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ABSTRACT
The properties of 65 G steel used in the manufacture of elements of soil-cultivating machines, strengthened by plasma quenching through the use of the UDGZ-200 serial installation, without water cooling, are studied. It is established that quenching leaves on the surface bands of the heat tints. Surface roughness varies from Ra 0.3 to Ra 2.6 as a result of hardening. When quenching a plate 30 mm thick, the cooling rates in the region of pearlite decomposition of austenite (750 … 500 °C) are in the range of 50–100 °C/s, which allows the supercooled austenite to be maintained until the martensitic transformation begins (270°C). In this case, quenching condition is provided. At temperatures below the martensitic transformation, the cooling rates slow down, which a factor is contributing to the prevention of cracking during quenching. As a result of reducing the arc movement speed from 33 to 24 and up to 14 m/h, occurs an increase in the hardening depth with the boundary of HV500 450 from 0.25 up to 0,35 and 0,50 mm and an increase in the width of the hardened strip from 9 to 11 and to 13 mm, respectively. Reducing the thickness of the plate from 30 to 10 mm is accompanied by an increase in the depth of hardening to 1.9 mm. The wear resistance of normalized 65 G steel as a result of plasma quenching by steel indenter friction (ShX-15) is increased by 4 times. When rubbing with corundum indenter, the wear resistance of the hardened steel is 15.3 times higher than in the case of friction with a steel indenter. This makes plasma hardening promising for strengthening elements of soil-cultivating machines in which wear conditions are closer to tests by a corundumindenter.