Abstract

This paper presents the results of an experimental study intended to compare the surface integrity of finish hard turned AISI 4340 and 52100 steels (57 Rc). Specifically, the paper addresses residual stresses, white layer formation and workpiece sub-surface plastic flow in hard turning of AISI 4340 by varying the feed rate and the tool cutting edge geometry. The results are compared with those obtained for AISI 52100 steel under identical conditions in a previous study (Thiele and Melkote, 1999a-b). In contrast to AISI 52100, no white layers were produced in AISI 4340 when cutting at low feed rates with a chamfered tool. Also, unlike AISI 52100, no clear evidence of an over-tempered layer was found in AISI 4340 steel under all conditions studied. Surface residual stresses in AISI 4340 steel were more compressive than AISI 52100 steel, whereas the magnitude and depth of the peak compressive residual stress tended to be greater for AISI 52100 steel. These observations are attributed to the different mechanical, thermal, and metallurgical responses of the two hardened steel alloys to machining, and are in part due to the significant difference in the carbon content of the two alloys.

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