Properties of surfacings under contact loading

Abstract

Machine parts subject to high contact loads in operation are often repaired by surfacing, shielding the weld with CO 2.The contact fatigue strength of the material depends on the original properties of the surfacing and changes in these properties in the process of friction [1]. We investigated the changes in microhardness and second-order distortion of surfacing subjected to different cyclic contact loads.The samples were rollers (Fig. 1) of steel 20Kh surfaced with Sv-08G2S wire (GOST 2246-60) shielded with CO 2. To increase the fatigue strength the samples were subjected to chemicothermal treatment -case hardening in 20% fresh and 80% spent charcoal (GOST 2407-67) [2]. The surfaced samples were quenched in oil from 820~ and tempered at 200~ for 1 h. The thickness of the facing and the depth of case hardening were 0.6 and 1.4 mm respectively. The original microhardness before contact fatigue tests was 845 10 kg/mm 2.