These values are considerably higher than those achieved by PVD Ti1-xAlxN coatings. An application for patents has been made.
0026-0657/06 ©2006 Elsevier Ltd. All rights reserved.
Carbide phases such as TaC, VC und Cr3C2 are important dopant constituents in hardmetals, providing uniform microstructure and serving as graingrowth inhibitors. Professor Walter Lengauer and his Physical Metallurgy Research Group at the Vienna University of Technology, have been studying the influence of various carbide dopants in the form of single carbide phase additions, as well as combinations on the microstructure and properties of WC-10%Co fine-grained hardmetals. In the first part of this cooperative FPM Hardmetal Group study, the solubility limit of various dopants in the Co binder phase was investigated at both low and high carbon levels. Grain growth distribution This was performed by preparation of model alloys containing WC, Co, the various combinations doping carbides as well as free carbon or eta-phases, respectively. The alloys were examined by high-performance electron probe microanalysis of polished samples. They were also examined by optical emission spectroscopy of dissolved binder phase. Starting from the data obtained in this step, WC-10%Co hardmetals with high and low carbon balance were prepared with a doping content just below the solubility limit of the various dopants in the binder phase. The alloys
were sintered at 1430°C and examined for the activity of grain growth inhibitors of the various combinations by using various sintering dwells at the vertex temperature. Further data on coercive force, magnetic saturation, Palmqvist fracture toughness and Vickers hardness were collected from all alloys. Establishing the bending Figure 2. Fracture surface of a hardmetal cutting tool coated strength as a function of with the new Ti1-xAlxN CVD coating. dopant combination, each with high and low carbon levels, bars related research projects are nearing were sintered, ground, tested, and the completion by the FPM working group. data was subjected to Weibull statistics. These include: For some of the dopant combina• ‘Gas atmospheres’ (leader: Dr Tim tions, the bending strength as well as Gestrich – Fraunhofer-IKTS, Dresden); the Weibull parameter (a measure for • ‘Hard turning and supersonic machinthe reliability), could be substantially ing – innovative processes for machining enhanced at the same time. The upper hardmetals’ (leader: Andreas Weber – IPT values were 4700 N/mm2 (4,7 GPa) for a Aachen), • ‘RF-plasma synthesis of hard mateWeibull factor of m=60 (Fig.5). The final step of this research is rial nano particles’ (leader: Dr Marc devoted to the effect of using recycled Leparoux, EPMA Thun) • ‘Diamond-coatings suitable for powder on the microstructure and properties. Two different levels of recycling hardmetals’ (Leader: R. Fritsch – WZL powder content added to the starting for- Aachen) mulation are being investigated. Further examinations will include grain-growth Further information can be distribution analysis and influence of obtained by contacting: Hans Kolaska, sintering temperature on the microstrucFachverband Pulvermetallurgie, ture and properties. Goldene Pforte 1, 58093 Hagen, Hans Kolaska told Metal Powder Germany. Tel: +49 2331 958817; email: Report that several other [email protected]
Figure 3. EDX X-ray spectroscopy of composition of CVD aluminium-rich Ti1-xAlxN coating.
Figure 4. Wear test against Ck45 steel shows 30% lower wear of the new CVD Ti-AlN coatings compared with similar coating by PVD.
metal-powder.net
Figure 5. Weibull plot for hardmetals with varying doping elements in form of carbide phases. Both high TRS and high reliability (slope of the line) could be successively achieved by appropriate amounts and combinations of carbide phases and adjustment of the carbon balance (blue data points and line).
November 2006 MPR
29