OUTLOOKS IN SURFACE PLASTIC DEFORMATION USE TO DECREASE SURFACE ROUGHNESS IN ROLLING MILL PARTS STRENGTHENED WITH SVS-ELECTRODE MATERIALS

The purpose of this work consists in ensuring the required quality of micro-geometry and mechanical characteristics of a surface layer in rolling mill parts, in particular, surface roughness no more than Ra=2.5mkm and micro-hardness no less than 900 kgs/mm2. To ensure such micro-hardness in samples of 60HN steel there were applied coatings With the method of electrospark alloying with the use as an electrode synthetic hard tool materials based on titanium diboride (STIM-11) and titanium carbide (STIM-40NA) made by the method of self-propagating high-temperature synthesis. EIL-coatings made of thses materials are characterized with the thickness of 30mkm, micro-hardness up to 980 kgs/mm2, that exceeds four times micro-hardness of a non-hardened sample, and with roughness Ra=5…10mkm. To decrease roughness of EIL-coatings made of STIM materials for the first time there was used surface plastic deformation with smoothing that is a novelty of this investigation. Smoothing was carried out on a screw-cutting lathe with the aid of a flattener with TC6 tungsten-cobalt hard alloy indenter (r=6mm) at the rotational frequency n=70rev/min and at the indenter longitudinal feed S=0.05mm/rev and the smoothing force P=500N. As a result of smoothing the micro-hardness of surface layers made 990kgs/mm2, and roughness – Ra=1.6…1.8mkm. Conclusion: smoothing contributes to the decrease of surface layer roughness from 3 times (STIM-40NA) to 5.5 times (STIM-11) at the conservation of their mechanical characteristics that proves the outlook in use of such a technology for finishing parts surfaces strengthened with SVS-electrode materials by STIM method of electrospark alloying.