Hydrogen-Induced subcritical crack growth of a 12 Cr-1 Mo ferritic stainless steel
- PDF / 3,927,704 Bytes
- 12 Pages / 594 x 774 pts Page_size
- 56 Downloads / 179 Views
I.
INTRODUCTION
FERRITIC stainless steels are being considered for structural applications in fusion reactors, where hydrogen embrittlement and stress corrosion may occur. Because the integrity of the plasma chamber and structural components is an important factor in fusion reactor design, potential material degradation processes are of great concern. Segregation of impurity elements such as phosphorus and sulfur has been shown to affect the hydrogen embrittlement and intergranular corrosion of ferritic steels,~'2'3 and it is known that phosphorus and sulfur segregation can occur during heat treatment, fabrication, and service above 450 ~ Therefore, the effects of impurity segregation on the hydrogen embrittlement and stress corrosion of ferritic stainless steels must be identified. In a previous study, 4 the effect of heat treatment on grain boundary chcmistry, hydrogen embrittlement, and stress corrosion was evaluated. Auger electron spectroscopy (AES) of intergranular surfaces revealed that the grain boundary phosphorus and sulfur concentrations of the 12 Cr-I Mo ferritic stainless steel depended on heat treatment. After a tempering treatment of 2.5 hours at 760 ~ the grain boundary phosphorus and sulfur concentrations were 0.015 and 0.03 monolayers, respectively; after a heat treatment of 240 hours at 540 ~ grain boundary concentrations were 0.04 and 0.01 monolayers, respectively. Straining electrode tests at cathodic and anodic test potentials indicated that this steel is quite sensitive to hydrogen embrittlement but less susceptible to stress corrosion at 25 ~ in an acidic electrolyte. The reduction of area was 13 pct at cathodic test potentials and 60 pct in air and at anodic test potentials. This decrease in reduction of area at cathodic potentials was accompanied by an increase in quasi-cleavage and intergranular fracture. Recent studies have shown that internal 5 or external cathodic4 hydrogen induces brittle, intergranular fracture of R. H. JONES is Technical Leader, Metals Research Grbup, Metals and Ceramic Science Section, Department of Materials Science and Technology, Battelle-Northwest Laboratory, Richland, WA 99352. Manuscript submitted December 17, 1984. METALLURGICALTRANSACTIONS A
the 12 Cr-I Mo ferritic stainless steel. These studies measured only the tensile ductility; fracture threshold and crack gr~.wth rate data are needed to identify the embrittling mechanism and to determine critical flaw size. The purpose of this study was to measure the subcritical crack growth in the presence of external cathodic hydrogen at 25 ~ to relate this growth to the ductility, and to identify the important chemistry and microstructural features responsible for the susceptibility to hydrogen embrittlement.
II.
DESCRIPTION OF MATERIAL AND EXPERIMENTAL PROCEDURE
A. Material
Straining electrode and compact tension samples were taken from 13-mm-thick plate of heat 9607 from the fusion reactor materials stockpile. The chemical composition of this material is given in Table I. The sulfur and phosphorus concentr
Data Loading...
