wc grain growth and grain growth inhibition in nickel and iron binder hardmetals

WC grain growth and grain growth inhibition in nickeland iron binder hardmetals

Bernhard Wittmann, Wolf-Dieter Schubert *, Benno Lux

Institute for Chemical Technology of Inorganic Materials, Vienna University of Technology, A-1060 Vienna, Austria

Received 20 September 2001

Abstract

WC grain growth and growth inhibition of an 0.6 lm FSSS WC powder (average SEM size: 0.35 lm) were studied in WC–10

wt% Ni alloys by adding 0–2 wt% of inhibitor carbides (VC, Cr3C2, TaC, TiC and ZrC).

Alloy gross carbon content turned out to be a crucial factor for WC growth in Ni alloys, even with high inhibitor additions.

Coarsening was more pronounced in high carbon alloys, compared with low carbon grades, resulting in a significantly lower

hardness. VC proved to be by far the most effective grain growth inhibitor in WC–Ni hardmetals, followed by TaC, Cr3C2, TiC and

ZrC. Hardness increased with increasing amount of additive but reached a maximum above which it remained about the same.

Experiments on WC–Fe–(VC) alloys revealed that WC grain growth is strongly restricted in Fe-binder alloys, even without

additions of growth inhibitors.

Binder chemistry thus strongly influences both continuous and discontinuous WC grain growth. This chemistry is determined by

the nature of the binder matrix (Fe, Co, Ni), the alloy gross carbon content (which determines the composition of the binder matrix)

as well as the inhibitor additive. � 2002 Elsevier Science Ltd. All rights reserved.

Keywords: Hardmetal; Alternative binder; WC grain growth; WC grain growth inhibition

1. Introduction

For the production of hardmetals tungsten carbide(WC) is the basic and most widely used hard compound,whereas cobalt was found to be the optimal binder metalfor most applications. Other iron group metals (nickeland iron) are employed only to a limited extent forspecialized applications, e.g. where hot hardness andresistance against thermal cracking or corrosion/oxida-tion resistance are required [1,2]. Compared with theWC–Co system, which has been extensively investigatedin the past due to its commercial importance, there isstill limited information on alternative binders.

Up to now, for example, no systematic study has beenperformed on WC grain growth and growth inhibitionin these systems. Thus it appeared to be worthwhile tocarry out a respective investigation, and to compare theresults on WC grain growth and growth inhibition with

those already known from the well-investigated WC–Cosystem [3].

WC grain growth and grain growth inhibition wereinvestigated using a straight WC–10 wt% Ni grade andadditions of small amounts of inhibitor carbides (VC,Cr3C2, TaC, TiC, ZrC); as is the practice in the manu-facture of fine-grained WC–Co hardmetals. WC graincoarsening in a WC–10 wt% Fe alloy was additionallyinvestigated.

2. Literature

Little has been reported on WC grain growth andgrowth inhibition in WC–Ni alloys. No direct evidencewas found in the related literature on grain growth inunalloyed WC–Ni. However, the early results of Suzukiand Yamamoto [4] demonstrated a strong influence ofthe carbon content on the hardness of the sintered ma-terial. For a WC–10 wt% Ni alloy, the hardness variedbetween �1060 HV30 for a high carbon alloy and�1280 HV30 for a low carbon alloy, indicating a strongimpact of binder chemistry on WC grain coarsening.

International Journal of Refractory Metals & Hard Materials 20 (2002) 51–60

www.elsevier.com/locate/ijrmhm

*Corresponding author. Tel.: +43-1-58801-16-126; fax: +43-1-

58801-16-199.

E-mail address: [email protected] (W.-D. Schubert).

0263-4368/02/$ - see front matter � 2002 Elsevier Science Ltd. All rights reserved.

PII: S0263-4368 (01 )00070-1

Excessive grain growth was observed in WC–6 wt% Nialloys at 1500 �C with a plain nickel binder [5]. Bothchromium and molybdenum were found to act as graingrowth inhibitors [5,6], but no systematic data wereavailable on the inhibiting effect. Alloying additions ofV, Mo and Cr were observed to increase the hardness inFe–Co–Ni-bonded hardmetals, and VC was found to bethe most effective grain growth inhibitor, as it is in theWC–Co system [3]. Data for the solubility of VC, Cr3C2,TaC, NbC, TiC and ZrC in nickel are scarce [7].

3. Experimental

3.1. Starting materials

High purity starting materials (WC, Ni, Fe) wereused for the preparation of alloys. A SEM image of theWC powder used is presented in Fig. 1.

3.2. Alloy preparation

(90� x) wt% WC, 10 wt% Ni and x wt% inhibitorcarbide were immersed in cyclohexane and either ballmilled for 72 h (steel lining, 60% of the critical rotationspeed) or attritor milled for 2 h (700 rpm, plate stirrer). 2wt% wax was added as a pressing aid. Different amountsof carbon black were added to the individual batches inorder to obtain the desired gross carbon content of thealloys. After milling, the cyclohexane was evaporated

using a Rotavapor. The powder mix was passed througha 0.5 mm sieve and subsequently granulated in a Tur-bula Mixer for 10 min to obtain a smoothly flowinggranulate. 11 g of this granulate were pressed in ahydraulic press at 200 MPa to bars of 6� 5� 50 mm3.

3.3. Sintering

Sintering was carried out in an industrial GCA vac-uum furnace for 1 h at 1480 �C (1 h at 1350 �C in case ofthe iron alloys). The heating rate was 10 �C/min in thetemperature range to 1250 �C, and 3 �C/min above. Thetotal pressure was < 0:01 mbar.

The samples were sintered in graphite boats withribbed bottoms. In order to achieve alloys with highgross carbon content (graphite precipitation) some ofthe samples were covered with graphite or carbon black.

The boats were covered with a graphite plate in orderto create a micro-atmosphere whose carbon potential isdominated mainly by the alloys and not by the degassingof the carbon felt or by small furnace leakages.

3.4. Vickers hardness measurement and microscopicinvestigations

The sintered samples were cut with a diamond saw,embedded in Bakelite�, ground and mirror polishedwith diamond suspensions. Vickers indentations werecarried out on a hardness tester M4U 025 by EMCO(Austria).

Fig. 1. SEM image of the WC powder used for this investigation; grain size: 0.35 lm (estimated by SEM-image analysis) calculated diameter from

BET: 0.2 lm; magnification: 20000�.

52 B. Wittmann et al. / International Journal of Refractory Metals & Hard Materials 20 (2002) 51–60

An indenter load of 30 kgf was used for indentation,as recommended by ISO 3878. SEM imaging was per-formed on etched sections (Murakami solution; �5 min)using a JEOL 6400 electron microscope.

4. Results

Table 1 presents an overview of the sinteringexperiments. Both two-phase (WCþNi) as well asthree-phase alloys (WCþNiþ g and WCþNiþ C,respectively) were investigated, to consider the influenceof the alloy gross carbon content on the growth process.

Table 1 also summarizes the results of the hardnessmeasurements that give a first indication of the efficiencyof the growth inhibition.

4.1. WC grain growth in undoped (inhibitor free) WC–Nialloys

SEM images of an undoped high carbon and lowcarbon alloy are presented in Fig. 2. From this com-parison it can be seen that the alloy gross carbon contentexerts a considerable influence on WC grain growth.Strong grain growth occurred in the high carbon alloy(HV30: 1032); whereas a very non-uniform but signifi-cantly finer microstructure was formed in case of the lowcarbon grade (HV30: 1403).

This characteristic difference in grain growth alreadydevelops during the heating-up of the sintering cycle, ascan be demonstrated by interrupted sintering experi-ments, where the samples were cooled down immedi-ately after heating to 1480 �C (Fig. 3). On isothermalliquid phase sintering, only limited further WC graingrowth occurred, shifting the average grain size tohigher values. While, in case of the low carbon alloy asignificant part of the fine-grained portion survived theisothermal sintering, most of it disappeared in the high

carbon alloy by dissolution of the finer particles andgrowth of the larger (Ostwald ripening).

4.2. WC grain growth in doped WC–Ni alloys

4.2.1. VC-doped alloysVC proved to be by far the most effective grain

growth inhibitor in WC–Ni alloys. The strong growthinhibiting effect can be deduced from Fig. 4, whichshows a considerable hardness increase with increasingVC additions, corresponding to the decrease in WCgrain size (Fig. 5).

Table 1

Overview on sintering experiments and HV 30 values of the respective

alloysa

WC–10 Ni Containing

g-phasesTwo-phase:

WC–10 Ni

Graphite

precipitation

HV 30: 1403 1032 1000

VC (in %)

0.2 1585 1582 1308

0.5 1574 1649 1464

1.0 1826 1879 1630

2.0 1738 1802 1699

Cr3C2 (in %)

0.2 1355 1383 1201

0.5 1480 1490 1405

1.0 1591 1580 1463

2.0 1574 1504 1467

TaC (in %)

0.2 1377 1012 935

1.0 1593 1615 1506

TiC (in %)

0.2 1589 1373 1187

1.0 1405 1370 1290

ZrC (in %)

0.2 1554 1116 1047

1.0 1512 1357 1023a Sintered at 1480 �C for 1 h.

Fig. 2. SEM images of microstructures of WC–10 wt% Ni l.c. (left) and h.c. alloy (right); 2000�.

B. Wittmann et al. / International Journal of Refractory Metals & Hard Materials 20 (2002) 51–60 53

High carbon alloys always showed a significantlylower hardness than their low carbon variants, even withhigh VC additions.

1 wt% VC turned out to be the most efficient additive,leading to a high hardness, and a high degree of mi-crostructural uniformity. No WC grains larger than1 lm were detected in this alloy. At higher additions (2wt% VC), no further increase in hardness was observedin two-phase alloys, but nest-like precipitates of (V,W)C occurred.

4.2.2. Cr3C2-doped alloysThe influence of Cr3C2-additions on the WC grain

growth was less pronounced than that of VC in termsof hardness and grain refinement (Fig. 6). Again, highcarbon alloys showed a lower hardness than low carbonalloys (Table 1). Growth inhibition was more pro-nounced with increasing amounts of inhibitor carbide,but reached a saturation limit, above which neither ahigher hardness nor a finer microstructure was obtained(Fig. 7).

4.2.3. TaC-doped alloysSmall additions (0.2 wt% TaC) did not significantly

alter the grain growth as compared with the undopedalloy, but at 1 wt% TaC a considerable growth inhibi-tion took place. The hardness of this alloy was about thesame as that of the 1 wt% Cr3C2 addition (HV30: 1615[Ta] and 1580 [Cr], respectively). At 1 wt% TaC addi-tion, nest-like precipitation of (W, Ta)C occurred inthe microstructure, independently of the gross carboncontent.

4.2.4. TiC-doped alloysFor TiC a clear growth inhibition was observed, even

at a level of 0.2 wt% TiC (Fig. 6). This inhibition wasmore pronounced in the low carbon (g-phase contain-ing) alloy. This indicates a strong additional effect, dueto the tungsten-rich melt formed in such alloys.

Even in the case of the 0.2 wt% TiC additions, pre-cipitation of (Ti, W)C occurred on cooling, indicating alow solubility of titanium carbide in nickel.

The most striking microstructural feature in TiC-doped alloys is the occurrence of plate-like WC grains(sizes up to 6 lm), which are embedded in a still fine-grained WC matrix (Fig. 8).

4.2.5. ZrC-doped alloysCompared with TiC, ZrC is an even weaker growth

inhibitor, and only works in the low carbon activityrange (i.e. in a tungsten-rich, but carbon-poor environ-ment of the growing WC). No growth inhibition at allwas observed in high carbon alloys with graphite pre-cipitations.

Precipitation of (Zr, W)C occurred even at 0.2 wt%ZrC additions, indicating a low solubility of ZrC innickel. Interestingly, such precipitates were not onlyformed in the nickel binder or at the WC/Ni interface,but also appeared to be incorporated within large WCgrains.

Fig. 3. SEM images of microstructures of WC–10 wt% Ni l.c. (left) and h.c. alloy (right); 2000�.

Fig. 4. Hardness [HV30] vs. VC-addition (wt%); WC–X wt% VC–10

wt% Ni alloys; sintered at 1480 �C for 1 h.


4.3. WC grain growth in WC–10 wt% Fe alloys

Also, for comparison purposes, two WC–10 wt% Fealloys were investigated for their grain growth behav-iour; one alloy without inhibitor additive, the other with1 wt% VC. The WC powder used for this investigationwas the same as that used as the standard grade for theWC–Ni hardmetals.

The undoped alloys showed a very fine and uniformmicrostructure, even in case of the high carbon grade(Fig. 9). Overall grain growth was more pronounced inthis variant compared with the low carbon alloy, but inboth cases the microstructure was fine and very uniform,showing only a few WC grains larger than 1 lm.

Adding VC to the WC–10 wt% Fe alloy did lead to anadditional further growth inhibition but the effect wasmuch less pronounced than in case of nickel- or cobalt-bonded grades, due to the already very strong inhibitionthrough the iron matrix (Fig. 10). The lower hardness ofthis alloy (compare Figs. 9 and 10) can be explained bythe high degree of residual porosity that occurred in thismaterial.

5. Discussion

5.1. General considerations on WC grain growth andgrowth inhibition

WC grain growth during liquid phase sintering ofWC–Co alloys is phenomenologically treated as anOstwald ripening process [8–10]. Smaller grains dissolve

Fig. 5. Microstructures of VC-doped two-phase WC–Ni alloys; sintered at 1480 �C for 1 h; magnification: 4000�; at 2.0% VC additions (V,W)C is

formed on cooling.

Fig. 6. Two-phase WC–10 wt% Ni alloys with additions of VC, Cr3C2

and TiC; sintered at 1480 �C for 1 h.


due to their higher dissolution potential (increasedchemical potential), while coarser ones grow by materialre-precipitation, thereby reducing the interface area ofthe system.

Overall (continuous) WC grain growth proceeds ra-ther slowly in conventional WC–Co hardmetals com-pared with other carbide/binder systems (VC/Co, NbC/Co, TaC/Co). This is attributed to the very low WC/Cointerface energy (< 10�2 J=m2) and the relatively highactivation energy of the solution-reprecipitation step,indicating an interface-controlled growth mechanism[11].

The growth rate of the WC in WC–Co hardmetals isremarkably increased in high carbon alloys (stoichio-metric and over-stoichiometric alloys) compared withlow carbon alloys (sub-stoichiometric alloys), and canbe significantly decreased by additions of growth in-hibitors such as VC, Cr3C2, TaC and NbC. In all cases,the influence of the ‘‘additive’’ (C, W, inhibitor) hasbeen explained by effects at the WC/Co interface. Thus,theories on the mechanism of grain growth inhibitionassume either an alteration of the interface energies oran interference of the growth inhibitor with the inter-facial dissolution–nucleation–reprecipitation steps [11].The additives are soluble in the cobalt binder and most

Fig. 7. Microstructures of two-phase WC–10wt% Ni alloys containing 1 and 2 wt% Cr3C2, respectively; magnification: 4000�.

Fig. 9. WC–10 wt% Fe alloys: two phase (left), with graphite precipitates (right); magnification: 10000�.

Fig. 8. Microstructure of a WC–1 wt% TiC–10 wt% Ni alloy; sintered

at 1480 �C for 1 h; note the plate morphology of the WC; dot-like

precipitations of (W, Ti)C form on cooling; magnification: 4000�.


apparently segregate at the WC/Co interface duringsintering.

Several mechanisms have been suggested: face-spe-cific adsorption (leading to a decrease of the respectiveinterface energies), face-oriented deposition (interfacealloying) or blocking of active growth centres of thecrystals [10], including a change in edge energy (onconsidering a two-dimensional nucleation-controlledcoarsening process) [12]. Also the retardation of graingrowth during sintering in the presence of Cr3C2-addi-tions by a reduction of the tungsten flux through thebinder phase was discussed [13].

The results obtained in this study, which extend theknowledge on WC grain growth as described above, tonickel- and iron-based hardmetals, have revealed severalnew and interesting aspects in WC grain growth andgrowth inhibition.

• First of all, the strong growth inhibition in WC–Fealloys, which occurred even without additions ofgrowth inhibitors.

• The small influence of variations in the gross carboncontent on the WC grain growth in WC–Fe alloys.

• The absence of any discontinuous WC grain growthin WC–Fe alloys (despite the small average particlesize of the starting WC: �0:35 lm).

• The strong growth in WC–Ni alloys, in particular ininhibitor free high carbon alloys.

• The significant growth inhibition in low carbon WC–Ni alloys (tungsten-rich binder environment), in par-ticular in alloys with g-formation.

• The outstanding role of VC as growth inhibitor inWC–Ni alloys, similar to that observed in WC–Cogrades [3].

• Effects of TiC on WC shapes in WC–Ni hardmetal.

The results further demonstrate that observations madeon WC–Co alloys in terms of grain growth inhibitionthrough inhibitor carbides (VC, Cr3C2, TaC, TiC, ZrC)can be directly transferred to WC–Ni alloys. For acertain inhibitor additive (e.g. VC) the finest micro-structure is obtained when the saturation concentrationof the respective compound in nickel is reached at sin-tering temperature [3]. This relationship is demonstratedin Fig. 6 for the WC–10 wt% Ni alloys with additions ofVC, Cr3C2 and TiC. Above this limit, no further growthinhibition took place.

5.2. The importance of the growth environment

The chemistry of the solid and liquid binder sur-rounding the growing WC seems to be a crucial aspect inWC grain growth. This chemistry varies significantlywith changes in the gross carbon content or additions ofgrowth inhibitors, and determines the interface chemis-try and kinetics. This is shown in Fig. 11 for the case of ahigh and low carbon WC–Ni alloy at a temperature of1500 �C.

Thus, a carbon-rich, tungsten-poor nickel inter-face (formed on sintering), significantly promotes WCgrain growth, whereas a tungsten-rich, carbon-poornickel interface has a growth inhibiting effect. Thissignificant change in binder chemistry becomes evenmore obvious if the atomic C:W ratio is considered,which changes from �2:1 (high carbon) to �1:3 (lowcarbon).

Table 2 gives several examples for the large variationsin binder chemistry, depending on the nominal compo-sition of the respective alloys. Variations in chemistryare most likely to result in both changes in interface

Fig. 10. Microstructure of a WC–1 wt% VC–10wt% Fe alloy; HV30: 1884; sintered at 1350 �C for 1 h; magnification: 10000�.


energy (i.e. driving force for growth) as well as changesin activation energies and mass transport of the nucle-ation/growth process (growth kinetics; resistance againstgrowth).

Only recently it was postulated that the formation ofmetal–carbon clusters inhibits liquid phase diffusion ofW and C atoms in the Co-rich melt, and that the graincoarsening is impeded by the incorporation of W and Catoms in such a stable cluster form. The strong bondingbetween the refractory metal (W, V, Cr, Ta) and non-metal (carbon) was considered to be the key for clusterstabilization [16].

The present work demonstrates that the higher themetal-to-carbon ratio (W+V/C, W+Cr/C, W+Ta/C)

for a certain alloy (binder), the more effective is thegrowth inhibition in WC–Co(Ni,Fe) alloys (the upperlimit is set by the thermodynamics and reaches itsmaximum in low carbon alloys at temperature). In thisregard it is important to consider that although smallamounts of inhibitor carbides are commonly added(0.2–1 wt%), large amounts of inhibitor atoms are dis-solved in the binder at temperature (see Table 2).

More generally speaking, the nature of the binder(Co, Ni, Fe) contributes to determining the growth be-haviour by influencing the metal-to-carbon bond rela-tionship. For example, iron has the highest affinity tocarbon, followed by cobalt and nickel. This affinity canalso be interpreted as the ability to form stable metal–carbon bonds (also in the liquid phase), the iron mask-ing the carbon, and impeding carbon transport andprecipitation by increasing the activation energies of thenucleation and growth processes (i.e. increasing the re-sistance against growth).

A decrease in the interface energy of the WC/binderinterface might also be a possible explanation for theextremely low coarsening rate of the WC in case of theiron binder (through bond formation), compared withthe WC–Co and WC–Ni systems.

The strong influence of the respective binder systemon WC grain growth is demonstrated in Fig. 12 for thecase of three high carbon alloys (containing graphite

Fig. 11. Nickel-rich area of the Ni–W–C phase diagram at 1500 �C,according to [15].

Table 2

Melt composition of alloys based on different binders and carbon activitiesa

Alloy at.% High carbon (WþM)/Cb Low carbon (WþM)/Cc

wt% Binder

at 1500 �Cat.% Binder

at 1500 �Cwt% Binder

1500 �Cat.% Binder

1500 �C

WC–10 Fe 72% WC 19.4% W 5.7% W 0.27 48.0% W 19.6% W 1.5

28% Fe 4.7% C 21.1% C 2.1% C 13.3% C

75.9% Fe 73.2% Fe 49.9% Fe 67.1% Fe

WC–10 Co 73%WC 22.5% W 7.5% W 0.5 48.3% W 21% W 1.9

27% Co 2.9% C 15% C 1.7% C 11% C

74.6% Co 77.5% Co 50.1% Co 68% Co

WC–10 Ni 73% WC 16.3% W 5.4% W 0.54 41.5% W 17.6% W 2.9

27% Ni 2% C 10% C 0.9% C 6% C

81.7% Ni 84.6% Ni 57.6% Ni 76.4% Ni

WC–10 Ni–1

TaCc

72.2% WC 15.1% W 5.2% W 0.76 39.4% W 17.2% W 3.4

27% Ni 1.9% C 10.1% C 0.85% C 5.7% C

0.8% TaC 75.9% Ni 82.2% Ni 54.6% Ni 74.8% Ni

7.1% Ta 2.5% Ta 5.1% Ta 2.3% Ta

WC–10 Ni–1

VCb

70.9%WC 15.3% W 5% W 1.3 39.65% W 16.4% W 4.2

26.6% Ni 1.9% C 9.5% C 0.86% C 5.5% C

2.5% VC 76.6% Ni 78.2% Ni 55% Ni 71.4% Ni

6.2% V 7.3% V 4.5% V 6.7% VaValues taken from [14,15]; temperature: 1500 �C.bM� � �V, Ta.c This assumed that the addition is fully dissolved in the nickel at 1500 �C. The values are estimates, since no information is available on the

quaternary systems.


precipitations), originating from the same WC powder(Fig. 1) but with different binder matrices (Co, Ni, Fe).No inhibitor carbides were added.

6. Conclusion

The present investigation on WC grain growth inWC–Ni and WC–Fe hardmetals has revealed severalnew and important aspects which might render a moregeneral understanding of the growth process.

Three main chemical parameters were elaborated tocontrol WC grain growth under the experimental con-ditions chosen.

• The chemical nature of the binder matrix (Fe, Co,Ni), which surrounds the growing (and dissolving)WC grains.

• The carbon activity, which prevails during the sinter-ing process in the respective alloy system (and whichis determined by the alloy gross carbon content).

• As well as the presence of growth inhibitors, such as,e.g. VC or TaC.

WC grain growth occurs to the least extent in ironbinder alloys where it is also only slightly influenced bythe alloy gross carbon content. By contrast, WC growthis most pronounced in WC–Ni alloys and a strong in-fluence is exerted by the carbon potential. Cobalt alloys

Fig. 12. Microstructures of WC–10 wt% Co (Ni, Fe) alloys, based on the same WC powder (shown in Fig. 1).


are intermediate between showing a moderate overallWC grain growth and a less pronounced influence of thealloy gross carbon content compared with WC–Ni.

The strong influence of the carbon activity on overallWC grain growth can be explained by the fact that thecarbon activity significantly co-determines the bindercomposition at temperature (both of the solid and liquidbinders), and thus the interface chemistry of the sus-pended WC, which determines the rate of crystalgrowth. High carbon alloys exhibit a carbon-rich buttungsten-poor binder, which obviously enhances theWC grain growth; whereas, low carbon alloys exhibit atungsten-rich and carbon-poor binder, which acts as agrowth inhibiting environment compared with the for-mer.

The strong influence of the iron-binder metal itself(Fe, Co, Ni) on WC grain growth can be explained as aresult of changes in the interface energy of the respectiveWC/binder interface (i.e. a change in the driving force)as well as in interactions between the binder atoms withthe ‘‘growth active’’ carbon atoms (i.e. an increase inactivation energy of the interface reaction). The latterhypothesis assumes the formation of stable metal/car-bon clusters through bond formation which results in adepletion of ‘‘free available’’ carbon atoms necessary forthe further growth of the WC crystals. This strong im-pact of the binder chemistry on WC grain growth sup-ports the concept of an interface- controlled growthmechanism, as assessed earlier from WC growth studiesin the WC–Co system.

Acknowledgements

The present work was supported financially withinthe framework of a group project ‘‘Concepts for NewMicrostructural Design of Hardmetals by using Ad-vanced Powders and Processing Techniques’’ in which

the following companies participated: H.C. Starck,Kennametal, Mitsubishi Materials Inc., SumitomoElectric Ind., Teledyne Metalworking Products, UnitedHardmetal and Wolfram Bergbau-und H€uuttenges.

References

[1] Prakash L. In: Bildstein H, Eck R, editors. Proceedings of the

13th International Plansee Seminar, Reutte, Austria, vol. 2. 1993.

p. 80–109.

[2] US Patent 6,024,776: Cermets having a binder with improved

plasticity; 2000 Feb 15.

[3] Hayashi K, Fuke Y, Suzuki H. J Jpn Soc Powders Powder Metall

1972;19:67–71.

[4] Suzuki H, Yamamoto T. J Jpn Soc Powders Powder Metall

1968;15:68–71.

[5] Human AM, Northtrop IT, Luyckx SB, James MN. J Hard Mater

1991;2:245–56.

[6] Ekemar S, Lindholm L, Hartzell T. In: Ortner HM, editor.

Proceedings of the 10th International Plansee Seminar, Reutte,

Austria, vol. 1. 1981. p. 477–92.

[7] Holleck H, Kleykamp H. Int J Ref Metals Hard Mater

1982;1:112–6.

[8] Wagner C. Z Elektrochem 1961;65:581.

[9] Fischmeister H, Grimval G. In: Kuczynski GC, editor. Sintering

and Related Phenomena. New York: Plenum Press; 1980. p.

119–49.

[10] Schubert WD, Bock A, Lux B. Int J Ref Metals Hard Mater

1995;13:281–96.

[11] Exner HE, Fischmeister H. Arch fd Eisenh€uuttenwesen

1966;37(2):417–26.

[12] Choi K, Hwang NM, Kim D-Y. Powder Metall 2000;43(2):

168.

[13] Okada K, Taniuchi T, Tanase T. Effect of Cr3C2 addition on the

sintering of cemented carbide. In: International Conference on

Powder Metallurgy and Particulate Materials, Las Vegas. 1998.

[14] Gustafson P. Metall Trans A 1987;18:175–88.

[15] Gabriel A, Pastor H, Deo DM, Basu S, Allibert CH. In: Bildstein

H, Ortner HM, editors. Proceedings of the 11th International

Plansee Seminar, Reutte, Austria, vol. 2. 1985. p. 509–25.

[16] Sadangi RK, McCandlish LE, Kear BH, Seegopaul P. Int J

Powder Metall 1999;35:27–33.


wc grain growth and grain growth inhibition in nickel and iron binder hardmetals

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