TECHNICAL INFORMATION

MODERN M A T E R I A L S FOR GAS T U R B I N E BLADES AND D I S C S

(UDC 669.14.018.45 : 682.135)

E. E. L e v i n

Polzunov TsKTI Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 1,

pp. 67-70, January, 1966

In recent years the number of pumping stations has increased greatly along with the development of gas pipe-

lines and the installation of powerful gas turbines for peak production at electric power stations. The main parts in these pumps require heat resistant materials which can be operated for 50,000-100,000 h. In some cases the work-

ing life of turbine blades is as low as 10,000 to 20,000 h under the highest permissible working temperatures. The

turbine blades and discs must be made of particularly strong materials since they are operated under severe conditions.

To withstand the influence of prolonged exposure to high temperatures the metal must have a stable structure,

high deformability, and (particularly important) low sensitivity to stress concentrators.

The increase in the temperature of the gas to 800-850~ and, correspondingly, of the temperature of the turbine

blades to 750-800~ increases the danger of breakage as the result of general and pitting corrosion and thermal fatigue.

There are many alloys manufactured at home and abroad which have high heat resistance at room temperature and

at workitlg temperatures and which are scale resistant [1-3J, but the selection of materials for turbine blades is

rather difficult.

1Kh12VNMF steel and the austenitic steels 3Khl9NgMVI3T and KhN35VT (EI612 and EI612K) are usually used

for blades and discs which are operated at 580-650~ An increase of the working temperature to 700-750~ leads

to the necessity of using nickel alloys - KhNSOTBYu (Et607, EI607A), KhNTOVMYuT, and Kh15N65V10M5TYu. The

EIg07A (KhNSOTBYu) alloy is used for blades in mass produced turbines operated at temperatures up to 200-720~

The addition of niobium to these alioys ensures uniform grain size and renders the mechanical properties

highly isotropic, which makes the ~I607A alloy a promising material for the manufacture of highly stressed discs.

The stronger KhTOVMYuT and Kh15N65V10M5TYu al!oys are used for blades operated at 720-750~ The

large total amount of molybdenum and tungsten in these alloys makes it difficult to manufacture large ingots and

forgings with large cross sections. Zonal liquation develops and, as the result, the properties of the different parts

are different. The uniformity of the properties can be increased by multistage heat treatment. This t reatment is

the most effective in the case of the KhN65VMTYu alloy. This alloy has very stable properties during prolonged

use and possible short periods of over-heating.

Further increase in the working temperature of blades to 800~ with possible short periods of over-heating

to 850~ makes it necessary to use alloys of a similar type but containing a high concentration of aIuminum. Ex-

haustive studies showed that the most promising alloy for these conditions is the EI826 altoy [1]. This alloy has

TABLE 1. Concentration of Different Elements in Nickel Alloys [1, 4]

Alloy No.

KhN80TBYu * ,. KhN80TBYu (EI60JA) * KhNTOVMYuT KhN65VMTYu EI826

<0,08 <0.08

0.10--0.16 <0.08 40.12

Chemical com ~osition, %

Cr

15--18 15--17 14--15 15--17 13--16

Ti

1.8--2,3 1,4--1.8 1.0--1,4 1".2--1,6 1,7--2.2

AI

0.5--1 0 0.5--1.0 1,7--2.2 1,2--1,6 2_4--2.9

No

ao--5.o 4.0--5.0 2.5--4.0

w

4.0--6 0 8.0--10 0 5.0--7.0

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TABLE 2. Mechanical Properties of Nickel Alloys

Alloy No.

KhN80TBYu

KhN65VMTYu

J EI826

Aging conditions

TcmP., Time, ~ h

& 700 5000

Testing /-~0,~ I

temp. , C l kg /mm 2

20 650 700 650 700

60 105 55 75 50 68 60 90 38 63

26 lo

18 15

770 5000

20 700 750 750

67 55 52 42

105 80 78 75

30 20 20 29

750 800

5000 5000

20 700 800 750 800

62 52 50 60 45

107 95 80 95 65

17 23

12

32 12 7

18 18

35 30 23 35

16 27 25 16 20

a H , kgm/cm 2

10 10 12

10 12 12

3,5 6 7

7

TABLE 3. Resistance of Nickel Alloys to Prolonged Exposure to High Temperatures

A l l o y No.

KhN80TBYu KhN80TBYu (EI607A) KhN~0VMYuT ~hN65VMTYu EI826

O'prol, k g / m m 2 a t t he f o l l o w i n g t e m p e r a t u r e , OC

t 30/28 20/18 - - 25/23

25/24 50/47 38/37

800 j gSo

_ _ ) / _ _

lSTi~ t [ -- 18f20 --~13 - - 30/28 18/16/ 1U9

Note: The numerator refers to 5,000 h tests, the denominator to 10,000 h tests.

TABLE 4. Mechanical Properties of Alloys

t Aging conditions Heat t rea tment - -

Temp. , Time, conditions ~ h

Testing temp. , ~C

I ':0,2

k g / m m 2 a H , k g m / c m 2

1080 ~ C 6 hq-lO00 ~ C 2 h ~ - 7 5 0 ~ C

20 h

1120 ~ C 8 h+lO0O ~ c 4 hq-800 o C

16 h

& 650 700 700

& 650 700 700 750 750

KhNSOTBYu (EI607A)

100-00 10000 10000 10000

20 84 650 60 700 58

20 99 650 78

20 88 700 54

ksg8

- - 20 115 - - 650 96

700 90 10000 20 122 10000 650 108 10000 20 118 10000 700 91 10000 20 110 10000 750 75

47 47 32 38 35 25 54 26 44 22 40 3,0 33 40

70 31 57 27 59 20 80 14 67 19 69 20 57 27 58 25 45 30

47 44 37 30 28 30 45

31 30 23 15 24 19 35 25 40

16

6.0

7.2

9

3.3

3.4

6.5

74

TABLE 5.

Alloy No.

KhN80TBYu Y

(EI607A)

J EI698

KhN77TYuR

KhN70VMYuT

Resistance of Alloys to Prolonged Exposure to High Temperatures

~M

Testing

I temp. , ~

650 700

650 700 750

650 700 750

650 700 750

=prot, k g / m m 2 after the following testing t ime , h

300

54 32

64 52 36

54 40 27

R

500

56 30

61 47 33

50 38 25

m

I000

42 28

58 42 30

45 32 20

'314835 22--25

2000

38 26

56 37 27

42 28 17

274031 20--23

3000

37 25

54 35 25.5

40 27 16

5000 10000

35 33* 23 21"

52 33 21.5*

38* 25--22

15"

25~27 17--20

49* 29 19.0"

33* 20*

11--14"

37* 22--24 16--17

* Extrapolated data.

high plast ici ty at 650-850~ has a low sensit ivity to stress concentrators, and is highly scale resistant. The chemi- cal composit ion, the mechanica l properties, and the resistant of the nickel alloys to prolonged exposure to high temperatures are given in Tables 1-3.

The increase in the working temperature and stress and the need to decrease the britt leness lead to the ne- cessity of using nicket alloys for discs [2, 8],

Investigations of forgings of the KhN80TBYu (EI607A) alloy 450 and 6~0 mm in diameter and stampings of the EI698 alloy 480 and 850 mm in diameter showed that both alloys have good technological properties. The grain size of the forgings is uniform and there is no carbide l iquation or other macrodefects. The KhN80TBYu (EI607A) al loy was used for discs operated at 700-720~ The EI698 alloy, which has a higher aluminum, t i tanium, and niobium concentration and also contains molybdenum (_<0.08% C, 13.0-16.0% Cr, 2.0-2.6% Ti, 0.95-1.45% A1, 1.7-2.5% Mo, 1.6-2.1% Nb, the rest n ickel is recommended for discs operated at 750-760~

Tables4 arid 5 show the mechanica l properties of the alloys after heat t reatment determined on tangential samples. The properties of the metal in the tangential , axial , and radical directions are isotropic. Both alloys are character ized by low sensit ivity to stress concentrators.

Further increase in the temperature and stresses of the blades and discs of gas turbines leads to complex tech-

nological problems related to casting, forging, and stamping of large ingots and articles of highly al loyed alloys which are difficult to deform and problems rela ted to the creat ion of dependable coatings capable of protecting the surface of machine parts against the corrosive action of aggressive gaseous media.

L I T E R A T U R E C I T E D

1. F . F . Khimushin, Heat Resistant Steels and Alloys [in Russian], Moscow, Metal lurgiya (1964). 2. C. Howard, "Metal1 Progress" (1965), Vol. 3. 3. C. Howard, "Meta l l Progress" (1965), Vol. 4.

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