3. AISI 403
Fe - <0.15% C – 12.25% Cr - <0.6% Ni
25 µm 100 µm
Annealed Quenched and Tempered
Annealed (ferrite and carbides) and quenched and tempered (tempered
martensite) microstructures of AISI 402; Vilella’s reagent.
4. AISI 410 – As Cast
Fe - <0.15% C – 12.5% Cr
20 µm
Microstructure of as-cast 410 stainless steel showing a patch of delta
ferrite surrounded by martensite, Vilella’s reagent.
8. AISI 416
Microstructure of 416 free-machining martensitic stainless steel in the quenched and
tempered condition. Etched with Vilella’s reagent. Original at 100X. Note the gray
elongated sulfide inclusions and the elongated “stringers” of delta ferrite (white, see
arrows). The matrix is tempered martensite.
9. AISI 416
Microstructure of 416 free-machining martensitic stainless steel in the quenched and
tempered condition. Etched with Ralph’s reagent. Original at 500X. Note the gray
elongated sulfide inclusions and the elongated “stringers” of delta ferrite (white, see
arrows). The matrix is tempered martensite.
10. AISI 416
10 µm
20 µm
Tempered martensite, delta ferrite and manganese sulfides in
quenched and tempered 416 stainless steel (mod. Fry’s reagent).
11. AISI 416
Microstructure of wrought, Project 70 type 416 martensitic stainless steel
consisting of manganese sulfides (gray), delta ferrite (white) and tempered
martensite (blue and brown) after tint etching with Beraha’s CdS reagent and
viewing with polarized light plus sensitive tint. Original at 500X.
12. 5F (Modified 416)
Fe - <0.1% C – 13.5% Cr - >0.3% S
Grade 5F has 0.5% S and more delta ferrite than Project 70 type 416
martensitic stainless steel; Ralph’s reagent (does not attack sulfides).
13. TrimRite® (AISI 420)
Fe – 0.22% C – 14.25% Cr - <0.6% Ni
Annealed (ferrite and carbide) microstructure of TrimRite
stainless steel; Vilella’s reagent.
14. AISI 420
Fe – 0.30% C – 0.42% Mn – 0.79% Si – 13.8% Cr – 0.27% Ni
Microstructure of type 420 martensitic stainless steel in the quenched and tempered
condition revealing a martensitic matrix and the prior-austenite grain boundaries.
Etched with Vilella’s reagent. Original at 1000X.
15. AISI 420
Vilella’s Reagent Beraha’s Sulfamic Acid Reagent
Carbide networks have been a problem in large sections of hardened
(1038 °C, AC, 177 °C) AISI 420.
16. 13Cr – 4 Ni Martensitic Stainless Steel
Martensitic microstructure of an Fe – 0.03% C – 13% Cr – 4% Ni martensitic
stainless steel etched with Vilella’s reagent.
17. AISI 422
Fe – 0.22% C – 12.5% Cr – 0.75% Ni – 1% Mo – 1% W – 0.23% V
25 µm
25 µm
1900 °F, AC, 1200 °F, AC
Wrought EF-AOD/ESR
1900 °F, AC, 500 °F, AC
Wrought P/M
Tempered martensitic microstructure of wrought P/M (left) and EF-AOD-
ESR (right) 422 stainless etched with Ralph’s reagent.
18. AISI 422
20 µm
100 µm
Segregation streak in a billet (longitudinal plane) of AISI
422 stainless steel revealed using glyceregia.
19. AISI 422
25 µm
Murakami’s reagent (70 °F – 30 s) was used to darken carbides on the
grain boundaries associated with the segregation streak in the 422 billet.
20. EP 428
Russian Grade similar to AISI 422 used for steam turbine blades
100 µm
Tempered martensite structure of EP 428 martensitic
stainless steel; Vilella’s reagent.
21. CA-6NM (Casting Alloy)
Fe - <0.06%C – 12.5% Cr – 4% Ni – 0.7% Mo
10 µm
100 µm
Martensitic structure (with some delta ferrite – arrows) in cast
CA-6NM stainless steel; Ralph’s reagent.
22. AISI 440C – As Cast
Fe – 1.05% C – 17% Cr – <0.75% Mo
100 µm 20 µm
As-microstructure of 440C with a dendritic structure and carbides in the
interdendrtitic regions; Ralph’s reagent.
23. AISI 440C - Annealed
10 µm 10 µm
Annealed microstructure, ferrite and carbides, in 440C martensitic stainless
steel. Excessive cold reduction (wire drawing) will crack the larger Cr7C3
carbides (right). Villela’s reagent.
24. AISI 440C - Annealed
20 µm
Annealed 440C etched with Beraha’s CdS reagent, polarized light plus
sensitive tint.
25. FED-14 (Casting Grade)
Fe – 2.21% C – 0.92% Mn – 0.54% Si – 12.65% Cr – 0.3% Ni – 0.7% Mo – 0.11% V
100 µm 20 µm
Tempered martensite and extensive alloy carbide networks in FED-14,
670HV, Beraha’s sulfamic acid reagent No. 4.
26. FED-18 (Casting Grade)
Fe – 3.1% C – 0.75% Mn – 1.03% Si – 18.59% Cr – 0.22% Ni – 1.96% Mo
20 µm
100 µm
Tempered martensite and extensive alloy carbide networks in FED-84,
657HV, Beraha’s sulfamic acid reagent No. 4.
27. FED-25 (Casting Grade)
Fe – 2.84% C – 0.67% Mn – 0.48% Si – 25.92% Cr – 0.21% Ni – 0.14% Mo
100 µm 20 µm
Tempered martensite and extensive alloy carbide networks in FED-25,
643HV, Beraha’s sulfamic acid reagent No. 4.
29. AISI 409
Fe – <0.08% C – 11.2% Cr – 0.5% Ni + Ti
Microstructure of 409 stainless steel sheet revealed using Vilella’s reagent.
30. P/M AISI 409
20 µm
50 µm
Microstructure of ferritic P/M 409 stainless steel that was not fully
compacted. Note the voids and oxides at grain boundaries and within
grains; Vilella’s reagent.
31. AISI 430F
Fe - <0.12% C – 17% Cr - >0.15% S
50 µm
Sulfide inclusions in wrought, con-cast 430F resulfurized stainless steel;
Ralph’s reagent, longitudinal plane.
32. High-Carbon 430 Stainless Steel
Fe - <0.12% C – 17% Cr
100 µm 20 µm
To obtain high strength, Carpenter makes a high-carbon (within the
specification range) version of 430 stainless steel, quenched and tempered,
producing ferrite and martensite (modified Fry’s reagent).
34. Monit®
Fe - <0.025% C – 25% Cr – 4% Ni – 4% Mo - <0.035N + Nb/Ta
Ferritic grain structure of Monit, 60% HNO3 in water, 1 V dc, 60 s.
50 µm
35. Sea-Cure®
Fe - <0.025% C – 27.5% Cr – 1.2% Ni – 2.5% Mo - <0.025% N – 0.5% Ti
Ferritic grain structure of annealed Sea-Cure ferritic stainless steel
etched with 60% HNO3, 1.5 V dc, 2 minutes.
36. E-Brite® (26Cr-1Mo)
Fe - <0.015% C – 26.25% Cr – 1.2% Mo - <0.015% N
100 µm
Bi-modal grain-size distribution (longitudinal plane) in 26Cr-1Mo ferritic
stainless steel (60% nitric acid in water, 1 V dc, 20 s).
37. 29-4 Ferritic Stainless Steel
Fe - <0.010% C – 29% Cr – 3.8% Mo - <0.02% N
100 µm
Microstructure of a weld in 29-4 ferritic stainless steel;
60% HNO3, 1.5 V dc.
38. 29-4-2 Ferritic Stainless Steel
Fe - <0.010% C – 29% Cr – 2.25% Ni – 3.7% Mo - <0.020% N
100 µm
Ferritic grain structure of 29-4-2 stainless; etched with 60%
HNO3, 1.5 V dc, 90 s.
40. AISI 203
Fe - <0.08% C – 5.75% Mn – 17% Cr – 5.75% Ni – 2% Cu - <2% Mo – 0.25% S
50 µm 20 µm
Manganese sulfides in 203 stainless (left: as-polished); grain structure and
delta ferrite (right: Ralph’s reagent).
41. AISI 203
20 µm
Martensite produced in cold worked 203 stainless steel
containing some delta ferrite stringers and manganese
sulfides (longitudinal plane); Ralph’s reagent.
42. AISI 301 – As Cast
Fe – <0.15% C – 17% Cr – 7% Ni
100 µm 100 µm
Nomarski DIC
Bright Field
As-cast dendritic structure of type 301 austenitic stainless steel.
Ralph’s reagent.
43. Custom Flo 302-HQ
Fe - <0.08% C - <2% Mn – 18% Cr – 9% Ni – 3.5% Cu
200 µm
Austenitic grain structure of solution annealed, wrought Custom Flo 302-HQ stainless steel
tint etched with Beraha’s BII reagent and viewed with polarized light plus sensitive tint.
44. Custom Flo 302-HQ
20 µm
Delta ferrite stringer in 302 revealed using
waterless Kalling’s reagent.
46. AISI 303
Fe - <0.15% C – 18% Cr – 9% Ni – 0.6% Mo - >0.15% S
20 µm
20 µm
Manganese sulfides (left) and manganese selenides (right) in 303 and
303-Se stainless steel (as-polished).
47. AISI 303
20 µm
Austenitic grains and manganese sulfides in type 303 stainless steel;
Ralph’s reagent (does not attack sulfides).
48. AISI 303
10 µm 20 µm
Martensite produced by cold working type 303 stainless (different
specimens) revealed by Ralph’s reagent (left) and waterless
Kalling’s reagent (right).
50. AISI 304
Fe - <0.08% C - <2% Mn - <1% Si – 19% Cr – 9.25% Ni
Microstructure of solution annealed type 304 stainless steel revealing austenite grains
containing annealing twins. Etched with Kalling’s No. 2 reagent (“waterless” Kalling’s).
Original at 100X.
51. AISI 304 – Cold Drawn
Microstructure of cold drawn 304 stainless steel showing stress-induced martensite; left –
bright field; right – Nomarski DIC (15 mL HCl – 10 mL acetic acid – 10 mL HNO3)
Bright Field Nomarski DIC
52. AISI 304
50 µm 10 µm
Stress-induced martensite (arrows) in cold worked 304 stainless steel
revealed by etching with Vilella’s reagent.
53. 304 Stainless, Cold Drawn 18%, Solution
Annealed and Sensitized
100 µm
100 µm
Grain structure of sensitized 304 revealed by etching with (left) 10% oxalic
acid electrolytic and (right) with 10% ammonium persulfate, both at 6 V dc.
10% Oxalic Acid, 6 V dc 10% Ammonium persulfate, 6 V dc
54. AISI 304 - Sensitized
100 µm
Carbides were precipitated on the austenite grain boundaries of this specimen of type 304
austenitic stainless steel that was solution annealed (1038 °C – 1 h, water quench) and aged
at 650 °C for 2 h. Precipitation on twin boundaries is in a much lesser amount. The
carbide was darkened by etching with aqueous 10% ammonium persulfate, 6 V dc, 10 s.
55. 316L Solution Annealed at 1750 °F
Fe - <0.03% C – 17% Cr – 12% Ni – 2.5% Mo
50 µm
50 µm
Grain structure of 316L revealed using (left) waterless Kalling’s and (right)
with 60% HNO3 in water, 1.5 V dc, 2 minutes, Pt cathode.
Kalling’s No. 2 60% HNO3, 1.5 V dc, 120 s
56. 316L Solution Annealed at 1750 °F
Austenitic grain structure and delta ferrite stringer revealed using
Beraha’s BI tint etch.
57. AISI 316L
200 µm
Austenitic grain structure of type 316L stainless steel that was cold reduced 30% in
thickness and solution annealed at 1150 °C. Tint etched with Beraha’s BII reagent
and viewed with polarized light plus sensitive tint.
58. 316L Solution Annealed at 1750 °F
20% NaOH, 3 V dc, 10 s NH4OH, 5 V dc, 10 s
Delta ferrite (left) and carbides (right) found along the centerline of this
316L stainless steel bar.
59. AISI 316 – As Cast
Fe - <0.08% C – 17% Cr – 12% Ni – 2.5% Mo
100 µm 20 µm
As-cast microstructure of 316 stainless contains more delta ferrite than
seen after hot working due to segregation during solidification.
Glyceregia etch.
60. AISI 316
100 µm 100 µm
Acetic Glyceregia Marble’s Reagent
Revealing the austenitic grain structure of 316 stainless
steel with different etchants.
61. AISI 316
100 µm 100 µm
HCl – HNO3 – H2O 10% Oxalic Acid, 6 V dc, 10 s
Revealing the austenitic grain structure of 316 stainless steel with
different etchants.
62. AISI 316
100 µm
60% HNO3 in H2O, 0.6 V dc, 90 s
Revealing the austenitic grain structure of 316 stainless steel
with different etchants.
63. AISI 316
Microstructure of solution annealed type 316 stainless steel revealing
austenite grains containing annealing twins. Tint etched with Beraha’s
solution (15 mL HCl – 85 mL water – 1 g K2S2O5).
64. AISI 316
Microstructure of solution annealed type 316 stainless steel
revealing austenite grains containing annealing twins. Etched
with Kalling’s No. 2 reagent (“waterless” Kalling’s).
65. AISI 316 - Sensitized
100 µm
316 stainless steel sensitized by aging at 1200 ºF for 2 h to precipitate
Cr23C6 carbide on the grain boundaries. Etched with equal parts of
HNO3, HCl and water.
66. AISI 316
AISI 316 stainless steel solution annealed at 1093 ºC and etched with 60%
HNO3 in water at 1.5 V dc for 2 minutes which reveals nearly all of the
grain boundaries and very little of the twin boundaries.
67. As-Cast CF-8 M
Fe - <0.08% C – 19.5% Cr – 10.5% Ni – 2.5% Mo
50 µm 50 µm
As-Cast As-cast and Solution Annealed
Delta ferrite in as-cast and as-cast and solution annealed CF-8M
stainless steel revealed using glyceregia.
68. AISI 321
Fe - <0.08% C – 18% Cr – 10.5% Ni + Ti
Bright Field Nomarski DIC
Delta ferrite stringers in an austenitic matrix (longitudinal plane) is solution annealed
321 stainless steel; left – bright field; right – Nomarski DIC (etched with 15 mL HCl –
10 mL acetic acid – 10 mL HNO3).
69. AISI 347
Fe - <0.08% C – 18% Cr – 11% Ni + Nb
100 µm 100 µm
5% Reduction 10% Reduction
Effect of cold reduction in diameter on the austenitic grain structure
and slip deformation revealed using 60% HNO3 at 4 V dc.
70. AISI 347
100 µm 100 µm
30% Reduction
15% Reduction
Effect of cold reduction in diameter on the austenitic grain structure and
slip deformation revealed using 60% HNO3 at 4 V dc.
71. AISI 347 – 15% Cold Reduction
50 µm
100 µm
Grain structure and slip revealed by electrolytic etching with 60% HNO3,
1.4 V dc, 60 s.
72. 22-13-5 (Nitronic 50)
Fe - <0.06% C – 5% Mn – 22% Cr – 12.5% Ni – 2.25% Mo – 0.2% Nb – 0.2% V – 0.3% N
100 µm
Duplex grain size distribution in solution annealed 22-13-5 austenitic stainless steel
etched with “waterless” Kalling’s reagent.
73. SCF-19
Fe – 0.03% C – 5% Mn – 20% Cr – 18% Ni – 5% Mo – 0.35% N
100 µm
Necklace-type duplex grain size distribution in SCF-19 austenitic stainless steel that was cold reduced
10% in thickness and solution annealed at a low temperature (900 °C – 1 h, water quench). Etched
with aqueous 60% HNO3, 1 V dc, 60 s. Complete recrystallization, and grain growth, would occur at
a higher temperature, 1180 °C is the recommended solution annealing temperature.
74. 18-18 Plus
Fe - <0.15%C – 18% Mn – 18% Cr – 1% Mo – 1% Cu – 0.5% N
50 µm
100 µm
Austenitic grain structure of 18-18 Plus, nitrogen-strengthened austenitic
stainless steel etched with Beraha’s BI reagent and viewed with polarized
light and sensitive tint.
76. AM 350
Fe – 0.09% C – 0.85% Mn – 16.5% Cr – 4.5% Ni – 2.85% Mo – 0.1% N
Microstructure of AM 350 precipitation hardening stainless steel in the solution annealed
condition revealing delta ferrite stringers (hot working axis is horizontal). Etched with
aqueous 20% NaOH at 3 V dc, 5 sec. to color the delta ferrite (martensitic matrix).
77. AM 350
50 µm 20 µm
Delta ferrite stringers in a martensitic matrix in AM 350 revealed using
modified Fry’s reagent.
78. AM 350
10 µm
Delta ferrite grains in a martensitic matrix observed on a transverse
plane in AM 350; modified Fry’s reagent.
79. AM 355
Fe – 0.12% C – 15.5% Cr 4.5% Ni – 2.9% Mo – 0.1% N
25 µm
Reverted austenite in a segregation streak in AM 355 (longitudinal
plane) revealed using glyceregia.
80. 15-5PH
Fe - <0.07% C – 14.7% Cr – 4.5% Ni – 3.5% Cu – 0.3% Nb
100 µm
Delta ferrite darkened using Murakami’s reagent (100 °C – 2 minutes)
in an 8-inch rcs billet of 15-5PH (near surface on a transverse plane).
81. 15-5PH
100 µm 25 µm
1900 °F – OQ – 900 °F – 1 h, AC 1900 °F – OQ – 925 °F – 4 h, AC
Martensitic matrix of 15-5PH (delta ferrite stringer present at right)
revealed using Vilella’s reagent (left) and modified Fry’s reagent (right).
82. 15-7Mo
Fe - <0.09% C – 15% Cr – 7% Ni – 2.5% Mo – 1.2% Al
10 µm 10 µm
Examples of delta ferrite stringers in a martensitic matrix
(longitudinal plane) in 15-7Mo (note voids and cracks associated
with the nitrides at left); waterless Kalling’s reagent.
83. 17-4 PH
Fe - <0.07% C – 16.5% Cr – 4% Ni – 4% Cu – 0.3% Nb+Ta
20 µm
20 µm
Marble’s Reagent
Modified Fry’s Reagent
Revealing the martensitic matrix and delta ferrite in 17-4PH stainless steel
with different etchants.
84. 17-4 PH
20 µm
10 N KOH, 2.5 V dc, 10 s
20% NaOH, 20 V dc, 20 s
Selective etching of delta ferrite in 17-4PH stainless
steel by electrolytic etching.
89. 17-4PH - Ferrite
Delta ferrite in 17-4PH revealed by etching with Murakami’s reagent
at 100 °C (200X).
90. 17-7PH
Fe - <0.09% C – 17% Cr – 7.1% Ni – 1.25% Al
25 µm 10 µm
Nitrides (left, as-polished) and delta ferrite stringers (longitudinal
plane) in a martensitic matrix of solution annealed and aged 17-7PH;
modified Fry’s reagent.
91. PH13-8 Mo
Fe - <0.05% C – 12.75% Cr – 8% Ni – 2.25% Mo – 1.15% Al - <0.01% N
20 µm
Tempered martensite in a fracture toughness test specimen (96.8 ksi in
plane-strain fracture toughness) etched with modified Fry’s reagent.
92. PH 13-8 Mo
Microstructure of solution annealed and aged PH 13-8 Mo precipitation hardened stainless
steel revealing a fully martensitic matrix. Etched with Vilella’s reagent. Original at 500X.
93. PH 13-8 Mo
Microstructure of solution annealed and aged PH 13-8 Mo precipitation hardened
stainless steel revealing a fully martensitic matrix. Tint etched with Beraha’s reagent (20
mL HCl – 80 mL water – 2 g NH4FHF – 1 g K2S2O5). Original at 1000X.
94. Custom 450
Fe - <0.05% C – 15% Cr – 6% Ni – 0.75% Mo – 1.5% Cu + Nb/Ta
25 µm
H850
Martensitic matrix of Custom 450 PH stainless steel, H850 condition;
Ralph’s reagent.
97. Custom 455
Fe - <0.05% C – 11.75% Cr – 8.5% Ni – 1.2% Ti 2% Cu – 0.3% Nb+Ta
10 µm 10 µm
H850 H900
Martensitic matrix of Custom 455 in the H850 (left) and H900 (right)
condition; modified Fry’s reagent.
98. Custom 455
50 µm 25 µm
1525 °F – AC, 1100 °F – 4 h, AC
H1100
1525 °F – WQ, 950 °F – 4 h, AC
H950
Martensitic matrix of Custom 455 in the H950 (left) and H1100 (right)
conditions; Ralph’s reagent.
100. AISI 329 (7-Mo)
Fe - <0.1% C - <2% Mn - <1% Si – 27.5% Cr – 4.5% Ni – 1.5% Mo
Bright Field Nomarski Differential Interference
Contrast
Microstructure of 7-Mo Duplex Stainless Steel (type 329) in the solution annealed
condition. Etched with aqueous 20% NaOH (3 V dc, 10 sec). Originals at 200X. Ferrite
is colored and austenite is unaffected. DIC shows very little surface relief and no
residual surface damage.
101. AISI 329 (7-Mo)
Microstructure of 7-Mo Duplex Stainless Steel (type 329) in the solution annealed condition.
Etched with LB1 (100 mL water – 20 g NH4FHF – 0.5g K2S2O5). Original at 1000X. LB1
colors the austenite (note the annealing twins), but not carbides and ferrite.
102. 7-Mo PLUS
Fe - <0.03% C – 27.5% Cr – 4.5% Ni – 1.5% Mo – 0.25% N
50 µm 50 µm
15% HCl in Ethanol 10% CrO3, 6 V dc, 10 s
Ferrite-austenite grain structure of hot-rolled and annealed 7-Mo PLUS
duplex stainless steel revealed using (left) 15% HCl in ethanol and (right)
10% CrO3 in water, 6 V dc, 10 s.
103. 7-Mo Plus
50 µm
20% NaOH, 3 V dc, 10 s
Ferrite in 7-Mo PLUS colored using aqueous 20% NaOH, 3 V dc, 10 s.
104. 7-Mo PLUS
Microstructure of 7-Mo PLUS duplex stainless steel etched with Beraha’s
reagent (15 mL HCl – 85 mL water – 1 g K2S2O5). Original at 200X. Ferrite is
colored and austenite is unaffected.
105. 7-Mo PLUS
Microstructure of 7-Mo PLUS duplex stainless steel etched with aqueous 20% NaOH (3 V
dc, 5 secs which colors the ferritic matrix blue and the austenitic particles a light yellow
(normally not colored). Hot working direction is vertical. Austenite: 362 HK; ferrite: 264
HK hardness. Original at 500X.
106. 2205
Fe - <0.03% C - <0.8% Mn – 22% Cr – 5.25% Ni – 3% Mo – 0.15% N
Microstructure of 2205 duplex stainless steel in the solution annealed condition. Etched
with aqueous 20% NaOH, 3 V dc, 12 sec. To color the ferrite. Austenite is white.
107. 2205
Ferrite colored in 2205 solution annealed at 1200 ºC revealed using 20%
NaOH, 3 V dc, 10 s.
108. CD-4MCu
Fe - <0.04% C – 25.8% Cr – 5.4% Ni – 2% Mo – 3% Cu
200 µm 100 µm
Duplex structure of cast CD-4MCu stainless steel (295 HV); waterless
Kalling’s reagent.
109. As-Cast ASTM A 890-5A
Fe – <0.03% C - <1.5% Mn - <1% Si – 25% Cr – 7% Ni – 4.5% Mo – 0.2% N
Microstructure of as-cast ASTM A 890-5A duplex stainless steel in the solution annealed
condition. Etched with aqueous 20% NaOH (3 V dc, 10 sec). Original at 100X. Ferrite is
colored and austenite is unaffected.
110. As-Cast ASTM A 890-5A
Microstructure of as-cast ASTM A 890-5A duplex stainless steel in the solution annealed
condition. Etched with Murakami’s reagent (80 °C). Original at 100X. Ferrite is colored
and austenite is unaffected.
111. As-Cast ASTM A 890-5A
Microstructure of as-cast ASTM A 890-5A duplex stainless steel in the solution annealed
condition. Etched with LB1 (100 mL water – 20 g NH4FHF – 0.5g K2S2O5). Original at
100X. Austenite is colored and ferrite is unaffected. Because it is as-cast, the are no
annealing twins in the austenite.
112. ASTM A 890 Grade 5A
200 µm 200 µm
100 mL H2O – 10g NaOH – 10g K3Fe(CN)6 – 90s 100 mL H2O – 20g NaOH – 20g K3Fe(CN)6 – 50s
Influence of etch composition on etch time at 100 °C with standard
Murakami’s (left) and modified Murakami’s (right) to reveal the ferrite phase.
113. ASTM A 890 Grade 5A
200 µm
100 mL H2O – 30g NaOH – 30g K3Fe(CN)6 – 10s
Etching for only 10 s at 100 °C with this version of modified Murakami’s
reagent colored the ferrite in only 10 s.
114. As-Cast ASTM A 890-4A
Fe - <0.03% C – 22.25% Cr – 5.5% Ni – 3% Mo – <1% Cu – 0.2% N
100 µm 100 µm
20% NaOH, 3 V dc, 10s Murakami’s, boiling
Ferrite colored in ASTM A 890-4A using (left) 20% NaOH, 3 V dc, 10 s and
(right) with Murakami’s, 90-100 °C, 120 s.
115. As-Cast CD3MN
Fe - <0.03% C – 22.25% Cr – 5.5% Ni – 3% Mo – 0.2% N
As-cast CD3MN duplex stainless steel aged 30 days at 800 °C after etching with
Murakami’s reagent for 40 s at 90 °C to color the ferrite tan. Austenite is white. The
intermetallic phases are sigma and chi phases.
117. AISI 312 Weld Metal
Fe – 0.1% C – 1.3% Mn – 0.6% Si – 29% Cr – 9% Ni
Room Temperature - Carbides 100 °C – 3 minutes – Delta Ferrite
Murakami’s reagent reveals carbides (left) when used at room
temperature and delta ferrite (right) when used at 80 – 100 °C.
118. AISI 312
Sigma phase formed in a type 312 stainless steel weld (from the delta ferrite phase) by aging
at 816 °C for 160 h. Sigma was colored green and orange by etching with Murakami’s
reagent (10 g sodium hydroxide, 10 g potassium ferricyanide, 100 mL water) for 60 s at 80
°C. The magnification bar is 20 µm in length.
119. 7-Mo PLUS
Fe - <0.1% C – 27.5% Cr – 4.5% Ni – 1.5% Mo
10 µm
Microstructure of wrought 7-Mo duplex stainless steel solution annealed and aged 48 h at
816 °C to form sigma. Electrolytic etching with aqueous 20% NaOH (3 V dc, 10 s) revealed
the ferrite as tan, the sigma orange, while the austenite was not colored. The arrows point
to new austenite produced as ferrite is consumed forming sigma.
120. SCF-23
Fe – 0.02% C –4.27% Mn – 22.43% Cr – 17.78% Ni – 5.54% Mo – 0.40% N
20 µm 10 µm
Chi phase formed in solution annealed SCF-23 aged at 1800 ºF for 24 h;
etched in 15 mL HCl – 10 mL HNO3 – 10 mL acetic acid.
121. SCF-23
20 µm
Microstructure of SCF-23 stainless steel in the solution annealed condition after
aging 48 h at 927 °C) forming chi phase in the grain boundaries and within the
grains. The chi particles were colored using Murakami’s reagent (10 g sodium
hydroxide, 10 g potassium ferricyanide, 100 mL water at 80 °C for 30 s).
123. P/M Neutro Sorb PLUS (304 + 2% B)
Fe - <0.08% C – 19% Cr – 13.5% Ni - <0.1% N + B to 2.25%
50 µm
As-cast microstructure of Neutro Sorb PLUS (2% B) tint etched with
Beraha’s reagent (10% HCl plus 1 g/100 mL potassium metabisulfite) to
color the austenite. The chromium boride, Cr2B, is unaffected.
124. P/M Neutro Sorb PLUS - 1.75% B
Microstructure of wrought, solution annealed P/M Neutro Sorb PLUS stainless
steel with 1.75% B showing chromium boride particles, Cr2B, in an austenitic
matrix after light etching with Kalling’s No. 2 reagent. Original at 1000X.
