Sensitization of Austenitic Stainless Steels, I. Controlled Purity Alloys

CORROSION ◽  
1982 ◽  
Vol 38 (9) ◽  
pp. 468-477 ◽  
Author(s):  
C. L. Briant ◽  
R. A. Mulford ◽  
E. L. Hall
Keyword(s):  
Carbon Content ◽  
Stainless Steels ◽  
Analytical Electron Microscopy ◽  
Austenitic Stainless Steels ◽  
Carbide Formation ◽  
Beneficial Effects ◽  
Acid Etch ◽  
Parameter Versus ◽  
Type 304 ◽  
Sensitization Time

Abstract This paper presents a study of the effects of carbon, nitrogen, molybdenum, and manganese on the sensitization of high-purity austenitic stainless steels of composition similar to Type 304. The modified Strauss test (ASTM-A262-E), the oxalic acid etch test (ASTM-A262A) and analytical electron microscopy were used to determine the degree and nature of sensitization in the steels. The alloy compositions are considered in terms of effective chromium content, and from plots of this parameter versus sensitization time a strong effect of carbon content is seen. Additions of nitrogen, molybdenum, and manganese are found to delay sensitization at any given carbon concentration. In the case of nitrogen, the amount of improvement depends on both the carbon content and the sensitization temperature. Strong evidence is presented that nitrogen acts to retard the nucleation and/or growth of carbides at grain boundaries and hence increase the time necessary for sensitization. Molybdenum appears to increase the ease with which the steel passivates; thus more chromium depletion is required before sensitization will be detected. The combination of molybdenum plus nitrogen is found to be particularly effective in retarding nucleation and/or growth of carbides; molybdenum alone does not have this effect. Only limited experimental evidence is presented concerning the role of manganese. Beneficial effects of this element are primarily seen at low sensitizing temperatures, where manganese assists nitrogen in slowing carbide formation.

The Effect of Boron on the Corrosion Resistance of Austenitic Stainless Steels

CORROSION ◽  
1977 ◽  
Vol 33 (11) ◽  
pp. 408-417 ◽  
Author(s):  
F. P. A. ROBINSON ◽  
W. G. SCURR
Keyword(s):  
Corrosion Resistance ◽  
Stainless Steels ◽  
Intergranular Corrosion ◽  
Detrimental Effect ◽  
Austenitic Stainless Steels ◽  
The Other ◽  
Beneficial Effects ◽  
Identical Series ◽  
Type 304 ◽  
Intergranular Corrosion Resistance

Abstract Two Type 304 stainless steels, one boron free and the other containing 4 ppm boron were investigated. Both steels were subjected to an identical series of corrosion tests and the results compared with one another. It was found (1) Boron had no detrimental effect on the potentiostatic characteristics, intergranular corrosion “resistance and pitting resistance of the steels in the “as-received” condition; (2) boron in solid solution had no detrimental effect on the potentiostatic characteristics and intergranular corrosion resistance of the steel, while boron in solution had a beneficial effect on the pitting resistance of the steel, and (3) boron retarded Cr23C6 precipitation and thus boron had marked beneficial effects on the intergranular corrosion resistance of the steels in a sensitized condition. In addition the potentiostatic characteristics and pitting resistance of such steels were improved slightly by the presence of boron.

The Application of Analytical Electron Microscopy to Improving the Sensitization Resistance of Type 304 Stainless Steels

1985 ◽  
Vol 62 ◽  
Author(s):  
H. S. Betrabet ◽  
W. A. T. Clark
Keyword(s):  
Electron Microscopy ◽  
Stainless Steels ◽  
Volume Diffusion ◽  
Discontinuous Precipitation ◽  
Analytical Electron Microscopy ◽  
Austenitic Stainless Steels ◽  
Analytical Electron ◽  
Type 304 ◽  
Kinetics Of ◽  
Apparent Conflict

ABSTRACTThe sensitization resistance of austenitic stainless steels can be improved by replacing some of the C with N. Electrochemical potentionkinetic reactivation (EPR) tests indicate that this is effective up to ∼0.16 wt.%N, but that above this level sensitization is enhanced. Thermodynamic calculations indicate that N should continue to reduce sensitization up to at least 0.25 wt.%N, as it retards the growth kinetics of Cr carbides. Analytical electron microscopy was used to investigate this apparent conflict and showed that, while N did decrease the volume diffusion coefficient of Cr beyond 0.16 wt.%, an increase in the amount of discontinuous precipitation of carbides with increasing N was responsible for the sensitization at higher N levels.

Strain-induced martensite effects on transgranular carbide precipitation in type 304 stainless steels

1991 ◽  
Vol 49 ◽  
pp. 604-605
Author(s):  
A.H. Advani ◽  
L.E. Murr ◽  
D. Matlock
Keyword(s):  
Heat Treatment ◽  
Grain Boundary ◽  
Stress Corrosion Cracking ◽  
Stainless Steels ◽  
Deformation Twin ◽  
Austenitic Stainless Steels ◽  
Carbide Precipitation ◽  
Strain Induced Martensite ◽  
Type 304

Thermomechanically induced strain is a key variable producing accelerated carbide precipitation, sensitization and stress corrosion cracking in austenitic stainless steels (SS). Recent work has indicated that higher levels of strain (above 20%) also produce transgranular (TG) carbide precipitation and corrosion simultaneous with the grain boundary phenomenon in 316 SS. Transgranular precipitates were noted to form primarily on deformation twin-fault planes and their intersections in 316 SS.Briant has indicated that TG precipitation in 316 SS is significantly different from 304 SS due to the formation of strain-induced martensite on 304 SS, though an understanding of the role of martensite on the process has not been developed. This study is concerned with evaluating the effects of strain and strain-induced martensite on TG carbide precipitation in 304 SS. The study was performed on samples of a 0.051%C-304 SS deformed to 33% followed by heat treatment at 670°C for 1 h.

CARPENTER STAINLESS 304+B

Alloy Digest ◽  
1961 ◽  
Vol 10 (9) ◽  
Keyword(s):  
Fracture Toughness ◽  
Cross Section ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Heat Treating ◽  
Neutron Absorption ◽  
Absorption Cross ◽  
Type 304 ◽  
Conventional Type ◽  
Neutron Absorption Cross Section

Abstract Carpenter Stainless 304+B is similar to conventional Type 304 with the addition of boron to give it a much higher thermal neutron absorption cross-section than other austenitic stainless steels. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SS-121. Producer or source: Carpenter.

Effect of Strain-Induced Martensitic Transformation on Coaxing Effect of Austenitic Stainless Steels

2008 ◽  
Vol 385-387 ◽  
pp. 505-508
Author(s):  
Jae Woong Jung ◽  
Masaki Nakajima ◽  
Yoshihiko Uematsu ◽  
Keiro Tokaji ◽  
Masayuki Akita
Keyword(s):  
Martensitic Transformation ◽  
Stainless Steels ◽  
Work Hardening ◽  
Strain Aging ◽  
Austenitic Stainless Steels ◽  
Fatigue Tests ◽  
The Other ◽  
Conventional Tests ◽  
Materials Used ◽  
Type 304

The effects of martensitic transformation on the coaxing behavior were studied in austenitic stainless steels. The materials used were austenitic stainless steels, type 304 and 316. Conventional fatigue tests and stress-incremental fatigue tests were performed using specimens subjected to several tensile prestrains from 5% to 60%. Under conventional tests, the fatigue strengths of both steels increased with increasing prestrain. Under stress-incremental tests, 304 steel showed a marked coaxing effect, where the failure stress significantly increased irrespective of prestrain level. On the other hand, the coaxing effect in 316 steel decreased with increasing prestrain up to 15%, where the failure stresses were nearly the same. Above this prestrain level, the coaxing effect increased with increasing prestrain. In 304 steel, the coaxing effect is primarily dominated by work hardening at low prestrains, while the effect of strain-induced martensitic transformation increases with increasing prestrain. The coaxing effect in 316 steel is dominated by both work hardening and strain aging at low prestrains, but strain-induced martensitic transformation could play a significant role at high prestrains.

SSRT and Fatigue Crack Growth Properties of High-Strength Austenitic Stainless Steels in High-Pressure Hydrogen Gas

2014 ◽  
Author(s):  
Hisatake Itoga ◽  
Takashi Matsuo ◽  
Akihiro Orita ◽  
Hisao Matsunaga ◽  
Saburo Matsuoka ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
High Strength ◽  
Hydrogen Gas ◽  
Internal Hydrogen ◽  
Acceleration Rate ◽  
Type 304

Slow strain rate tests (SSRTs) were performed with two types of high-strength austenitic stainless steels, Types AH and BX, as well as with two types of conventional austenitic stainless steels, Types 304 and 316L. The tests used the following combinations of specimen types and test atmospheres: (i) non-charged specimens tested in air, (ii) hydrogen-charged specimens tested in air (tests for internal hydrogen), and (iii) non-charged specimens tested in hydrogen gas at pressures of 78 ∼ 115 MPa (tests for external hydrogen). Type 304 exhibited a marked reduction of ductility in the tests for both internal hydrogen and external hydrogen, whereas Types AH, BX and 316L exhibited little or no degradation. In addition, fatigue crack growth (FCG) tests for the four types of steels were also carried out in air and hydrogen gas at pressures of 100 ∼ 115 MPa. In Type 304, FCG in hydrogen gas was more than 10 times as fast as that in air, whereas the acceleration rate remained within 1.5 ∼ 3 times in Types AH, BX and 316L. It was presumed that, in Types AH and BX, a small amount of additive elements, e.g. nitrogen and niobium, increased the strength as well as the stability of the austenitic phase, which thereby led to the excellent resistance against hydrogen.

Influence of carbon content on the martensitic transformation of titanium stabilized austenitic stainless steels

2020 ◽  
Vol 108 (1-2) ◽  
pp. 345-356
Author(s):  
Juan Manuel Pardal ◽  
Sérgio Souto Maior Tavares ◽  
Mauro Teixeira Tavares ◽  
Pedro Soucasaux Pires Garcia ◽  
Javier Alejandro Carreno Velasco ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Carbon Content ◽  
Stainless Steels ◽  
Austenitic Stainless Steels

A TEM/STEM and APFIM study of nitrogen distribution in inert-gas-atomized type 304 stainless steels

1994 ◽  
Vol 52 ◽  
pp. 960-961
Author(s):  
M. Zhou ◽  
T. F. Kelly ◽  
J. E. Flinn
Keyword(s):  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Strengthening Mechanism ◽  
Austenitic Steels ◽  
Alloying Element ◽  
Atomic Size ◽  
High Toughness ◽  
Mechanical And Physical Properties ◽  
Interstitial Nitrogen ◽  
Type 304

The attraction of austenitic stainless steels lies in the combination of their mechanical and physical properties and corrosion resistance. However, a major disappointment is their relatively low strength. Over the years, continued efforts have been made to try to improve the strength of conventionally processed austenitic steels without sacrificing other properties. Using nitrogen as an alloying element can very effectively increase the strength of austenitic stainless steels while maintaining a high toughness. Improved resistance to intergranular corrosion and longer creep-to-rupture time1 werealso reported among nitrogen-containing austenitic steels. Though there is little doubt that interstitial nitrogen is responsible for the improved mechanical properties, the strengthening mechanism by nitrogen can not be explained successfully in a “conventional sense”, i.e. despite its smaller atomic size, nitrogen was found to increase the yield strength at 4K more than carbon does by a factor of about 2. One reason for the lack of understanding of nitrogen strengthening mechanism is because of thedifficulty of detecting low atomic number elements as well as possible short range order that may exist between interstitial and substitutional atoms.

Origin and Influence of Pre-Existing Segregation on Radiation-Induced Segregation In Austenitic Stainless Steels

1998 ◽  
Vol 540 ◽  
Author(s):  
E. A. Kenik ◽  
J. T. Busby ◽  
M. K. Miller ◽  
A. M. Thuvander ◽  
G. Was
Keyword(s):  
Electron Microscopy ◽  
Grain Boundaries ◽  
Stainless Steels ◽  
Analytical Electron Microscopy ◽  
Austenitic Stainless Steels ◽  
Atom Probe ◽  
Molecular Ions ◽  
Probe Field ◽  
Analytical Electron ◽  
Radiation Induced

AbstractThe pre-existing segregation at grain boundaries in two austenitic stainless steels has been investigated by atom probe field ion microscopy and analytical electron microscopy. In addition, the effect of radiation-induced segregation on the near-grain-boundary composition has been studied by analytical electron microscopy. Pre-existing enrichment of Cr, Mo, B, C and P and depletion of Fe and Ni near grain boundaries has been observed. Significant affinity between Mo and N in both alloys is indicated by the detection of MoN2+` molecular ions during field evaporation. The pre-existing segregation is modified by radiation-induced segregation resulting in Ni and Si enrichment near the boundary as well as depletion of chromium adjacent to the boundary resulting in a “W-shaped” Cr profile.

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