METHOD OF IMPROVING THE PERFORMANCE OF SMALL-MODULE GEARS MADE OF HIGH-STRENGTH CAST IRON
The aim of the research was to develop a method for reducing friction forces in the engagement of gear wheels made of high-strength cast iron of agricultural machines and mechanisms with the thermal diffusion coatings with carbide-forming elements - vanadium, chromium and manganese. Scientific novelty. The scientific novelty consists in the use of thermal diffusion hardening methods, as a result, the hardness of the contact surfaces of the gear teeth of finegrained (less than 3) cast-iron gears increases, and the running-in conditions are facilitated by an external anti-friction coating that smoothes the initial surface roughness, and the use of grooves makes it possible to further increase performance by 5-10%. Methodology. The tests were carried out on a cast-iron spur gear pair with a module equal to 4, which is the rear speed of the VAZ 2107 car. The gears were subjected to the diffusion saturation from a powder medium containing the main diffusants (vanadium, chromium and manganese) in the form of ferroalloys, aluminum oxide was an inert filler, the activating rum is ammonium chloride. Then the wheels were quenched into oil with reheating in the medium of molten vanadium oxide, which has a melting point of 6750C and is inert to the coating material. In gears hardened in this way, grooves were made on the working surfaces of the teeth at an angle of 29-310 to the side surface of the tooth, in the form of a semicircle. The grooves had a depth equal to the thickness of the diffusion layer and were less than the width of the tooth, in order to hold the antifriction material, which subsequently filled them. Gears prepared in this way were subjected to wear tests as an assembly in the gearbox. Results. Tests of cast iron wheels after thermal diffusion saturation with chromium, vanadium and manganese (without the use of grooves with anti-friction material) revealed that the wear resistance of vanadium coatings is 4-4.4 times, chromium coatings 3.5-4 times and manganese coatings 2-2.5 times higher wear resistance of hardened gears made of carburized and hardened steel 20KhGN. And the presence of grooves in thermodiffusion-hardened gear cast iron wheels, which are filled with the anti-friction material, for example, tin bronze OTS 555, by any known method, in particular, with metal brushes (rubbing) or working in tandem with a donor wheel made of anti-friction material, allows to increase the wear resistance of gears made of high-strength cast iron relative to thermo-diffusion hardened, not containing grooves by 5-10%.