Materials Science, Vol. 38, No. 6, 2002 WEAR RESISTANCE OF MECHANICAL-PULSE TREATED 40Kh STEEL DURING ABRASIVE FRICTION AND CAVITATION H. M. Nykyforchyn, V. I. Kyryliv, A. I. Bassarab, and V. A. Voloshyn UDC 621.787: 620.176.16: 197.16 Mechanical-pulse hardening of 40Kh steel by frictional contact of the working surface with a special tool in various technological environments substantially increases its resistance to cavitation-erosion fracture and oil-abrasive friction wear. Treatment in the technological environment for combined alloying by carbon and nitrogen is more effective when the action of force factors weakens and the corrosion effect increases. Mechanical-pulse hardening in the environment for carbonation ensures greater depth of the hardened layer and, therefore, is more promising in application to heavily loaded components. The components of machines and mechanisms are often exploited under conditions of simultaneous abrasive and cavitation wear. These are, in particular, components of oil-production (valve disks and saddles, pistons and cylinders of drilling pumps, protective collars of swivels) and mineral-production (pistons, disks, and saddles of repumping stations) equipment. Therefore, highly effective methods for surface hardening are required. The method of mechanical-pulse treatment developed at the Physicomechanical Institute of the Ukrainian Academy of Sciences [1] ensures high hardness of the treated surface and is especially effective for increasing the resistance of structural steels against wear under the given conditions. It is realized by high-speed friction between a component and a special tool and by infusion of the cooling technological environment in the contact zone. As a result, pulse heating, cooling, and multiple shear deformations harden the surface. The use of mechanical-pulse treatment is restricted to hardening of flat surfaces and surfaces of bodies of revolution. Moreover, by a special choice of the composition of the technological environment, one can saturate the surface layers by certain chemical elements and strengthen its effect by surface alloying [2]. Since hardening of material often adversely influences its resistance to corrosion-mechanical fracture, there arises the question about the practicability of application of mechanical-pulse treatment for increasing the durability of components subject to both friction-abrasive wear and cavitation action. Therefore, the friction-abrasive and cavitation-erosion resistance of 40Kh normalized steel after mechan- ical-pulse treatment with surface alloying was compared to its wear resistance after hardening with tempering at 200°C. Method of Investigations The surface of the steel in the as-delivered condition was treated by using the research-commercial device developed at the Physicomechanical Institute on the basis of the screw-cutting lathe 1K62 on the spindle of which a hardening tool was installed with an individual drive [3]. From outside, mechanical-pulse treatment resembles the polishing procedure. Two schemes of treatment were used. According to the first one, the surfaces of rings serving as specimens for testing for wear resistance were hardened at a special mandrel. According to the second scheme, six specimens with working end surfaces were simultaneously hardened (see Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, Lviv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 38, No. 6, pp. 88 – 92, November – December, 2002. Original article submitted July 18, 2001. 1068–820X/02/3806–0873 $27.00 © 2002 Plenum Publishing Corporation 873