Effect of alloying on the structural ni cr-nb

EFFECT OF ALLOYING ON THE STRUCTURAL
OF NI- W Co- W COMPOSITE MATERIALS
B. A. Klypin, A. M. Maslov,
and S. B. Maslenkov
STABILITY
UDC 669.24'25:669-419.4
The mechanical properties of heat-resistant composite materials depend to a considerable extent on the
character and intensity of the physicochemical interaction between the filament and the matrix during prepa-
ration and operation of the material. Subsequent reactions that impair the mechanical properties of the com-
posite as compared with the theoretical values have been observed tn various nickel and cobalt alloys rein-
forced with tungsten filament - lowering of the resistance of the filament to rec ry stallization [1-6]. solution of
the filament [4, 7], formation of interlayers of brittle phases at the interface [1-3, 5-10], and diffusional poros-
ities near the interface [6]. The intensity and relative effect of each of these reactions on the properties of
the composite depend on the chemical composition of the components and the temperature-time conditions of
their interaction.
We investigated the effect of the composition of nickel and cobalt alloys on the structural stability of
composite materials reinforced with tungsten filaments.
Three groups of alloys were investigated (Table 1): 1)nickel, Nlchrome, and ternary alloys based on
Nichrome containing around 10 at. ~ of the third element; 2) commerical oxidation-resistant and heat-resistant
nickel alloys alloyed to different extents; 3) cobalt and cobalt-base alloys.
In addition lo alloys KhN70Yu, KhN45Yu, and ~21893 listed in Table 1, we used complex alloys of the
ZhS6K and TsZh24 ts-pes containing Cr, Mo, W, Co, AI, and "i't that differed from the other alloys in their high
carbon concentration (0.13-0.15%).
Commerical unalloyed tungsten filament > 99.95% pure (I'U VM 2-529-57) was used as reinforcement.
All materials were produced in the form of rods by pouring the matrix material over the reinforcing material
2 mm indiameter and subsequent extrusion of the castings [11]. The molten matrix material was heated ~ 100°C
above the melting point before casting. The castings were turned to a diameter of 77 mm and pressed at 1150-
1180°C in a hydraulic press. The diameter of the filament in the extruded rods was ,,, 0.5 mm; the filament con-
stituted ~33 vol.% of the composite.
Measurements of the filament diameter after casting showed that the diameter of the tungsten rod de-
creases no more than 0.06 mm due to solution in the molten nickel and nickel-base alloys. However, when cobalt
and cobalt alloys are poured over the rod its diameter decreases 0.3 and 0.16 ram, respectively. The tungsten
rod retains its deformed structure after pouring of all matrix materials.
The effect of the interaction of tungsten rod with the matrix during preparation of the composite on the
ductility of the filament at low temperatures was determined in bending tests. The filaments were etched out
of the extruded rods. The filaments from nickel alloys underwent brittle fracture at 20° (bending angle a = 0);
the filaments etched out of the Co-18Cr-15Walloy had some ductility (ce ~45°).
To investigate the interaction between the filament and the matrix during prolonged operation at high
temperatures the samples were annealed in evacuated quartz ampules at 1100° for 100, 300. and 1000 h. After
annealing, the samples were subjected to metallographic analysis and the chemical composition of the transition
zone near the filament-matrix interface was determined by means of the CAMECA Microprobe analyzer.
I. P. Bardin Central Scientific-Research Institute of Ferrous Metallurgy. Translated from Metallove-
denic i TermichcskayaObrabotke Metallov, No. 5, pp. 6-11, May 1977.
]This matertal is protected by copyright registered in the name of Plenum Publishing Corporation, 227 West 17th Street, New York, N.Y. 1001l. ?¢}9part
of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by an>' means, electronic, mechanical, photocopying,
microfilming, record#tg or otherwise, without written permission of the publist or. A copy of this article is available from the publisher for S 7.50.
343

TABLE 1
Material
Composition, %
NI Cr W others
yt (pure) ..........
NI -- 20 Cr . . . . . . . . . .
NI -- 18 Cr-15W .......
NI -- 16 Cr-26 W ........
NI -- 18 Cr-16 Mo ......
NI -- 20 Cr-10 Fe .......
NI -- 20 Cr-8 TI .......
NI -- 19 Cr-I5 Nb ......
N[ -- 21 Cr--5 A| . . . . .
co--(pure) . . : . : ....
Co -'- -18Cr--15 W . . . . . . .
81,0
99.9 1~,80
16,60
69,9S
67,70 119,5018'20
72,55 I 19,03
69,95 / 19,03
-- I~87
I~,40
15,30 Mo
10,7 Fe
7,05 TI
13,70 Nb
4,80 A1
99.9 Co
I o01 Rem. Co
KhN70Yu Base 27,2 - 3,~ m;. . . . . . . . <1 Fe
35 4 Fe;
KhN45Yu.......... Base 15,5 - 3,4A;
0,07 C
Base 15,~EI893 .......... 8,80
4,38 MO;
1,42 AI;
1,40 TI;
0,04 C
Note. Carbon content< 0.01% (except where
~ven); St, 0.02-0.03~.
TABLE 2
Compostdon of matrix
NI . . . . . . . . . . . .
NI-29 Cr . . . . . . . . .
NI- I8 Cr-15 W .....
NI--16 Cr-26 W
N,--200-10V~ :::::
NI-20 Cr--8 TI ......
Ni--18 Cr--16 Mo .....
NI--19 Cr-15 Nb .....
NI-21Cf--5 AI ......
KhN70Yu
KhN45Yu
zhS6K
T s Z h 2 4
co . . . . . . . . . . . .
Co--lB Cr-15 W .....
Depth of re- Width Develop-
crystallized Iof in- Iment of
zone, p (an- terlayer, diff. poros-
nealed 1]00"1 ~ _l!_ty__
(annealed at 1100"
300 h) for 1000 h)
>250
>259
160 - > 259
30-80
I00-- >7,59
~3o - >2sO
0--I00
I00 -- > 259
90 -- > 259
50--70
50--I00
30--100
30--60
0
0
_ Very
strong
: Strong
Moderate
4o-so We~k
20230_ Moderate
20--40
1O-- 13¢.~*r* : --
70180
*Matrix has biphase structure, but no inter-
layer formed.
~Recrystallized zone begins at a depth of
70-100/~ and occupies entire central section
of filament 300-340/z in diameter.
$ Complete solution of almost entire fila-
ment.
** After annealing at 1100 ° for 300 h.
The rate of the interaction between the filament and the matrix was determined from the extent of re-
crystallization of the filament, the formation of intermediate phases at the interface, the solution of the filament
in the matrix, and the formation of diffusional porosities. Some results of these analyses are ~ven in Table 2.
In all materials with a nickel matrix a zone of accelerated recr3,stallization of the filament was observed.
The width of this zone increased with annealing time. The recrystallization rate of the filament was highest
with a matrix of pure nickel and somewhat lower with a Nichrome matrix. Alloying of Nichrome with iron,
titanium, aluminum, and especially tungsten and niobium slows down the recrystallization process consider-
ably (Table 2). With a matrix of a complex alloy of the ZhS6K and TsZh24 t3-pes the recrystallization rate of
the filament is near that with a matrix of Ni-16Cr-26W and Ni-19Cr-15Nb.
344

• "',= • ' '.,d
Fig. I. Microstructure of the fila-
ment in a composite with a matrix of
alloy Co-18Cr-15 W after anneal-
ing at 1100 ° for 300 h. 100x.
...:,
2"
i;
Fig. 2. Diffusional porosity in composite materials Ni +W (a) and Ni-
18Cr-15Mo+W (b) after annealing at 1100 ° for 1000 h. 100x.
~0
66
a
o° ',
8a~
~e, i !0
U ~0
0
40 a OO 8a 170 160
...... T ---i
b
~o 0 00 8# !70
I
l05'
Distance from boundary
d e f
......I NL
I[c/-
C
~0 b'O
Fig. 3. Variation of the concentrations of elements near the
interface in composites with different matrices after anneal-
ing at 1100° for 1000 h. a) Nickel; b) NI-20Cr; c) l~'i-21Cr-
5AI; d) Co-18Cr-15W; e) Ni--18Cr--15Mo; f) NI-16Cr--26W.
345

The stability of the deformation structure of the tungsten filament is highest in a matrix of cobalt and the
Co-18Cr-15W alloy (Fig. 1 and Table 2~. Recrystallized areas randomly distributed through the section of the
filament occur in the filaments of composites with a matrix of these alloys only after annealing for 1000 h.
Consequently, diffusional interaction with cobalt and the Co-18Cr-15W alloy evidently has a negligible effect
on recrystaUization of the tungsten filament. It should be noted that recrystallization of the filament similar
to that in composites with a nickel matrix was observed in a matrix of cobalt alloy L--605 [1], the composition
of which resembles that of Co-18Cr-15W, but with 10~ Ni.
Thus, the data obtained indicate that accelerated recrystallization of tungsten filaments in a matrix of
nickel and cobalt is due to the presence of nickel in the matrix.
After prolonged annealing at 1100° the diameter of the filament in composites with a nickel matrix re-
mains almost unchanged; intensive solution of the filament occurs in a matrix of Co-18Cr-15W, and especially
in pure cobalt.
The development of diffusional porosities during prolonged holding at high temperatures, leading to
weakening of the material, was determined qualitatively by examining the unetched section in a light micro-
scope. Zones of porosity usually located at a distance of 40-100 ~ from the interface took the form of continu-
ous rings around the filament in etched composites with a matrix of nickel, Nichrome, Ni-20Cr-16Fe, and
Ni-18Cr-16Mo (Fig. 2). When the Ni-Cr solid solution is alloyed, especially with elements with low diffusion
mobility (molybdenum, for example}, the porosity decreases considerably and is generally not observed in a
biphase matrix {Table 2).
The results of microprobe analysis of several composites are shown in Fig. 3. These data indicate that
diffusion of elements from the matrix into the filament is negligible. The tungsten concentration in the transi-
tion zone adjoining the filament varies with the composition of the matrix and decreases considerably when
Nichrome is alloyed with aluminum, molybdenum, and especially tungsten. An interlayer of intermediate
phases is observed in composites with a matrix of Nichrome alloyed with 10 at. % Ti and 1~%,complex alloyed
nickel alloys, and cobalt alloys (Table 2}.
In the composite with a Co-18Cr-15W matrix the hardness of the intermediate phase (Fig. 1) is Its0 =
750-790 and the chemical composition (6.5-8.6~ Cr, 28.2-31.3% Co, and 60.4-64.5~ W) matches that of ~ phase
based on CoT(W,Cr)6. When the annealing time is increased from 100 to 1000 h the thickness of the interlaTer
of ~ phase increases from ,,, 30 to ,,, 80 p.
The interlayers of intermediate phases are much thicker with a nickel matrix than with a cobalt matrix
(]?able 2). Ni3Tt and Ni3Nb are formed at the interface in composites with a matrix of Ni-20Cr-8Ti and Ni-
19Cr-15Nb.
In the composite with a matrix of alloy TsZh24 an interlayer is formed with a composition (metallic
elements~ close to that of alloy 58W- 17Ni- 10Cr- 3Co- 2Mo- 1 (Nb + Ti + A1}, with microhardness Hs0 ,,, 1200.
An intermediate phase of similar composition and hardness observed in samples of the same material annealed
at 950° for 3500 h was investigated earlier by analysis of the section in the Microflex apparatus with use of
Kc~Cu redtation. It was found* that this phase has a lattice of binary carbide MsC. Comparison of the micro-
probe and diffractometric data leads to the conclusion that the intermediate phase in the composite of TsZh24 +
W is the binary carbide (Ni, Cr, Co}4(W, Mm2C.
In the composite with a matrix of ZhS6K annealed at 1100 ° for 1000 h there were two transition zones
at the interface- an even inner zone A 15-20 ~ wide with microhardness Hs0,-, 1200 and outer zone B uneven
in width (5-25 ~) with microhardness H50,,,420 (Fig. 4}. The composition of zones A and B (in terms of metal-
lic elements~ was close to that of alloys 57XV-17Ni-llCr-6Co-4.5Mo-l{Tt+A1} and 761~i-6Co-SW-5Ti-
5A1-2.5Cr-0.SMo, respectively. These data indicate that phase A is the binary carbide (Ni, Cr, Co}4 (W,hIo}2C
with a somewhat different ratio of alloying elements than in the similar phase of the TsZh24 + W composite,
while phase B matches -y' phase (Ni, Co}3(Ti, A1, W~.
In a study of Nlmocast 258 and 713S alloys reinforced with tungsten filaments, which are similar in
terms of carbon, titanium, and aluminum to the ZhS6K alloy, double interlayers of intermediate phases were
also observed. They were not identified, although the hardness and composition match those of the ZhS6K + W
composite.
*The analysis was made in the x-ray laboratories of the Central Scientific-Research Institute of Technolo~
and Machine Construction (rsNIITMASh}.
346

A B
.~.~.~
Fig. 4. Microstructure of composite
ZhS6K + W after annealing at 1100°
for 1000 h. 320×.
Thus, the data obtained indicate that no interlayer of intermediate phase is formed during the interac-
tion of tungsten filament with a matrix of heat-resistant wrought alloys of the I~I1893 t)~pe containlng ~ 0.057c
C and < 4% (Tt + A1). In a matrix of similar composition but with a high carbon concentration (more than
~ 0.10~,) an interlayer is formed of the binary carbide t)~pe (Ni, Cr, Co)4(W, Mo)2C. In a more highly alloyed
matrix of the ZhS6K type, with an elevated concentration of titanium and aluminum along with carbon, double
interlayers of carbide phase and "/' phase are formed.
Comparison of the data concerning the effect of alloying of the nickel matrix on the recrystallizafion
and formation of porosities with results from microprobe analysis points to a direct relationship between
these processes and the rate of the diffusional interaction between the filament and the matrix. The interac-
tion can be slowed down by alloying of the Ni-Cr matrix with refractory metals of groups VA and VIA, espe-
cially tungsten. Combined alloytngwith tungsten and molybdenum (,,,5 at. % total) has a similar positive effect,
along with aluminum, titanium, cobalt, and other elements.
For a matrix of cobalt alloy with chromium and tungsten the interaction with the tungsten filament dif-
fers from that with a nickel-base matrix- a relatively rapid interaction occurs with formation of CoT(W. Cr)t;
diffllsion of elements from the matrix to the filament and tungsten to the matrix is evidently negligible. There-
fore, the principalreason for the reduction in the strength of a composite with a cobalt matrix is the intensive
solution of the tungsten filament; rapid recrystallization of the filament and diffusional porosities are not ob-
served. Thus, the cobalt matrix must be alloyed to reduced its dissolving effect.
CONCLUSIONS
I. Composites with a Ni-Cr matrix are characterized by embrittlement and negligible solution of the
tungsten filament. An effective method of slowing down recrystallization of the filament and eliminating pore
formation is alloying of the matrix with refractory metals of groups VA and VIA, especially tungsten, and also
the use of complex alloys for the matrix such as alloys of the ZhS6K and TsZh24 tsq~e.
2. With a cobalt matrix, unlike a nickel matrix, the tungsten filament is embrittled much less, and no
acclerated recrystalllzation occurs. However, the serious drawback of this type of matrix is the intensive
solution of the filament during holding at high temperatures.
3. No interlayer of intermediate phase is formed at the interface in a matrix of heat-resistant alloys
containing up to ,,,0.05~ C and < 47o (rl + Al) after annealing at 1100 ° for I000 h. When the carbon concentra-
tion is raised to ,~ 0.107o an interlayer of carbide phase of the M~C type is formed, and with > 77o (Ti + A.l) a
double interlayer of earbide phase and T' phase. An interlayer of Co?(W, Cr~ I is formed with a cobalt alloy
matrix.
347

LITERATURE CITED
1. R.A. Stgnorelli, D. Petrasek, and J. W. Weeton, "Reactions on surfaces of separation in metals rein-
forced with metallic and ceramic fibers," in: Modern Composite Materials, Addison-Wesley, Reading,
Mass. (1967).
2. B.A. Klypin, A. M. Maslov, and S. B. Maslenkov, nReinforcement of heat resistant alloys with filaments,"
Metalloved. Term. Obrab. Met., No. 8, 2 (1971}.
3. A. Dean, J. Inst. Met., 95, No. 3, 79 (1967}.
4. V.F. Kotov, N. M. Fonshtein, and V. I. Shvarts, "Heat resistant composite material: Nfchrome-tungsten
filament," Metalloved. Term. Obrab. Met., No. 8, 20 (1971).
5. A.N. Savchuk et al., "Structural changes in composite materials with iron-base and rdckel-base matrices,"
Metalloved. Term. Obrab. Met., No. 8, 63 (1974}.
6. S.A. Golovanenko et al., "Interaction between the filament and the matrix in nickel alloys reinforced with
tungsten filaments," Ftz. Khim. Obrab. Mater., No. 3, 42 (1975}.
7. F.P. Banns et al., "Composite materials: Ntchrome-molybdenum, tungsten," Metalloved. Term. Obrab.
Met., No. 8, 6 (1971}.
8. I.N. Frantsevich, D. M. Karpinos, and V. A. Bespyatyi, "Stability of the structure of nlckel-base rein-
forced composites," Poroshk. Metall., No. 12, 60 (1969}.
9. A.T. Tumanov et al., "Heat-resistant composite materialbased on nickel VKN-I,' in: Metallic Composite
Materials [in Russian], ONTI VIAM (1972), p. 51.
10. A. Morris, Fibre Science and TechnologT, 3, No. 1, 53 (1970}.
11. S.A. Golovanenko et al., nHeat resistant composite material prepared by pouring the matrix over the
reinforcement," in: Structure and Properties of Heat Resistant Metallic Materials [in Russian], Izd.
Akad. Nauk SSSR-TsNIITMASh, Moscow (1970), p. 69.
MECHANICAL PROPERTIES OF SEMIFINISHED
OF DISPERSION-HARDENED NICKEL
V. I. Lyukevich, M. Kh. Levlnskaya,
and V. M. Romashov
PRODU CTS
UDC 669.24:620.17:620.18
The heat resistance of semifinished products of dispersion-hardened alloys can be improved by deforma-
tion and heat treatment [1,2]. Since the properties of dispersion-hardened alloys vary with the type of deforma-
tion, it is of interest to determine the effect of additional deformation and subsequent annealing on the structure
and properties of semifinished products with a given level of the original mechanical properties.
Bars 12.3 mm in diameter and sheets 0.85 mm thick of dispersion-hardened nickel containing 3 vol.~
HfO2 were subjected to additional deformation [3]. The bars were obtained by extrusion of powder compacts
at 1100-1050°C and subsequent cold drawing, with total reduction of 67~, and then annealed at 1400 °. The
sheets were obtained by cross rolling extrusions at 1000-900 °, with total reduction of 83~. The sheets were
annealed at 1350 ° and then cold rolled with total reduction of 50~, after which they were annealed at 1200 ° to
remove strain hardening.
The semiftnished products were subjected to additional cold deformation and annealing for 1 h at temper-
atures from 400 to 1400 °. The bars were drawn with reductions of 30, 50, and 67%, and upset along the axis,
with deformation of 10, 50, and 75~. The sheets were rolled in the direction of preliminary deformation with
reductions of 10, 30, and 50~.
The structure was investigated by means of light metallography and by x-ray analysis. After electro-
All-Union Institute of Aviation Materials. Translated from Metallovedenie i Termlcheskaya Obrabotka
Metallov, No. 5, pp. 11-15, May, 1977.
This material is protected by copyright registered in the name of Plenum Publishing Corporation, 227 |¢est 17th Street, New York, N. Y. 10011. No part
of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying,
microfilming, recording or otherwise, without written permission of the publisher. A copy of this article is available from the publisher for $ Z 50.
348

Effect of alloying on the structural ni cr-nb

More Related Content

What's hot (18)

Similar to Effect of alloying on the structural ni cr-nb (20)

Recently uploaded (20)

Effect of alloying on the structural ni cr-nb