Abstract
Observations were made on the fatigue fracture surfaces of low alloy steels, high carbon steels and also some other alloys, using a fatigue tester of the rotating beam type and employing the electron microfractograpic technique. The results obtained are as follows:
(1) The fatigue fracture surfaces of low alloy steels quenched and tempered, were classified into five types as in the case of low carbon steels, as reported in the author’s 1st report.
(2) The fracture surfaces of hardened carbon steels (0.6% carbon) did not show the characteristics of a typical fatigue fracture, but a river pattern was observed which ordinarily appears on a brittle fracture surface.
(3) In the case of high carbon steels in an annealed state the patterns observed were of a lamellar pearlite like structure on the fatigue fracture surface. The surfaces, however, had not been treated with any etchant. Parts corresponding to ferrite had the structure of fine stripes spaced at less than 200 Å, while parts corresponding to cementite were smooth and flat without any signs of a pattern of stripes.
(4) The parallel patterns were observed principally on the fatigue fracture surfaces of 13% Cr steel, 18-8 austenitic steel and 6-4 brass.
