WEAR RESISTANCE OF LAYERS ON 5KHNM GRADE STEEL OBTAINED BY POWDER BOROMEDNING

The wear resistance of structural steels has a great impact on technology and economics in mechanical engineering. One of the most expensive production bases are stamps, which operate in difficult conditions and are subject to wear. The development of methods for strengthening their surfaces, which reduce wear and thereby increase the life of stamps, is a very important direction both from the point of view of their manufacturing technology and from the point of view of cost savings due to an increase in the life cycle of production equipment. Currently, 5KHNM grade steel is used primarily for the manufacture of die tooling in large-scale production. The technology of the process of chemical and thermal treatment of the steel in question by boromining in order to increase the wear resistance of its surface is considered. The boromining process was carried out in a steel furnace using sealed containers in a mixture containing 62 % B4C, 17 % CuO, 19 % Al, 2 % NaF, at a temperature of 950 °C and a holding time of 4 h. The structure of the resulting reinforcing coating is needle-like. The surface hardness due to the reinforcing layer has reached 1850 HV and decreases to 1000 HV at a depth of 180 microns. A friction machine with an integral evaluation method was used to measure wear. During the process of coating wear, there is an abundant separation of small metal particles and the diffusion layer. The separated particles, falling into the zone of mechanical contact of the parts, cause micro-cutting of their surface. However, despite this, the wear resistance of coated steel increased by more than 22 times according to the results of a thirty-minute test on a friction machine. Heat treatment of steel was used as a comparative hardening technology, as a result of which its wear resistance increased only 2.6 times under the same test conditions.

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