Comparison of secondary hardening embrittlement in tungsten and molybdenum steels
- PDF / 2,093,861 Bytes
- 4 Pages / 597 x 774 pts Page_size
- 56 Downloads / 221 Views
This work was supported, in part, by the Korea Science and Engineering Foundation (KOSEF) under Contract No. 881-0608-016-2. REFERENCES 1. Y. Tomita, S. Oki, and K. Okabayashi: Tetsu-to-Hagan~, 1978, vol. 64, pp. 459-68. 2. Y. Tomita, S. Oki, and K. Okabayashi: Tetsu-to-Hagan~, 1978, vol. 64, pp. 78-87, 3. S.-M. Kang and H. Kwon: Metall. Trans. A, 1987, vol. 18A, pp. 1587-92. 4. K.B. Lee and H. Kwon: Metall. Trans. A, 1988, vol. 19A, pp. 2606-11. 5. C.K. Choi and H. Kwon: Scripta Metall. Mater., 1991, vol. 25 (2), in press. 6. M.R. Plichta and H.I. Aaronson: Metall. Trans., 1974, vol. 5, pp. 2611-13. 7. J.Y. Koo and G. Thomas: Metall. Trans. A, vol. 8A, 1977, vol. 8A, pp. 525-28. 8. H. Kwon and C.H. Kim: Metall. Trans. A, 1986, vol. 17A, pp. 745-46. 9. H. Kwon and C.H. Kim: Metall. Trans. A, 1986, vol. 17A, pp. 1173-78. 10. H. Kwon and J.W. Hong: MetaU. Trans. A, 1989, vol. 20A, pp. 560-63.
METALLURGICAL TRANSACTIONS A
Comparison of Secondary Hardening Embrittlement in Tungsten and Molybdenum Steels HOON K W O N
Secondary hardening steels have been used as heatresisting alloys because they retain high hardness at elevated temperatures. After tempering in the secondary hardening temperature range, however, embrittlement generally occurs. This embrittlement is referred to as secondary hardening embrittlement (SHE). Secondary hardening embrittlement can be classified into two types, intergranular and transgranular, according to fracture mode. It has been suggested that HOON KWON, Associate Professor, is with the Department of Metallurgical Engineering, College of Engineering, Kookmin University, Seoul 136-702, Korea. Manuscript submitted May 8, 1989.
VOLUME 22A, MAY 1991- - 1119
intergranular SHE is caused by impurity segregation, resuiting in easy intergranular fracture, tl,21 and that transgranular SHE is associated with coarse boundary carbides, leading to easy transgranular fracture, t3,4,51In recent years, Kwon [6'7'8] reported that the intergranular SHE in the overaged condition, as compared to the transgranular SHE in the underaged condition, occurred for the Mo steel and the W-Ni steel. Hence, the fracture behavior in SHE can be greatly affected by aging condition. The secondary hardening due to precipitation of fine alloy carbides t9,1~ also contributes to SHE. Since the precipitation of fine alloy carbides (i.e., MozC or W2C) in the Mo and W steels leads to secondary hardening, the degree of secondary hardening is affected by the precipitation kinetics of alloy carbides, till The Mo steel exhibits strong secondary hardening, because the precipitation of fine Mo2C occurs at relatively low temperature, where the matrix can provide more sites (e.g., dislocations) for precipitation, whereas the W steel shows a weak secondary hardening, since the relatively coarse W2C particles precipitate at relatively high temperature. This difference in degree of secondary hardening for the Mo and W steels can have an important effect on SHE. The aim of this study is to compare the differences in SHE for the Mo and W ste
Data Loading...
