Morphology of Stress-Corrosion Cracks In Notched Specimens of Austenitic Stainless Steels

CORROSION ◽  
1964 ◽  
Vol 20 (5) ◽  
pp. 174t-178t ◽  
Author(s):  
J. C. SCULLY ◽  
T. P. HOAR

Abstract The pattern of stress-corrosion cracking of notched specimens of an 18 Cr-8 Ni austenitic stainless steel stressed in 42 percent aqueous magnesium chloride solutions is described. It illustrates the action of both tensile and shear stresses in promoting fracture: cracks are nucleated along directions of maximum shear strain and their propagation paths are determined by these and the acting tensile stress.

CORROSION ◽  
1962 ◽  
Vol 18 (6) ◽  
pp. 230t-239t ◽  
Author(s):  
H. W. PICKERING ◽  
F. H. BECK ◽  
M. G. FONTANA

Abstract A study was made of corrosion products and their effects on stress corrosion cracking of austenitic stainless steel. Wedging action by solid corrosion products in notches or cracks induces high stresses and eventual failure of specimens by stress corrosion cracking. Data were obtained from stress-relieved and unloaded (externally) specimens so that wedging by corrosion products provided the only source of stress in the specimen. Pressures were measured in excess of 7000 psi due to wedging action of corrosion products. At the base of a notch these pressures developed stresses of the order of magnitude of the yield strength of the metal. Wedging action can provide all the energy required for stress corrosion cracking. A mechanism is proposed which involves a discontinuous type of propagation, with fluctuations occurring over one or a few atomic distances. A running or mechanical type of crack propagation for more than a few atomic distances is ruled out on the basis of the mechanics of the system. 3.4.3, 3.5.8, 6.2.5


CORROSION ◽  
1958 ◽  
Vol 14 (12) ◽  
pp. 60-64 ◽  
Author(s):  
L. R. SCHARFSTEIN ◽  
W. F. BRINDLEY

Abstract Overstressed U-bends of Types 304 and 347 stainless steels were exposed to water containing chloride ions to determine the susceptibility of these steels to stress corrosion cracking between the temperatures of 165 F and 200 F. The pH was controlled at 6.5 to 7.5 and 10.6 to 11.2 for the tests. At the high pH, cracks appeared at the edges with little evidence of pitting. At the neutral pH, cracks were found at the edges and associated with pits. Sensitized Type 304 had longer and deeper cracks than annealed Types 304 and 347 in the same exposure time. Conclusion is made that chloride stress corrosion cracking of these steels in the temperature range of 165 F to 200 F is less severe than that experienced at 500 F and that specific conditions are required for corrosion cracking to occur at all. 3.2.2


CORROSION ◽  
1964 ◽  
Vol 20 (9) ◽  
pp. 269t-274t ◽  
Author(s):  
C. R. BERGEN

Abstract The mechanism of stress corrosion crack initiation can perhaps be understood by noticing the similarities among the several corrodent-crack susceptible alloy systems. In a number of such systems the specific ion responsible for cracking is relatively large. The corrosion product formed in a corroding medium containing such ions would imbibe them. Under appropriate conditions, due to their size, the larger ions would tend to diffuse to the region of the oxide film under highest tensile stress where local high tensile stress in the base alloy would be reflected. It is postulated that the appropriate conditions for diffusion are present in stress cracking systems and that the migration of the ion to which cracking is ascribed leads to high local concentrations in turn causing a local increase in corrosivity. Where the physical properties of the alloy are such that crack propagation can occur, stress corrosion cracking results. Tests of the above hypothesis have been conducted with the chloride-austenitic stainless steel system. It was shown that chloride will migrate reversibly under the influence of tensile stress. It was also shown that the presence of nickel will inhibit the migration of chloride up a tensile gradient and the immunity to cracking of high nickel austenitic stainless alloys is attributed to this effect.


CORROSION ◽  
1969 ◽  
Vol 25 (1) ◽  
pp. 15-22 ◽  
Author(s):  
A. W. LOGINOW ◽  
J. F. BATES

Abstract In certain applications, stress corrosion cracking of austenitic stainless steels has occurred when these steels are subjected to tension stresses (residual and applied) and are exposed to hot chloride solutions. Although stress corrosion cracking can be prevented by treatments to relieve residual stresses and by control of the environment, such procedures are expensive and not always reliable. An extensive study was therefore undertaken to develop a steel that would-be inherently resistant to stress corrosion cracking. The results of the study, conducted on stressed specimens of experimental steels immersed in a boiling 42% magnesium chloride solution, showed that carbon and nickel improved the stress corrosion resistance of annealed steels, and? nickel and silicon increased the resistance of cold-worked steels. It was also found that nitrogen decreased the resistance of annealed steels whereas phosphorus and molybdenum decreased the resistance of cold-worked steels. Manganese, copper, chromium, sulfur, and aluminum had little or no effect on stress corrosion resistance. This study resulted in the formulation of a steel composition containing 18% chromium, 18% nickel, 2% silicon, and 0.06% carbon, with low phosphorus and molybdenum contents. This steel was melted in an electric furnace; and1 its, stress corrosion, corrosion, and mechanical properties were determined. Test results show that the new steel (called USS 18-18-2 stainless steel) is much more resistant to stress; corrosion cracking than currently available austenitic stainless steels. Furthermore, the resistance of this steel is better than that of a 20% chromium, 34% nickel alloy that is being marketed; for its resistance to stress corrosion cracking.


2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Alberto Sáez-Maderuelo ◽  
Dolores Gómez-Briceño ◽  
César Maffiotte

The supercritical water reactor (SCWR) is one of the Generation IV designs. The SCWR is characterized by its high efficiency, low waste production, and simple design. Despite the suitable properties of supercritical water as a coolant, its physicochemical properties change sharply with pressure and temperature in the supercritical region. For this reason, there are many doubts about how changes in these variables affect the behavior of the materials to general corrosion or to specific types of corrosion such as stress corrosion cracking (SCC). Austenitic stainless steels are candidate materials to build the SCWR due to their optimum behavior in the light water reactors (LWRs). Nevertheless, their behavior under the SCWR conditions is not well known. First, the objective of this work was to study the SCC behavior of austenitic stainless steel 316 type L in deaerated supercritical water at 400°C/25  MPa and 30 MPa and 500°C/25  MPa to determine how variations in pressure and temperature influence its behavior with regard to SCC and to make progress in the understanding of mechanisms involved in SCC processes in this environment. Second, the oxide layer formed at 400°C/30  MPa/<10  ppb O2 was analyzed to gain some insight into these processes.


1999 ◽  
Vol 5 (S2) ◽  
pp. 760-761
Author(s):  
E.A. Kenik ◽  
J.T. Busby ◽  
M.K. Miller ◽  
A.M. Thuvander ◽  
G. Was

Irradiation-assisted stress corrosion cracking (IASCC) of irradiated austenitic stainless steels has been attributed to both microchemical (radiation-induced segregation (RIS)) and microstructural (radiation hardening) effects. The flux of radiation-induced point defects to grain boundaries results in the depletion of Cr and Mo and the enrichment of Ni, Si, and P at the boundaries. Similar to the association of stress corrosion cracking with the depletion of Cr and Mo in thermally sensitized stainless steels, IASCC is attributed in part to similar depletion by RIS. However, in specific heats of irradiated stainless steel, “W-shaped” Cr profiles have been observed with localized enrichment of Cr, Mo and P at grain boundaries. It has been show that such profiles arise from pre-existing segregation associated with intermediate rate cooling from elevated temperatures. However, the exact mechanism responsible for the pre-existing segregation has not been identified.Two commercial heats of stainless steel (304CP and 316CP) were forced air cooled from elevated temperatures (∽1100°C) to produce pre-existing segregation.


Alloy Digest ◽  
2019 ◽  
Vol 68 (2) ◽  

Abstract Sandvik APM 2377 is a powder metallurgical, molybdenum-alloyed, hot isostatic pressed product that is an austenitic/ferritic duplex stainless steel with improved corrosion resistance in stress-corrosion cracking over austenitic stainless steels. This datasheet provides information on composition, physical properties, and elasticity. It also includes information on corrosion resistance as well as heat treating, machining, and joining. Filing Code: SS-1302. Producer or source: Sandvik Steel Company.


CORROSION ◽  
1961 ◽  
Vol 17 (2) ◽  
pp. 53t-54t ◽  
Author(s):  
N. D. GROVES ◽  
L R. SCHARFSTEIN ◽  
C. M. EISENBROWN

Abstract A case history is given of failures of stainless steel deaerator trays used in a deaerating feed water heater. Trays fabricated from Type 201 and Type 329 stainless steels were reported to have failed by chloride stress corrosion cracking after several months' service. The cracking of the Type 201 was very severe. It is shown that conditions in parts of the deaerating heater promote failure by chloride stress corrosion cracking and the service life of austenitic stainless steels is very short. Annealing after welding of the Type 329 trays would improve resistance to cracking. It is also suggested that Type 430 stainless steel be considered since it is not susceptible to chloride stress corrosion cracking. 6.2.5, 3.5.8, 7.6.8


Alloy Digest ◽  
1999 ◽  
Vol 48 (8) ◽  

Abstract ALZ 316 is an austenitic stainless steel with good formability, corrosion resistance, toughness, and mechanical properties. It is the basic grade of the stainless steels, containing 2 to 3% molybdenum. After the 304 series, the molybdenum-containing stainless steels are the most widely used austenitic stainless steels. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: SS-756. Producer or source: ALZ nv.


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