Ni-Cr-Fe

The ternary diagram of Ni-Cr-Fe is one of the most used ternary diagrams in history. The two types ofalloys covered here from the Ni-Cr-Fe diagram are Stainless Steel and Inconel (tm).

Stainless Steel

There are a vast number of types of Stainless steel. A metal alloy with a Chromium content greaterthan 11.5 % and an Iron content greater than 50 % is called a stainless steel. The stainless steels are

broken into three major classes:

1. Chromium (11.5-17%) -iron alloys with carefully controlled carbon content. Can be heat treated to

a magnetic martensite structure and are therefore known as martensitic stainless steels.

2. Chromium (17-27%) -iron alloys with low carbon content. Nonhardenable by heat treatment. Their

crystal structure is magnetic ferrite and therefore are known as ferritic stainliess steels.

3. Chromium (16-26%) Nickel (6-22%) -iron alloys with low carbon content. Nonhardenable by heattreatment. Crystal structure of nonmagnetic austenite so are therefore called austenitic stainless steels.

The following table compares the composition and some basic properties of various types of stainless

steel.

A Comparison of Stainless Steels

Type

of

Steel

%

Nickel

%

Chromiium

%

Carbon

%

Manganese

%

Silicon

%

Nitrogen

Corrosion

mpy (1)

Melting

Range F

Young's

Modulus

x 10^6,psi

201 3.5 - 5.516.0 -

18.0

0.15

max5.5 - 7.5

1.0

max

0.25

max20

2550 -

265028.0

301 6.0 - 8.0 16.0 -18.0

0.15max

2.0 max 1.0max

0 12 2550 -2590

28.0

302 8.0 - 10.017.0 -

19.0

0.15

max2.0 max

1.0

max0 10 - 18

2550 -

259028.0

304 8.0 - 10.518.0 -20.0

0.08max

2.0 max1.0max

0 6 - 122550 -2650

28.0

30919.0 -

22.0

24.0 -

26.00.2 max 2.0 max

1.0

max0 5 - 9

2550 -

265029.0

(1) Corrosion rate is in mils per year. The test was performed in 65% Nitric acid at 245 F.

(2) Table references

Types of Stainless steel and specific uses of each.

Stainless type 201

Stainless type 301Stainless type 302

Stainless type 304Stainless type 309

Inconel (tm)

Inconel (tm) is a specialty alloy that uses higher percentages of Nickel and Chrome than Stainless steel,

as well as many other elements in small quantities. It is actually a trademark name of Inco AlloysInternational and is in a group of metals known as the Nickel based super alloys. These small additions

of other elements is solid-solution hardening. It is quite expensive and therefore usually reserved forapplications when some type of stainless steel won't suffice. The following tables compare Inconels

(tm) properties.

A Structural Comparison of Inconel (tm) Alloys

Type%Ni

%Cr

%C

%Mn

%Si

%Fe

%S

%Cu

%Al

%Ti

%P

%Co

%Nb

%B

%Mo

60072.0

min

14.0

-17.0

0.15

max

1.0

max

0.5

max

6.0

-10.0

.015

max

0.5

max0 0 0 0 0 0 0

60158.0

-

63.0

21.0-

25.0

0.1

max

1.0

max

0.5

maxbal

.015

max

1.0

max

1.0-

1.7

0 0 0 0 0 0

62558.0min

20.0-

23.0

0.1max

0.5max

0.5max

5.0max

0.015max

00.4max

0.4max

.015max

1.0max

3.15-

4.15

08.0-

10.0

50.0 17.00.08 0.35 0.35 .015 0.3

0.2 0.651.0

4.75.006

2.8

718 -

55.0

-

21.0

max max max bal max max -

0.8

-

1.15

.015 max -

5.5

max -

3.3

800 32.5 21.00.1max

0.8max

.008max

46.0 0 0.4 0.4 0.4 0 0 0 0 0

(1) Table references

Corrosion of Inconel (tm)

One outstanding characteristic of high-nickel alloys, like Inconel (tm), is their good resistance to a widevariety of corrosives. With few exceptions, high-nickel alloys do significantly better than martensitic,

ferritic, and austenitic stainless steels in corrosive environments.

A Comparison of Inconel (tm) Properties

TypeYield Strength

70Fksi

Melting

Range FRupture Strength; 100h at ____F, ksi

600 41.3 2471 - 2579 1600, 5.3

601 49.0 2471 - 2579 1600, 7.0

625 71 2300 - 2435 1600, 10.5

718 172 2300 - 2435 1200, 100

800 36.3 2471 - 2525 1800, 21

(1) Table references

The uses of Inconel (tm) are specific and quite costly:

Piping on Nuclear Reactors

Piping on Steam Generators

A Heat Exchanger on an unmanned ariel vehicleWell Thermometers in high temperatures and pressures

Andrew Johnson 4/28/96

http://www.eng.vt.edu/eng/materials/classes/MSE2094_NoteBook/

96ClassProj/examples/nicrfe.html

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