Secondary carbide precipitation in an 18 wt%Cr-1 wt% Mo white iron
- 350 Downloads
High chromium (18%) white irons solidify with a substantially austenitic matrix supersaturated with chromium and carbon. The austenite is destabilized by a hightemperature heat treatment which precipitates chromium-rich secondary carbides. In the as-cast condition the eutectic M7Ca3 carbides are surrounded by a thin layer of martensite and in some instances an adjacent thicker layer of lath martensite. The initial secondary carbide precipitation occurs on sub-grain boundaries during cooling of the as-cast alloy. After a short time (0.25 h) at the destabilization temperature of 1273 K, cuboidal M23C6 precipitates within the austenite matrix with the cube-cube orientation relationship. After the normal period of 4 h at 1273 K, there is a mixture of M23C6 and M7C3 secondary carbides and the austenite is sufficiently depleted in chromium and carbon to transform substantially to martensite on cooling to room temperature.
KeywordsCarbide Chromium Heat Treatment Austenite Martensite
Unable to display preview. Download preview PDF.
- 1.D. E. DIESBURG and F. BORIK, in “Symposium Materials for the Mining Industry”, edited by R. Q. BARR (Climax Molybdenum, Vail, USA, 1974) p. 15.Google Scholar
- 2.R. B. GUNDLACH, Trans. Am. Foundryman's Soc. 82 (1974) 309.Google Scholar
- 3.W. W. CIAS, ibid. 82 (1974) 317.Google Scholar
- 7.G. L. F. POWELL and J. V. BEE, in Proceedings of the Conference on “Materials and Manufacturing in Mining and Agriculture”, Brisbane (Institute of Metals and Materials Ltd., Australasia, 1993) p. 21.Google Scholar