- Email: [email protected]
Workshop charts cemented carbide advances
Sandik 35%
FIGURE 3: Market share for Indian hardmetal producers.
The papers presented in this workshop will be published later this year in a special issue of the journal Materials & Design published by Elsevier Science Ltd, Oxford, UK.
38 MPR October 2000
seems most likely that the dissolved W increases binder toughness by solid-solution strengthening. A separate presentation on recent advances in sintering of cemented carbides described a strategy to reduce the sintering time. Upadhyaya showed that the total cycle-time for consolidating metal cutting grades can be reduced by as much as 70% on an industrial scale through a fast dewaxingrapid sintering approach. Hardmetal sintering today is mostly performed under vacuum. However, the sintering-cycle adopted is a modified version of that used previously in reducing furnaces, and thus does not take full advantage of the improvements in furnace technology. A conventional industrial sintering operation for hardmetals takes about 15 h, with the cooling period an additional 5 h. A closer look reveals that it takes more than 8 h to dewax the hardmetal inserts (Figure 2). Most hardmetal powders contain ~3% wax. In comparison, most powder injection moulded (PIM) parts contain much higher levels (-40 ~01%) of the same organics, but are debound in less time. Typical cutting tool inserts are <2 cm3 in volume. Hence, it is hypothesized that using the same strategies as in PIM, the dewaxing time of cemented carbides can be greatly reduced. Thus, a new fast thermal cycle (Figure 2) was proposed for sintering cutting-tool grades, reducing the total sintering time to about 4 h. A reducing atmosphere is key to cutting the dewaxing time. Up to 600 “C, H, has no influence on WC, hence the
carbon-balance remains unaffected. Most cemented carbide manufacturers employ nonreducing atmosphere during dewaxing primarily because of safety concerns. In inert (argon) atmosphere, dewaxing is solely thermal. Compared to Ar, H, has significantly higher heat capacity and thermal conductivity, enhancing thermal dewaxing. H, also chemically interacts with the hydrocarbon constituents of the organic wax, promoting its catalytic removal, and thereby drastically reducing dewaxing time. Thus, a combination of fast dewaxing followed by a fast heating rate is the key to reducing the sir&ring time. Using the fast sintering approach, Upadhyaya successfully sintered a range of hardmetal compositions with up to 130 kg charge, corresponding to about 90% of the total furnace capacity. However, the non-uniform temperature distribution prevents the approach from being used for bigger parts.
The workshop culminated in round-table discussion kcused on the status of India’s hardmetal industry. Most players involved participated, with the notable exception of Sandvik (Asia). The Indian cutting tool and die/wear market is worth US$BO million. Figure 3 provides the breakdown of the market-share among the various companies. According to P.A. Kale of Electronica Machine Tool, Ltd, Nasik, “With recent economic liberalization, the Indian hardmetal scenario has entered a very competitive phase”. It has traditionally been dominated by Sandvik and WIDIA, which together account for 75% of the total market. Sandvik has a production facility in Pune. WIDIA has two plants in India, in Bangalore and Patencheru near Hyderabad, for processing metal-cutting and mining grades, respectively. Previously, one of the key impediments in India was a high tariff (-35%) on imports. This, and their wellestablished dealer networks,
gave Sandvik and WIDIA a virtual monopoly over the Indian market. New entrants were few and could not make effective inroads. For instance, Kennametal has two plants in India - one (40% stake with Birla) in Mumbai, and the second, a 50:50 partnership with Drillco, in Pune. However, even after a decade, the company has only a small presence in the Indian market. In the early 1990s the easing of duty restrictions gave a boost to free trade and opened the Indian economy. This led to a spurt of activities with several new players, such as Iscar, Sumitomo, Seco and Toshiba, entering the fray. Cheaper W and WC powders from China also became readily available to the Indian market. Consequently, WIDIA opted to import the powders, closing its ore-processing plant to reduce production costs. Iscar seems to be one of the winners from the present situation. Initially, its presence was limited to supplying imported inserts. However, its recent acquisition of Indicarb Ltd, Hosur, has doubled its market share to 10%. According to S. Chandra Narayanan, Executive Director, Indicarb, “Ordnance factories and automotive industries have traditionally been India’s main consumers for hardmetal products”. The demand from the defence establishment has stagnated over the years; since 1998, however, India’s automotive sector has seen an unprecedented 45% annual growth rate. Recently, several automotive companies have set up manufacturing bases in India. This is also contributing to the upbeat mood of the Indian hardmetal industry. Contact: Dr Anish Upadhyaya* Manager, R&D WIDIA (India) Ltd 8/9th Mile Tumkur Road Bangalore 560073, India. *Presently at the Dept of Materials & Metallurgical Engineering, IIT. Tel.: +91-5X-598559. Fax: +91-512-590260. E-mail: [email protected] ??
residual porosity, microstructure, grain size and grain boundaries in achieving the final properties.
Ferrous materials The topics covered ranged widely from the effects of porosity to the status of sintered component production. Prof. Paul Beiss (Aachen University of Technology, Germany) opened with a discussion of structure-property relationships in porous sintered steels. He amply demonstrated that average pore characteristics cannot be correlated with mechanical performances: fatigue fractures for instance are initiated only at large irregular pores, never at small round pores. He also presented some new results on the fully reversed flat bending fatigue data of sintered steels. Dr Herbert Danninger (Vienna University of Technology, Austria) examined processes in powder metal (PM) steel compacts during the initial stages of sintering, describing in depth the desorption of gases, reduction of surface oxides, neck formation and dissolution of carbon and other alloying elements in steels. In steel-graphite compacts the formation of stable necks is retarded until dissolution of graphite has occurred to a significant extent. In a second paper, Danninger further discussed the dissolution of different graphite grades during sintering of Fe-0.8%C steel, concluding that the selection of the graphite grade is important especially for presintering prior to further treatment. Prof. J.M. Torralba (Universidad Carlos III de Madrid, Spain) also gave two papers. The first on ‘Microstructural Evolution in HSS Parts Obtained by a Modified MIM Process’ highlighted the subtle differences between M2 and T15 high speed steels. In the second on the sinterability of the bronze and phosphorusbronze steels - detailed dilatometric studies were presented and a sintering temperature of 910 “C was found to be sufficient. The
range of ferrous alloy systems was overviewed by Dr. K.S. Narashiman (Hoeganaes Corp, Cinnaminson, USA) in his masterly paper ‘Transient Liquid Phase Sintering Application and Commercial Practice’. Sintered components provided the focus for Dr Akira Fujiki (NISSAN Motor, Japan), who detailed the present status and the future prospects of PM parts for automotive applications, and S.R. Sundaram (India), who gave a thorough review on sintered component production in Asia-Oceania.
Nonferrous and intermetallics Dr Graham Schaffer (University of Queensland, Australia) discussed the LPS of various aluminium alloys: the presence of magnesium reduces the surface oxide on aluminium particles, thus facilitating wetting and diffusion. Thermal barrier coatings of Ni-based superalloys via combustion synthesis/ sintering of powders were Prof. M.C. covered by Chaturvedi (University of Manitoba, Canada), while Prof. K.S. Hwang (National Taiwan University, Taipei) discussed sintering of MO with Ni and Co additives. Several papers considered tungsten-based systems. Dr Anish Upadhyaya discussed processing strategies for consolidating tungsten heavy alloys (WHAs) for ordnance applications, while Dr P. Ghosal of the Defence Metallurgical Research Lab (DMRL), Hyderabad, India, provided details of TEM investigations of LPS W-NiCo. No intermetallic phase was observed at the interface even at a very high magnification. Dr T.P. Bagchi of the DMRL detailed a case study on the sintering of WHA using various statistical problem-solving tools.
Ceramics The coverage of oxide ceramics included a lucid presentation from J. Lechelle (Direction des Reacteurs Nucleair, France) on the mechanism-based
approach to the sintering of MOX nuclear fuel, and a discussion from Dr D.K. Chatterjee (Eastman-Kodak Co, Rochester, USA) on the sintering behaviour and microstructure developments of alumina, zirconia and their composites. Moving to nonoxide ceramics, Prof. S. Somiya (University of Science and Technology, Tokyo, Japan) spoke on hydrothermal corrosion of S&N, and Sic, an important consideration for engine part applications. Prof. F. Thevenot (Ecole Nationale Superieure des Mines de Saint Etienne, emphasized the France) seeding of the powder in order to control microstructural features in the LPS of SIC!, with 3wt’% of eutectic composition (60% A&0,-40% Y,O,) as a sintering additive. Microstructure-property relationships in SIC ceramics LPS with oxynitride additives were considered by Dr G.R. Rixecker (Max-Planck Institut fur Metallforschung, Stuttgart Germany). Prof. M.P. Dariel (Ben-Gurion University, Israel) described different approaches - some relying on the variations of the sinterability of stacked powder layers - aimed at generating ceramic preforms with an in-built porosity gradient. SiAlON systems were considered by Dr S. Bandopadhyay (CGCRI, Calcutta, India) and Dr A.K. Jha (Regional Research Lab, Bhopal, India), while Dr T. Watanabe (Kyushu National Industrial Research Institute, Japan) discussed a new multilayer composite based on the A&O~iC/MoSi, - Mo2B, system, prepared by tape casting.
Cermets Microstructural development of both cemented carbides and cermets during sintering and heat-treatment was examined by Prof. H-O. Andren (Chalmers University of Technology, Goteborg, Sweden). He described how microscopic techniques like SEM and TEM, including energy filtered TEM, were successful in detailed structure studies of both hard and binder phases.
MPR October 2000
33
In another paper from Andren’s group, Robert Frykholm spoke on the microstructural development during gradient sintering of WC-TiC(C,N)-Co based cemented carbides. The material was sintered in a nitrogen-free atmosphere, resulting in an outward diffusion of nitrogen. Prof. S. Luyckx (South Africa) reviewed work done at the University of Witwatersrand on the effect of VC in WC-Co in amounts varying from 0.4-lOwt%. When added in amounts larger than lwt% it was found that VC is a useful substitute for WC. Dr Kenichi Takagi (Toy0 Kohan Co, Japan) covered high toughness boride-based cermets, describing how enhancing the reaction between the boride and metal matrix generates a ternary boride phase which is useful in tailoring the properties. Pradyot Datta (Indian Institute of Technology) presented an interesting paper
34
MPR October 2000
on the effect of CrB addition the sintering of on 316L/434L stainless steellOv/o Cr,C, composites, while Prof. G.S. Upadhyaya showed that the maximum value of transverse rupture strength for sintered porous cermets based on TiB, and TiB,-Tic-Mo,C was found for the TiB,-Tic-Mo,C40wt% Ni/Mn cermet. Dr S. Banerjee (Bhabha Atomic Research Centre, Mumbai, India) deviated from the strict domain of sintering to consider netshape forming of bi-continuous Also, composites (74vol% aAlsO,-26~01% Al(&)) by displacement reaction. The special feature was more or less isotropic linear shrinkage. The remaining sessions on electronic and magnetic materials included a discussion of recent developments in the sintering of NdFeB by B.E. Davis of the University of Birmingham, UK. The effect of composition on the densification kinetics was
described using a powder blending technique to vary the composition prior to sintering. The conference also provided the occasion for the release of Professor G.S. Upadhyaya’s book Sintered Metallic and Ceramic Materials (published by John Wiley, UK). Sintering 2000 was judged to have been a trendsetter in the new century, with participants agreeing that the quality of papers was high. It is hoped that future conferences in the series will maintain the same standard. next International The Conference, ‘Sintering 2004’, will most probably be organized in Israel. Contact: Professor G.S. Upadhyaya Department of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur 208 016, ?? India.
FIGURE 3: Market share for Indian hardmetal producers.
The papers presented in this workshop will be published later this year in a special issue of the journal Materials & Design published by Elsevier Science Ltd, Oxford, UK.
38 MPR October 2000
seems most likely that the dissolved W increases binder toughness by solid-solution strengthening. A separate presentation on recent advances in sintering of cemented carbides described a strategy to reduce the sintering time. Upadhyaya showed that the total cycle-time for consolidating metal cutting grades can be reduced by as much as 70% on an industrial scale through a fast dewaxingrapid sintering approach. Hardmetal sintering today is mostly performed under vacuum. However, the sintering-cycle adopted is a modified version of that used previously in reducing furnaces, and thus does not take full advantage of the improvements in furnace technology. A conventional industrial sintering operation for hardmetals takes about 15 h, with the cooling period an additional 5 h. A closer look reveals that it takes more than 8 h to dewax the hardmetal inserts (Figure 2). Most hardmetal powders contain ~3% wax. In comparison, most powder injection moulded (PIM) parts contain much higher levels (-40 ~01%) of the same organics, but are debound in less time. Typical cutting tool inserts are <2 cm3 in volume. Hence, it is hypothesized that using the same strategies as in PIM, the dewaxing time of cemented carbides can be greatly reduced. Thus, a new fast thermal cycle (Figure 2) was proposed for sintering cutting-tool grades, reducing the total sintering time to about 4 h. A reducing atmosphere is key to cutting the dewaxing time. Up to 600 “C, H, has no influence on WC, hence the
carbon-balance remains unaffected. Most cemented carbide manufacturers employ nonreducing atmosphere during dewaxing primarily because of safety concerns. In inert (argon) atmosphere, dewaxing is solely thermal. Compared to Ar, H, has significantly higher heat capacity and thermal conductivity, enhancing thermal dewaxing. H, also chemically interacts with the hydrocarbon constituents of the organic wax, promoting its catalytic removal, and thereby drastically reducing dewaxing time. Thus, a combination of fast dewaxing followed by a fast heating rate is the key to reducing the sir&ring time. Using the fast sintering approach, Upadhyaya successfully sintered a range of hardmetal compositions with up to 130 kg charge, corresponding to about 90% of the total furnace capacity. However, the non-uniform temperature distribution prevents the approach from being used for bigger parts.
The workshop culminated in round-table discussion kcused on the status of India’s hardmetal industry. Most players involved participated, with the notable exception of Sandvik (Asia). The Indian cutting tool and die/wear market is worth US$BO million. Figure 3 provides the breakdown of the market-share among the various companies. According to P.A. Kale of Electronica Machine Tool, Ltd, Nasik, “With recent economic liberalization, the Indian hardmetal scenario has entered a very competitive phase”. It has traditionally been dominated by Sandvik and WIDIA, which together account for 75% of the total market. Sandvik has a production facility in Pune. WIDIA has two plants in India, in Bangalore and Patencheru near Hyderabad, for processing metal-cutting and mining grades, respectively. Previously, one of the key impediments in India was a high tariff (-35%) on imports. This, and their wellestablished dealer networks,
gave Sandvik and WIDIA a virtual monopoly over the Indian market. New entrants were few and could not make effective inroads. For instance, Kennametal has two plants in India - one (40% stake with Birla) in Mumbai, and the second, a 50:50 partnership with Drillco, in Pune. However, even after a decade, the company has only a small presence in the Indian market. In the early 1990s the easing of duty restrictions gave a boost to free trade and opened the Indian economy. This led to a spurt of activities with several new players, such as Iscar, Sumitomo, Seco and Toshiba, entering the fray. Cheaper W and WC powders from China also became readily available to the Indian market. Consequently, WIDIA opted to import the powders, closing its ore-processing plant to reduce production costs. Iscar seems to be one of the winners from the present situation. Initially, its presence was limited to supplying imported inserts. However, its recent acquisition of Indicarb Ltd, Hosur, has doubled its market share to 10%. According to S. Chandra Narayanan, Executive Director, Indicarb, “Ordnance factories and automotive industries have traditionally been India’s main consumers for hardmetal products”. The demand from the defence establishment has stagnated over the years; since 1998, however, India’s automotive sector has seen an unprecedented 45% annual growth rate. Recently, several automotive companies have set up manufacturing bases in India. This is also contributing to the upbeat mood of the Indian hardmetal industry. Contact: Dr Anish Upadhyaya* Manager, R&D WIDIA (India) Ltd 8/9th Mile Tumkur Road Bangalore 560073, India. *Presently at the Dept of Materials & Metallurgical Engineering, IIT. Tel.: +91-5X-598559. Fax: +91-512-590260. E-mail: [email protected] ??
residual porosity, microstructure, grain size and grain boundaries in achieving the final properties.
Ferrous materials The topics covered ranged widely from the effects of porosity to the status of sintered component production. Prof. Paul Beiss (Aachen University of Technology, Germany) opened with a discussion of structure-property relationships in porous sintered steels. He amply demonstrated that average pore characteristics cannot be correlated with mechanical performances: fatigue fractures for instance are initiated only at large irregular pores, never at small round pores. He also presented some new results on the fully reversed flat bending fatigue data of sintered steels. Dr Herbert Danninger (Vienna University of Technology, Austria) examined processes in powder metal (PM) steel compacts during the initial stages of sintering, describing in depth the desorption of gases, reduction of surface oxides, neck formation and dissolution of carbon and other alloying elements in steels. In steel-graphite compacts the formation of stable necks is retarded until dissolution of graphite has occurred to a significant extent. In a second paper, Danninger further discussed the dissolution of different graphite grades during sintering of Fe-0.8%C steel, concluding that the selection of the graphite grade is important especially for presintering prior to further treatment. Prof. J.M. Torralba (Universidad Carlos III de Madrid, Spain) also gave two papers. The first on ‘Microstructural Evolution in HSS Parts Obtained by a Modified MIM Process’ highlighted the subtle differences between M2 and T15 high speed steels. In the second on the sinterability of the bronze and phosphorusbronze steels - detailed dilatometric studies were presented and a sintering temperature of 910 “C was found to be sufficient. The
range of ferrous alloy systems was overviewed by Dr. K.S. Narashiman (Hoeganaes Corp, Cinnaminson, USA) in his masterly paper ‘Transient Liquid Phase Sintering Application and Commercial Practice’. Sintered components provided the focus for Dr Akira Fujiki (NISSAN Motor, Japan), who detailed the present status and the future prospects of PM parts for automotive applications, and S.R. Sundaram (India), who gave a thorough review on sintered component production in Asia-Oceania.
Nonferrous and intermetallics Dr Graham Schaffer (University of Queensland, Australia) discussed the LPS of various aluminium alloys: the presence of magnesium reduces the surface oxide on aluminium particles, thus facilitating wetting and diffusion. Thermal barrier coatings of Ni-based superalloys via combustion synthesis/ sintering of powders were Prof. M.C. covered by Chaturvedi (University of Manitoba, Canada), while Prof. K.S. Hwang (National Taiwan University, Taipei) discussed sintering of MO with Ni and Co additives. Several papers considered tungsten-based systems. Dr Anish Upadhyaya discussed processing strategies for consolidating tungsten heavy alloys (WHAs) for ordnance applications, while Dr P. Ghosal of the Defence Metallurgical Research Lab (DMRL), Hyderabad, India, provided details of TEM investigations of LPS W-NiCo. No intermetallic phase was observed at the interface even at a very high magnification. Dr T.P. Bagchi of the DMRL detailed a case study on the sintering of WHA using various statistical problem-solving tools.
Ceramics The coverage of oxide ceramics included a lucid presentation from J. Lechelle (Direction des Reacteurs Nucleair, France) on the mechanism-based
approach to the sintering of MOX nuclear fuel, and a discussion from Dr D.K. Chatterjee (Eastman-Kodak Co, Rochester, USA) on the sintering behaviour and microstructure developments of alumina, zirconia and their composites. Moving to nonoxide ceramics, Prof. S. Somiya (University of Science and Technology, Tokyo, Japan) spoke on hydrothermal corrosion of S&N, and Sic, an important consideration for engine part applications. Prof. F. Thevenot (Ecole Nationale Superieure des Mines de Saint Etienne, emphasized the France) seeding of the powder in order to control microstructural features in the LPS of SIC!, with 3wt’% of eutectic composition (60% A&0,-40% Y,O,) as a sintering additive. Microstructure-property relationships in SIC ceramics LPS with oxynitride additives were considered by Dr G.R. Rixecker (Max-Planck Institut fur Metallforschung, Stuttgart Germany). Prof. M.P. Dariel (Ben-Gurion University, Israel) described different approaches - some relying on the variations of the sinterability of stacked powder layers - aimed at generating ceramic preforms with an in-built porosity gradient. SiAlON systems were considered by Dr S. Bandopadhyay (CGCRI, Calcutta, India) and Dr A.K. Jha (Regional Research Lab, Bhopal, India), while Dr T. Watanabe (Kyushu National Industrial Research Institute, Japan) discussed a new multilayer composite based on the A&O~iC/MoSi, - Mo2B, system, prepared by tape casting.
Cermets Microstructural development of both cemented carbides and cermets during sintering and heat-treatment was examined by Prof. H-O. Andren (Chalmers University of Technology, Goteborg, Sweden). He described how microscopic techniques like SEM and TEM, including energy filtered TEM, were successful in detailed structure studies of both hard and binder phases.
MPR October 2000
33
In another paper from Andren’s group, Robert Frykholm spoke on the microstructural development during gradient sintering of WC-TiC(C,N)-Co based cemented carbides. The material was sintered in a nitrogen-free atmosphere, resulting in an outward diffusion of nitrogen. Prof. S. Luyckx (South Africa) reviewed work done at the University of Witwatersrand on the effect of VC in WC-Co in amounts varying from 0.4-lOwt%. When added in amounts larger than lwt% it was found that VC is a useful substitute for WC. Dr Kenichi Takagi (Toy0 Kohan Co, Japan) covered high toughness boride-based cermets, describing how enhancing the reaction between the boride and metal matrix generates a ternary boride phase which is useful in tailoring the properties. Pradyot Datta (Indian Institute of Technology) presented an interesting paper
34
MPR October 2000
on the effect of CrB addition the sintering of on 316L/434L stainless steellOv/o Cr,C, composites, while Prof. G.S. Upadhyaya showed that the maximum value of transverse rupture strength for sintered porous cermets based on TiB, and TiB,-Tic-Mo,C was found for the TiB,-Tic-Mo,C40wt% Ni/Mn cermet. Dr S. Banerjee (Bhabha Atomic Research Centre, Mumbai, India) deviated from the strict domain of sintering to consider netshape forming of bi-continuous Also, composites (74vol% aAlsO,-26~01% Al(&)) by displacement reaction. The special feature was more or less isotropic linear shrinkage. The remaining sessions on electronic and magnetic materials included a discussion of recent developments in the sintering of NdFeB by B.E. Davis of the University of Birmingham, UK. The effect of composition on the densification kinetics was
described using a powder blending technique to vary the composition prior to sintering. The conference also provided the occasion for the release of Professor G.S. Upadhyaya’s book Sintered Metallic and Ceramic Materials (published by John Wiley, UK). Sintering 2000 was judged to have been a trendsetter in the new century, with participants agreeing that the quality of papers was high. It is hoped that future conferences in the series will maintain the same standard. next International The Conference, ‘Sintering 2004’, will most probably be organized in Israel. Contact: Professor G.S. Upadhyaya Department of Materials and Metallurgical Engineering, Indian Institute of Technology, Kanpur 208 016, ?? India.