Investigation of Causes for Limiting the Load-Carrying Capacity of Meshing Elements of Spiroid Gears

Abstract

Relatively recent spiroid gears have been found effective application in various environments and operation modes. In addition, there are differences in the applied materials and manufacturing technologies for spiroid gearwheels and worms. Spiroid gearwheels can be made of polyamides, sintered metallic powders, bronzes, steel and cast-iron. The worm is traditionally made of steels with thermal and chemical and thermal treatment to increase their strength and wear resistance. In turn, manufacturing differences lead to various causes of reducing the load-carrying capacity of spiroid gearwheels and worms. The paper considers several reasons of limiting the load carrying capacity of meshing elements of spiroid gears. Long-term experiments of spiroid gears revealed different types of failures for teeth of spiroid gearwheels. The main reason of fractures for plastic spiroid gears is shear. As for powder gearwheels, either shear or fracture is specific for them. However, threads of spiroid worms can also be broken suddenly. In order to determine the deviation in the structure and properties of the surface layer and core of nitro-carburized worms, metallographic investigations have been carried out. Threads of spiroid worms have been taken as samples which have been further subjected to all necessary manipulations to obtain micro-etches.