Laser thermal hardening of gear wheels manufactured from powder materials

Abstract

It is difficult to imagine modern mechanical engineering without timely and targeted improvement of technological processes, in connection with which new and enhanced traditional methods of manufacturing and processing various types of structures and parts are being developed. One of the ways to reduce the economic costs of machining gears made by traditional methods is the transition to the field of powder metallurgy - powder sintering. This paper presents the possibility of a local increase in the mechanical properties of gears made by powder sintering using laser processing. Laser processing was carried out on a robotic welding and heat strengthening complex, which includes a 6-axis industrial robot, a 2-axis welding positioner, a laser head and a 5 kV ytterbium fiber laser. The high porosity of the sintered material compared to cast billets is a factor limiting the possibility of using laser thermal hardening, as it increases the likelihood of melting the edges of the machined surfaces. The present work is aimed at solving this problem. Before carrying out the experiments, the main quality criteria were identified: “no melting” and “hardening depth”. In the course of a series of experiments on laser thermal hardening, it was possible to significantly increase the hardness of the samples (in the delivered state about 30 HRC), which after processing is in the range from 55 to 65 HRC with a depth of up to 2800 μm on gear teeth made of powder materials. However, open questions remain, which are resolved in performance testing, such as durability and wear.

Keywords

• powder metallurgy
• laser thermal hardening
• gear wheel
• hardening
• metallographic examination
• hardness
• microhardness