Cermets As Potential Materials for High-Temperature Service

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REPORT 99

CL. o Q_ ADVISORY GROUP FOR AERONAUTICAL RESEARCH AND DEVELOPMENT

REPORT 99

CERMETS AS POTENTIAL MATERIALS FOR HIGH-TEMPERATURE SERVICE

O. A. SANDVEN

APRIL 1957

NORTH ATLANTIC TREATY ORGANIZATION PALAIS DE CHAILLOT. PARIS 16

REPORT 99

NORTH ATLANTIC TREATY ORGANIZATION

ADVISORY GROUP FOR AERONAUTICAL RESEARCH AND DEVELOPMENT

CERMETS AS POTENTIAL MATERIALS FOR HIGH-TEMPERATURE SERVICE

0. A. Sandven

This Report was presented at the Fifth Meeting of the Structures and Materials Panel, held from 24th to 27th April 1957, in Oslo, Norway SUMMARY

A review is given of the chemical, physical and mechanical properties of the most important and promising Hard Metals and Cermet systems, with special attention to the creep resistance and ductility.

Some experimental results on the system NbC-TiC Ni are reported.

SOMMAIRE

Revue des proprietes chlmiques, physiques et mecaniques des metaux durs et de» cermets les plus importants et les plus prometteurs, en considerant plus particullerement leur resistance au fluage et leur ductilite. Presentation de quelques resultats d'essais obtenus avec le systeme NbC-TiC Ni.

666,762

2a9g2:3e3c5c

ii CONTENTS

page

SUMMARY i i

LIST OF TABLES iv

LIST OF FIGURES iv

1. INTRODUCTION 1

2. HARD METALS AND THEIR PROPERTIES 1 2.1 General 1 2.2 Carbides 2 2.3 Borides, Nitrides and Silicides 2

3. METAL BONDED HARD METALS (CERMETS) 3 3.1 Gene ra1 3 3.2 Strength at Elevated Temperatures 3 3.3 Impact Strength and Thermal Shock Resistance 4

3.4 Oxidation Resistance 4

4. CONCLUSIONS 5

REFERENCES 6

TABLES 7

FIGURES 9

DISTRIBUTION

iii LIST OF TABLES

page

TABLE I - Properties of Carbides 7

TABLE II - Properties of Nitrides 7

TABLE III - Properties of Borides 8

TABLE IV - Properties of Sillcides 8

LIST OF FIGURES

Fig. 1 Mutual solid-solubility in binary carbide systems 9

Pig. 2 Mutual solid-solubility in binary nitride systems 10

Fig. 3 Mutual solid-solubility in binary nitride-carbide systems 11

Pig. 4 Mutual solid-solubility in binary disilicide systems 12

Fig. 5 Isothermic sections of ternary disilicide systems. 1300°C 13

Fig. 6 100 hr strength of TiC cermets 15

Pig. 7 100 hr strength of TiC-base cermets 16

Fig. 8 Stress-rupture time (1% strain). TiC-base cermets at 950°C 17

Fig. 9 Stress-rupture time. 980°C 18

Fig.10 Oxidation of WZ-cermets. 1100°C 19

Pig.11 Oxidation of cermet and superalloy 20

Pig.12 Oxidation of TlC-Cr3C2. 1 hr 21

Fig.13 Oxidation of WZ-cermets 22

Fig.14 Oxidation of TiC-base cermets. 1100°C 23

Fig.15 Oxidation of 70 (TiNb)C, 24 Ni, 6 Cr cermets 24

iv CERMETS AS POTENTIAL MATERIALS FOR HIGH-TEMPERATURE SERVICE

0. A. Sandven*

1 . INTRODUCTION

Technical development, especially on the field of jet propulsion, has undoubtedly been delayed by the lack of suitable heat-resistant construction materials. The alloys at present available for such purposes, that is Ni-base and Co-base alloys, lose their strength so rapidly with increasing temperature that they cannot be used with any success above 800 - 900°C. and the development of other and more suitable alloys for high-temperature purposes, is therefore a problem of primary importance In modern metallurgy.

Considerable research work has been carried out recently to solve this problem and, among the various types of materials which seem to be of potential use, the cemented Hard Metals, or cermets, play an important part.

Many reports dealing with cermets, specially TiC-base cermets, have been published, and it has been shown that it is possible to obtain cermet materials with supreme high-temperature strength and oxidation resistance. Unfortunately, however, all the cermet materials known so far also have undesirable properties, which makes them unfit for constructional use, except for some special and very limited purposes. Among these undesired properties, the lack of impact strength is possibly the most difficult and serious to overcome, although high cost, difficult production and machinability also have to be considered.

2. HARD METALS AND THEIR PROPERTIES

2.1 General

The metallic hard metals, that is, the carbides, borides, nitrides and sllicldes of the transition metals in the (d) - (f) group, have some common properties. The most important of these are:-

(a) Very high melting point

(b) Very high hardness

(d) Metallic character (metallic lustre, conductors of heat and electricity)

(e) They have mostly a interstitial-solid-solution structure

(f) They have a very high modulus of elasticity.

Many of the (d) - (f) group metals form more than one chemical compound with each

of the non-metals C. N, B and Si (ex WC and W2C), but it is mostly the mono-carbides and -nitrides, diborides and disillcides which have been studied.

*Sivilingenior, Research Metallurgist, Norwegian Defence Research Establishment 2.2 Carbides

The carbides are the best known hard metals. With the exception of WC, all the metallic monocarbldes have an P.P.C, - structure. They have melting points above 2000°C, high modulus of elasticity, good oxidation resistance and little or no ductility. Table I gives some properties of the most important metallic carbides, and also of the two carbides B2C and SIC.

From the present point of view, the carbides TiC, TaC, NbC and Cr3C2 are of primary importance. The first three are completely soluble in each other in the solid state, and work on the quasi-binary systems TiC-TaC, TiC-NbC and NbC-TaC have been published (see Reference 2. pp. 165-196). Unfortunately, however, in cermet development, most work deals with Ta(Nb)C in TiC (Ref.3). This gives some information of the Influence of the pure carbides NbC and TaC on TiC, since NbC and TaC seem to be very similar, but the exact nature of this influence cannot be found in this way. Workers using the pure carbides4 have found that NbC-addition to TiC-cermets increases the creep resistance more than a similar TaC-addition. Also the oxidation resistance of TiC will be increased considerably by the addition of TaC, NbC and Cr3C2 (Ref. 2, pp. 659-667 and Ref.5). It is of interest to notice that the carbides TaC and NbC have some ductility1. This does not mean that they can be deformed plastically to any great degree, but merely that they can undergo some plastic deformation without failure.

As might be expected, the mutual solid-solubility is very great in quasi-binary carbide-carbide systems (see Figure 1 and Reference 2, pp. 59-157, 326). All the cubic carbides are completely soluble in each other in the solid state, with the exception of the pair VC-ZrC. This system has very narrow fields of terminal solid- solutions, possibly due to the rather large difference between the lattice para meters of VC and ZrC. Some of the carbides, or carbide-systems, will possibly not be of any potential value for the development of high-temperature materials. This is so with HfC, which is not available in any great quantity. The high densities of TaC and WC will possibly restrict their use, save for rather small additions to other carbides, and the extremely hard and brittle non-metallic carbides B14C and SIC may possibly also be of little value. However, the remaining carbides, in some combination with each other, or in a pure form, may be able to form the basic constituents in materials suitable for high-temperature use; although, in spite of considerable research which has been undertaken on these hard metals, their nature and properties are not yet well understood.

2.3 Borides, Nitrides and Silicides

The properties of the metallic borides, nitrides and silicides (d) - (f) group transition metal) are not quite so well known as the properties of the carbides, but they are in many respects very similar to the carbides. Again the common properties are high hardness, high melting point and great chemical stability, although the crystal structures are somewhat more complex.

The mutual solid-solubility of nitride-nitride systems (Ref. 2, pp. 212-250) are shown in Figure 2. Perfect solid-solubility is found between cubic nitrides, except in systems VN-ZrN and VN-HfN. The hexagonal structure of TaN, restrict the solid- solution formation in systems between this component and one of the cubic nitrides. Figure 3 gives the solubility on some nitride-carbide systems (Ref. 2, pp. 212- 250). Because of similarity in structure, many of these systems have complete solid- solution formation, but ZrC, is not stable in the presence of N at very high temperatures.

Relatively little is known about the boride-boride systems (Ref. 2, pp. 259-292) but, by analogy with the carbides and nitrides, it is to be expected that a large mutual solid-solubility between the diborides of Ti, Zr, Hf and V, Mb and Ta will exist, because they all have the same structure (ACB2-type hexagonal).

In boride-carbide systems, no solid-solubility formation can be expected, because B cannot substitute C in the metal lattice. The diborides are mostly stable In the presence of carbon (Ref.2, pp. 259-292) but the diborides of V, Nb and Ta decompose during melting (in the presence of carbon) to Monoborides + Bor.

It is interesting to note that the _d is 1lie ides TaSi2, MoSi2 and NbSi2 have some ductility. TaSi2 (which is the most ductile one) and MoSi2 have also excellent oxidation resistance.

The mutual solid-solubility in disilicide systems is fairly well known (Ref. 2, pp. 301-325 and Refs. 6,7) (Fig.4). The variation in crystal structure among the sili cides naturally restricts the solid-solution formation, but the hexagonal slllcldes TaSi2, NbSi2 and VS12 are completely soluble in each other in the solid state. The systems TiSi2 - MoSi , and TiSi - WSi have intermediate solid-solutions, but no terminal solid-solutions, due to the difference In crystal structure.

Even some ternary silicide systems have been investigated6 (Pig.5).

3. METAL BONDED HARD METALS (CERMETS)

3.1 General

Alloys of cemented hard metal, preferably carbides, have been used for many years as tool-bits, but the use of this type of material for constructional purposes is relatively new, and a great amount of research and development work has been done to obtain really useful cermet materials.

3.2 Strength at Elevated Temperatures The TiC-cermets have a very high strength at elevated temperatures, and will usually be superior in this respect to the ordinary high-temperature materials (superalloys).

The nature and amount of binder metals, have a pronounced effect on the creep resistance of pure TiC-cermets. With 20% binder metal, Co is superior to Ni (Fig.6), but still better properties can be obtained if the pure Ni- or Co-binder is substituted with a Co- or Ni- Co- Cr- alloy".

The creep resistance will generally decrease (but not necessarily proportionately) with increasing amount of binder and an optimum fracture strength can often be obtained with a certain amount of binder. A 80 TiC - 20 (Co, Cr, Mo, Nb, V) is reported to have a maximum of 100 hr strength with 40% binder at 750°C, and with 30% at 850° and 950°C. Addition of other carbides to the TiC-phase can also have a very strong effect on the high-temperature strength of the material. The effect of TiC-additlons on the strength of a TiC-base cermet are shown1* in Figure 7, and the effect of some other carbide addition4 in Figure 8.

Some alloys which are commercially available have been developed on the base of mixed carbides. The strength of one of these alloys, Kentanium K 138 A, which is composed of 65% TiC. 15% (NbTaTi)C and 20% Co (Pig.9) is shown in relation to some ordinary superalloys, the cast stellite Vitallium, and the wrought Co-base alloy S-816 (Ref.3). (This last mentioned alloy is used in the turbine buckets in J-35 engines). Even better relative performance of the K 138 A-alloy will be evident if the densities of the alloys are considered. The S-816 alloy has a density nearly 50% greater than the K 138 A, and this is a fact of great importance, because the main stresses in a gas-turbine bucket are the centrifugal stresses set up by the rapid revolution of the turbine, and these stresses are proportional to the density of the material.

In recent years, other hard metal cermets have also been developed, especially on boride- and sillcide-bases. However, relatively little information on the high- temperature strength of these materials has so far been published, though the excellent properties of the pure disillcides makes it very probable that superior high-temperature materials can be developed on the base of these hard metals.

3.3 Impact Strength and Thermal Shock Resistance

The very low impact strength of cermet materials seriously restricts their use for constructional purposes. An increase in impact strength can be obtained by increasing the amount of binder metal but, to obtain a reasonable ductility, the amount of binder metal has to be so high that the creep resistance will be seriously decreased. The Cermet WZ 12 C (50 TiC, 50 Nl-Co-Cr) (Ref.8) has an impact strength of 0.64 kg/cm2 (unnotched specimens), which must be considered relatively high for the present state of cermet development, but it will be necessary to increase this value considerably to obtain a useful turbine-bucket material. Not only the chemical composition, but probably also grain size, homogeneity, impurity contents and so on will affect the impact strength, and much remains to be done in this field, as the influence of such factors upon the impact strength of cermets is little known.

The thermal shock resistance of cermet materials is relatively good, and should generally be comparable with ordinary heat-resistant alloys4, although the low ductility is a great disadvantage. The best method of measuring the thermal shock resistance of materials for turbine applications is to test-run turbine-buckets in an actual turbine, and experiments of this kind show promising results.

3.4 Oxidation Resistance

The oxidation resistance of the hard metals and cermets is generally very good. It is, however, necessary to secure a minimum oxidation rate at very high temperatures if the materials are to be useful in practice, for high-temperature applications. The oxidation resistance of the binder metal phase, as well as of the hard metal phase, has to be considered. Some commercial cermets, as the WZ-alloys, have been tested on oxidation resistance with variation in the binder phase (Ref.2. pp. 659-667) (Fig.10), and the relative resistance of a similar alloy, Elmet H.R, as compared with a conventional heat- resistant alloy, Nimonic 80a, has been determined in a mixture of air and kerosine (Ref, 2. pp. 659-667) (Pig. 11).

Microscopical examinations of oxidised TiC-Ni-Cr specimens, shows a preferred oxidation of the carbide phase5 and, to increase the oxidation resistance of the carbide phase, additions of other metal-carbides are profitable. The influence of Cr on TIC is shown in Figure 12 (Ref. 2, pp. 659-667).

9 Assuming the theory of Wagner to be valid on the reaction TiC - Ti02, the diffusion of oxygen through the T102-layer will determine the rate of oxidation. The diffusion rate will be determined by the number of vacant anione sites in the oxide layer.

Putting Ci/C2 = constant, where Cj = the equilibrium concentration of vacant anione sites and C2 - the equilibrium concentration of quasi-free electrons,

Cx will decrease if C2 is increased, and consequently the rate of oxidation will decrease. An increase in the concentration of quasi-free electrons can be obtained by additions of carbides of metals with higher valency than Ti. Additions of carbides of the penta-valent metal Nb and Ta should therefore increase the oxidation resistance of TiC and Tie-cermets. This is clearly shown in Figure 13 (Ref. 2, pp. 659-667) which represents the oxidation rates of the cermets WZ 1 b and WZ 3. The first alloy has the composition 60 TIC, 32 Ni, 8 Cr, but in WZ 3, one-sixth of the TiC Is replaced by Ta(Nb)C.

At N,D.R.E.5 a systematic Investigation of the oxidation resistance of Tl(Nb)C-Ni-Cr cermets has been carried out and a remarkable decrease of the oxida tion rate by the addition of Nb has been found (Fig.14). (These tests were made on ordinary cold-pressed, hot sintered specimens in an ordinary atmosphere, by the use of a thermo-balance furnace). The effect of increasing Nb-addition on the oxidation rate is shown in Figure 15 for three different temperatures5.

4. CONCLUSIONS The high-temperature strength of cermet materials is generally superior to the conventional high-temperature constructional materials. Their oxidation resistance can also be increased to a very high level, but their lack of ductility makes them unfit for constructional use. Relatively few cermet systems have been properly investigated, and it may be possible to overcome the lack of impact strength by using new Hard Metal-Binder Metal combinations, or by better production methods. If it is possible to Increase the inpact strength to a moderate value without the loss of creep resistance and oxidation resistance, the cermets will make excellent materials for high-temperature purposes. REFERENCES

1. Campbell, I.E. The Vapour-Phase Deposition of Refractory Materials. Powel, C.P. Journal of the Electrochemical Society, Vol. 96, et al. 1949, pp. 318-333.

2. Kieffer, R. Hartstoffe und Hartmetalle. Springer-Verlag Wien, Schwartzkopf, P. 1953.

3. Remond, J.C. Cemented Titanium Carbide. Transactions of the Smith, E.N. American Institute of Mining and Metallurgical Engineers, Vol. 185, 1949, pp. 987-993.

4. Harris, G.T. The Creep Strength of TiC-base Materials. The Iron Child. H.C. and Steel Institute. Symposium of Powder Metallurgy, et al. 1954. pp. 287-291.

5. Nordheim, R. Unpublished reports at the Norwegian Defence Research Bardstatt, R. Establishment, 1954-1956. et al.

6. Nowotny, H. Uber den Aufbau von Siliziden. 2. Plansee Seminar, Kudlelka, E. 1955. Springer-Verlag Wien. 1956. pp. 166-172. et al.

7. Kieffer, R. Silicides of Transition Metals. The Iron and Steel Benesovsky, P. Institute, Symposium of Powder Metallurgy, 1954. pp. 292-301.

8, Kolb, P. 2nd Plansee Seminar. 1955, Springer-Verlag Wien, 1956, p. 126.

9. Hauffe, K. The Mechanism of Oxidation of Metals and Alloys. Progress in Metal Physics, Vol.4, Pergamon Press, London 1953. pp. 71-104. TABLE I

Properties of Carbides'

Hard Heat Me 11ing Modulus of Oxidation Struc Dens i ty ness Condition Ducti Carbide Point Elasticity Res istance ture (g/cm3) (kg/ (cal.l lity (kg/cm2) cm2) (C°) cm.s.C0) (°C)

HfC F.F.C. 12.7 - 3890 - - 0 1100-1400 TaC P.P.C. 14.5 1800 3880 0.053 29,100 1 1100-1400 ZrC F.F.C. 6.9 2600 3530 0.049 - 0 1100-1400 NbC P.F.C. 7.8 2400 3500 0.034 34.500 1 1100-1400 TiC P.P.C. 4.9 3200 3140 0.041 32.200 0 1100-1400 WC S. Hex. 15.7 2400 2870 - 72,200 0 500-800 VC P.P.C. 5.4 2800 2830 - 27.600 0 800-1100

Mo2C C.P. Hex 9.2 1500 2690 - 22.100 0 500-800 Cr 3c2 Rhomb. 6.7 1300 1895 - - 0 1100-1400

BUC 2.5 3700 2450 - 29,600 0 1100-1400 SiC 3,2 3500 2200 0.037 - 0 1400-1700

0 denotes no ductility See Reference 1, pp. 318-333 1 denotes little ductility and Reference 2, pp.59-157, 326

TABLE II

Properties of Nitrides*

Me Iting Oxidation Dens i ty Hardness Nitride Structure Point Duetility Res istance (g/cm*) Cfeg/cn.2,) (C°) (°C)

TaN C.P, Hex. 14.1 1400 3090 0 500-800 ZrN P.P.C. 6.9 1400 2980 0 1100-1400 TiN P.F.C. 5.2 1400 2950 0 1100-1400 NbN P.P.C. 8.4 1400 2050 0 500-800 VN P.P.C. 6.0 2800 2050 0 500-800 BN - 2.2 - 2730 0 1100-1400

• See Reference 1 and Reference 2, pp. 212-250 TABLE III

Properties of Borides*

Heat Me 11ing Ox ida t ion Density Hardness Boride Structure Condit ion Point Duetility Resistance (g/cm3) (kg/mm2) (cal.cm.s.C0) (C°) (°C)

HfB2 - 11.2 - - 3060 0 1100-1700

ZrB2 Hex. 6.2 2200 0,055 2990 0 1100-1700

T1B2 Hex. 4.4 3400 0.063 2900 0 1100-1700

TaB2 Hex. 11.7 1400 0.026 2900 0 1100-1400

NbB2 Hex. 6.6 1400 0.040 2900 0 1100-1400

V2B Tetr. 16.6 - - 2770 0 800-1400

MoB2 Hex. 8.0 1380 - 2250 0 1100-1400

VB2 Hex. 5.1 1400 - 2100 0 800-1400 Cr B Ort. Rhomb. 6.0 2100 - 1550 0 1400-1700

• See Reference 2, pp. 59-157, 326. and pp. 259-292.

TABLE IV

Properties of Silicides*

Melting Oxidation Density Hardness Si lieide Structure Point Duetility Resistance (g/cm3) (kg/mm2) (C°) (°C)

TaSi2 Hex. 8.8 1560 2400 1 - 2 1100-1400

W Si2 Tetr. 9.3 1090 2150 0 1100-1700

MoSl2 Tetr. 6.1 1290 2030 1 >1700

NbSi2 Hex. 5.3 1050 1950 1 800-1100

ZrSi2 Ort.Rhom 4.9 1030 1700 0 800-1100

CrSi2 Hex. 4.4 1150 1570 0 1400-1700

TiSl2 Ort.Rhom 4.4 870 1540 0 800-1100

• See Reference 2. pp. 59-157. 326. 301-325. VC NbC TaC ZrC HfC Cr3C2 Mof JVC

1900' 2000* TiC m m m • % o €> €) 50 20 ffO 0 1600' 2000* VC • • O % 0 € € 50 0 55 0 2100* 2000* NbC • • m C € o ~tT0 0 30 0 1500' 2000* TaC 9 • m € 0 <0 » J5 0 KOC" M0v7* ZrC % €) o o a?0 0 20 0 HfC € O €)

CrC ? ? 3 2 Mof 0

SOLVENT 1 Partial Solid-Solubility. Complete Solid-Solubility. Figures in Mot- % (Solute) SOLVEN-OT VENT ^_F Complete Solid-Solubility SOLVENT to be expected. Data Partial Solid-Solubility not available. to be expected. Data SOLVENT not available. o No Solid-Solubility. Pig.1 Mutual solid-solubility in binary carbide systems 10

VN NbN TaN ZrN HfN

TIN • m o m % VN m G o o 7 5

NbN Q • # TaN o €

ZrN #

SOLVENT

Complete Solid-S o I utility 1 Partial Solid Solubility H3 Figures in MolV, (Solute) .VENT \__J Complete Solid-Solubility to be expected. Data not available. SOLVENT

No Solid-Solubility. Partial Solid-Solubility to o VENT \_y be expected. Data nof available.

Fig.2 Mutual solid-solubility in binary nitride systems 11

TiC ZrC HfC VC NbC TaC

ZrN O O

HfN

NbN

TaN <3 O (3 3

No Sotid-Solubility to be Complete Solid-Solubility expected. Data not available

Complete Solid-Solubility Partial Solid-Solubility to be expected. Data not available O on Carbide-Side.

Partial Solid-Solubility on No Solid-Solubility Carbide-Side to be expec o ted. Data not available

Pig.3 Mutual solid-solubility in binary nitride-carbide systems 12

VSi2 NbSi2 TaSi2 ZrSi2 Mos;2 WSi2 GrSl2

TiSi 2 m m 3 3 # m €0-97 2 W 0 50 3 55 40— 92 5 90 9 VSI2 • • o € • O

9 9 NbSi2 • o • 0

To Si2 9 o • o © 25 25 <0 //

— 9 ZrSi2 o • o 5 0

MoS) 2 • «» JO

WSi2 €)

So/vent

Port/O/ Solid-Solubility. Complete Solid-Solubility So/vent -o" Figures in Mot */. (Solute) Partial Solid-Solubility to Complete Solid-Solubility lo be be expected. Data not expected. Data not available available.

Intermediate Solid-Solu o No Solid-Solubility. I bitt'ty. Figures in Mot %.

Pig.4 Mutual solid-solubility in binary disilicide systems 13

CrSi2 Mo Si 2 WSir C40 mo TjiJ cit

TiSi2 TiSi2

Cr Si2 Mo Si2 ZrS'12 Mo Si2

C40 cit C49 7F]

Pig.5(a) Isothermic sections of ternary disilicide systems. 1300°C 14

ns '2 TVS/.

TaSi WSi2 Cr Si2 TaSI2 C40 urn C40 C40 |

TiSi2 Mo Si'2

ToSi2 Mo Si2 CrSi2 Ta Si2 C40 C40 E3

Fig.5(b) Isotherraic sections of ternary disilicide systems. 1300°C 30-

-4 80 TiC, 20 Co, CrMo, Nb, V-alloy

« 80 TiC,20Ni,Co,Cr,W,Mo,Ta-alloy

-*» 80 TiC. 20 Co.

-O 80 TiC, 20 Ni. 20

IS) 10- »UJ i~ 10

I 750 850 950 TEMP C°-

Fig. 6 100 hr strength of TiC cermets 16

[ 00 Ti(Ta)C-20 Co.Cr,Mo,Nb,V-aUoy~]

IE to V) Uj 5 U)

% TaC

Pig.7 100 hr strength of TiC-base cermets 17

ADDITION OF 10*/. OF INDICATED CARBIDES TOA 80TiC-20Ni CERMET

MoC

10 ibT 1000 HOURS

Fig.8 Stress-rupture time (1% strain). TiC-base cermets at 950 C 1000 HOURS

Pig.9 Stress-rupture time. 980°C tfi 1

I 0.5 A

Pig.10 Oxidation of WZ-cermets. 1100°C 20

0.6

0.7

0.6

0.5

S ELME r H.R. 0.3

Uj 10 NIMOI HC 80A 2 OJ

50 MRS 0.1

600 900 1000 1100 1200 TEMP C° —

Pig.11 Oxidation of cermet and superalloy 21

at A 1,0% Cr • • 0,1 o o 0,5 -— o——o 2.1 -- - D • 3.8 —*- 5.0 —

4.0

3.5

3,0

2,5 •f t 2,0 s «•0• 2 c P >5

¥>

0.5 600 700 800 900 1000 1100 1200 1300 1400

TEMP. C

Pig.12 Oxidation of TiC-Cr3C2. 1 hr to 1.5-1 to

60 TiC, 32 Ni, 8 Cr.

50 TiC, 10 Ta(Nb)C, 32 Ni, 8 Cr.

1.0 mt

V) i 55 0.5

V t HRS

Fig.13 Oxidation of WZ-cermets 70 TiC, 30 N,

70 TiC . 30 Co

70 TiC . 12 Ni, 12 Co. 6Cr

70 TiC, 24 Co, 6Cr

70 (Ti. Nb)C , 30 Ni

VT~ hrs

Fig.14 Oxidation of TiC-base cermets. 1100°C U 24

6.25 12.50 18.75 25.0 30.0 ATOM % Nb fig. 15. IN CARBIDE Fig.15 Oxidation of 70 (TiNb)C, 24 Ni, 6 Cr cermets DISTRIBUTION

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AGARD Report 99 666.762 AGARD Report 99 666. 762 North Atlantic Treaty Organisation, Advisory Group North Atlantic Treaty Organisation, Advisory Group for Aeronautical Research and Development 2a9g2:3e3c5c for Aeronautical Research and Development 2a9g2:3e3c5c CERMETS ASPOTENTIAL MATERIAL FOR HIGH-TEMPERATURE CERMETS ASPOTENTIAL MATERIALS FOR HIGH-TEMPERATURE SERVICE SERVICE O.A. Sandven. O.A. Sandven. 1957. 1957. 24 pages, incl. 15 Pigs., 9 Refs. 24 pages, incl. 15 Figs., 9 Refs.

A review is given of the chemical, physical and A review is given of the chemical, physical and mechanical properties of the most important and mechanical properties of the roost important and promising Hard Metals and Cermet systems, with promising Hard Metals and Cermet systems, with special attention to the creep resistance and special attention to the creep resistance and ductility. ductility.

Some experimental results on the system NbC-TIC Ni Some experimental results on the system NbC-TIC Nl are reported. are reported.

Presented at the Fifth Meeting of the Structures Presented at the Fifth Meeting of the Structures and Materials Panel, held from 24th to 27th April and Materials Panel, held from 24th to 27th April 1957, in Oslo, Norway 1957, in Oslo, Norway

AGARD Report 99 666.762 AGARD Report 99 666.762 North Atlantic Treaty Organisation, Advisory Group North Atlantic Treaty Organisation, Advisory Group for Aeronautical Research and Development 2a9g2:3e3c5c for Aeronautical Research and Development 2a9g2:3e3c5c CERMETS AS POTENTIAL MATERIALS FOR HIGH-TEMPERATURE CERMETS ASPOTENTIAL MATERIALS FOR HIGH-TEMPERATURE SERVICE SERVICE 0. A. Sandven. 0. A. Sandven. 1957. 1957. 24 pages, incl. 15 Figs., 9 Refs. 24 pages, incl. 15 Pigs., 9 Refs.

A review is given of the chemical, physical and A review is given of the chemical, physical and mechanical properties of the most Important and mechanical properties of the most important and promising Hard Metals and Cermet systems, with promising Hard Metals and Cermet systems, with special attention to the creep resistance and special attention to the creep resistance and ductility. ductility.

Some experimental results on the system NbC-TiC Nl Some experimental results on the system NbC-TiC Nl are reported. are reported.

AGARD Report 99 666. 762 AGARD Report 99 666. 762 North Atlantic Treaty Organisation, Advisory Group North Atlantic Treaty Organisation, Advisory Group for Aeronautical Research and Development 2a9g2:3e3c5c for Aeronautical Research and Development 2a9g2: 3e3c5c CERMETS AS POTENTIAL MATERIALS FOR HIGH-TEMPERATURE CERMETS AS POTENTIAL MATERIALS FOR HIGH-TEMPERATURE SERVICE SERVICE O.A. Sandven. O.A. Sandven. 1957. 1967. 24 pages, Incl. 15 Figs., 9 Refs. 24 pages, Incl. 15 Figs., 9 Refs.

Some experimental results on the system NbC-TiC Ni Some experimental results on, the system NbC-TIC Ni are reported. are reported.

AGARD Report 99 666.762 AGARD Report 99 666. 762 North Atlantic Treaty Organisation, Advisory Group North Atlantic Treaty Organisation, Advisory Group for Aeronautical Research and Development 2a9g2:3e3c5c for Aeronautical Research and Development 2a9g2:3e3c5c CERMETS AS POTENTIAL MATERIALS FOR HIGH-TEMPERATURE CERMETS ASPOTENTIAL MATERIALS FOR HIGH-TEMPERATURE SERVICE SERVICE 0. A. Sandven. O.A. Sandven. 1957. 1957. 24 pages, incl. 15 Figs., 9 Refs. 24 pages, Incl. 15 Pigs., 9 Refs.

Some experimental results on the system NbC-TiC Ni Some experimental results on the system NbC-TiC Ni are reported. are reported.