Type
Analysis
|
Element
|
Min
|
Max
|
|
Carbon
|
0.15
|
0.20
|
|
Manganese
|
--
|
0.50
|
|
Silicon
|
--
|
0.50
|
|
Phosphorus
|
--
|
0.03
|
|
Sulfur
|
--
|
0.03
|
|
Chromium
|
12.00
|
14.00
|
|
Nickel
|
1.80
|
2.20
|
|
Molybdenum
|
--
|
0.50
|
|
Tungsten
|
2.50
|
3.50
|
|
Iron
|
Balance
|
Description
Greek Ascoloy (418) is a
hardenable chromium-nickel-tungsten martensitic alloy that is
designed for services at temperatures up to 1200 °F in highly
stressed parts.
This steel is an extremely deep-hardening grade
and is used where slightly superior creep strength and resistance to
tempering and stress-corrosion cracking are desired in addition to
the general properties of the 12% chromium stainless steels. Typical
applications are steam turbine buckets and blades as well as
compressor parts in gas turbines and high temperature bolts.
Corrosion
Resistance
Greek Ascoloy has good
resistance to scaling and oxidation at temperatures up to 1400 °F.
It resists atmospheric corrosion, weak organic acids and oxidizing
acids. It has best corrosion resistance in the hardened and tempered
condition.
Physical
Properties
Specific gravity..............................................7.874
Density
lb/in(3)........................................................0.2864
kg/m(3)....................................................... 79164
Electrical resistivity-77 °F (25.0 °C)4
ohm-cir mil/ft............................................... 4754
microhm-mm................................................ 7904
Melting range °F.....................................600/27004
°C ................................. 1427/1482
Modulus of Elasticity in
Tension (E)
|
Temperature
|
psi
x 10(6)
|
MPa
x 10(3)
|
|
°F
|
°C
|
|
70
1000
1100
|
21.1
538
593
|
29.0
21.5
17.0
|
199
148
117
|
Coefficient of
Thermal Expansion
|
Temperature
|
Coefficient
|
|
80 °F to
|
26.7 ° C to
|
10(-6)/° F
|
10(-6)/° C
|
|
200
400
600
800
1000
1100
1200
|
93
204
316
427
538
593
649
|
5.83
6.12
6.20
6.37
6.52
6.62
6.63
|
10.5
11.0
11.2
11.5
11.7
11.9
11.9
|
Heat
Treatment
Annealing
Greek
Ascoloy (418) is process annealed by heating to 1300 °F, holding
at temperature approximately 4 hours, and air cooling. The resultant
hardness is approximately 280 BHN. To obtain maximum softness and
complete relief of stresses, a cyclic anneal is required. This
treatment consists of heating to 1450 °F for 2 to 4 hours
followed by furnace cooling to 800 °F least 200 °F. The
material is then reheated to 1250/1300 °F for a minimum of 12
hours and air cooled. The resultant hardness is approximately 255
BHN.
Hardening and
Tempering
An austenizing temperature of 1700/1800 °F is
generally used to harden Greek Ascoloy (418) followed by quenching in
either oil or air depending upon section size and design. Heavy
sections, or parts of intricate design are usually preheated at
1200/1400 °F prior to hardening. The resultant hardness is
approximately 448/472 BHN.
Tempering should be done as soon as
possible following the hardening treatment. The effect of tempering
temperature on hardness after oil treating from 1750 °F is shown
below.
|
Tempering
Temperature
2
hours
|
Hardness
BHN
|
|
°F
|
°C
|
|
1050
1150
1200
1250
1300
|
566
621
649
677
704
|
364
302
297
285
280
|
Workability
Hot Working
Greek
Ascoloy is readily hot worked in the temperature range 1750/2150°F.
Large sections should be preheated to 1200/1400°F prior to
heating to forging or rolling temperature. Forgings should be cooled
slowly from hot working temperatures.
Machining
Greek
Ascoloy is readily machinable in the annealed condition and is
comparable with types 403 and 410.
Welding
The
air-hardening qualities of this steel favor preheating to 400/600°F.
Annealing as soon as possible after welding is recommended because of
the air-hardening characteristics which make the heat affected zone
hard and brittle. An austenitic steel filler rod such as Type 310
stainless is recommended in order to obtain sufficient ductility in
the weld.
Typical
Mechanical Properties
Typical Room
Temperature Tensile Properties
Specimens heat treated by
hardening at 1750°F and oil quenching followed by tempering at
temperature indicated for 4 hours and air cooling.
|
Tempering
Temperature
|
Yield
Strength
|
Ultimate
Tensile
Strength
|
%
Elongation
in
2"
|
%
Reduction
of
Area
|
|
°F
|
°C
|
0.2% offset
|
0.02% offset
|
|
|
|
ksi
|
MPa
|
ksi
|
MPa
|
ksi
|
MPa
|
|
500
600
700
800
900
1000
1100
1200
1300
|
260
316
371
427
482
538
593
649
704
|
175
180
183
185
165
137
120
108
98
|
1207
1241
1262
1276
1138
945
827
745
676
|
150
160
165
168
158
140
123
107
87.5
|
1034
1103
1138
1158
1089
965
848
738
603
|
209
212
217
217
197
165
145
135
125
|
1441
1462
1496
1496
1358
1138
1000
931
862
|
18.0
17.0
16.0
16.0
17.0
17.5
18.0
20.0
22.0
|
53.0
55.0
56.0
57.0
58.0
59.0
60.0
61.0
62.0
|
Typical Short-Time Elevated Temperature Tensile Properties
Specimens heat-treated by hardening at 1750°F (954°C), oil quench followed by tempering at 1050°F (566°C), air cool.
|
Test
Temperature
|
Yield
Strength
0.2% offset
|
Ultimate
Tensile
Strength
|
%
Elongation
in
2"
(50.8 mm)
|
%
Reduction
of
Area
|
|
°F
|
°C
|
ksi
|
MPa
|
ksi
|
MPa
|
|
70
500
600
800
900
1000
|
21
260
316
427
482
538
|
135
129
124
112
101
84
|
931
889
855
772
696
579
|
160
150
144
127
113
95
|
1103
1034
993
876
779
655
|
16
12
11
10
13
17
|
45
43
43
43
52
64
|
Specimens heat treated by hardening at 1750°F (954°C), oil quench followed by tempering at 1200°F (649°C), air cool.
|
Test
Temperature
|
Yield
Strength
0.2% offset
|
Ultimate
Tensile
Strength
|
%
Elongation
in
2"
(50.8 mm)
|
%
Reduction
of
Area
|
|
°F
|
°C
|
ksi
|
MPa
|
ksi
|
MPa
|
|
70
900
1000
1100
|
21
482
538
593
|
115
82
70
55
|
793
565
483
379
|
140.8
100
84
67
|
971
689
579
462
|
21.0
16.0
22.0
30.0
|
58.0
63.0
74.0
83.0
|
Room Temperature Impact Strength - Izod V-Notch
Specimens heat treated by hardening at 1750°F (954°C) and oil quenching.
|
Tempering
Temperature
|
Impact
Strength
|
|
°F
|
°C
|
ft-lb
|
J
|
|
500
600
700
800
900
1000
1100
1200
1300
|
260
316
371
427
482
538
593
649
704
|
19
16
10
9
10
17
40
77
65
|
26
22
14
12
14
23
54
104
88
|
Hot Hardness
Specimens heat treated by hardening at 1750°F (954°C), air cool followed by tempering at 1000°F (538°C), 2 hrs., air cool.
|
Test
Temperature
|
Hardness BHN
30 min. at
Temperature
|
|
°F
|
°C
|
|
700
800
1000
1200
|
21
427
538
649
|
352
312
290
176
|
Stress Rupture
Properties
Specimens heat treated by hardening at 1800°F,
air cool followed by tempering at 1050°F, 2 hrs, air cool.
|
Test
Temperature
|
Stress
for Rupture in
|
|
°F
|
°C
|
10 hours
|
100 hours
|
1000 hours
|
|
ksi
|
MPa
|
ksi
|
MPa
|
ksi
|
MPa
|
|
1000
1100
1200
|
538
593
649
|
65
42
23
|
448
290
159
|
52
33
19
|
359
228
131
|
41
22
11
|
283
152
76
|
| 
