Comparison and selection of different surface hardening processes for planetary gearbox gears
The working conditions of planetary gear reducers vary greatly, with different requirements for surface hardness, wear resistance, toughness, accuracy, and load-bearing capacity. Therefore, in addition to traditional carburizing and quenching processes, various surface hardening processes can be adapted. In actual production, it is necessary to select the optimal one based on equipment usage scenarios, performance indicators, and production costs, in order to balance the service life of gears and production cost-effectiveness.
High frequency induction hardening is an efficient surface hardening process commonly used in industry. It relies on the eddy current generated by high-frequency current to quickly heat the surface of the gear, with a controllable heating depth stable at 0.5-2mm. After rapid cooling, the local hardening treatment of the tooth surface is completed. The core advantage of this process is its extremely high processing efficiency, with a single heating process taking only a few seconds to tens of seconds, strong production adaptability, and a small heat affected area. The deformation of the gear during heat treatment is extremely low, which can perfectly preserve the basic dimensional accuracy of the gear. The processed gear tooth surface has high hardness and excellent wear resistance, and the core matrix still maintains good toughness, which can effectively resist the impact of conventional operation. However, due to the shallow hardening characteristics, its infiltration layer thickness is insufficient to withstand high pressure, heavy load, and continuous impact conditions, and is only suitable for gear machining of medium load collaborative robots, lightweight transmission equipment, and other gear reducers.
Nitrocarburizing is a low-temperature precision hardening process, with a processing temperature controlled between 500-580 ℃. Through medium infiltration, nitrogen and carbon atoms are enriched in the surface layer of the gear, forming a dense and uniform hardened compound layer with a surface hardness of HV800-1200. The biggest highlight of this process is that the heat treatment is almost deformation free, without the need for subsequent precision machining, which can maximize the precision tolerance of the gear. At the same time, the surface structure has excellent rust and corrosion resistance. However, its hardened layer thickness is relatively thin and the bonding strength is average. The overall load-bearing capacity of the gear is far inferior to that of the carburizing and quenching process, and it cannot cope with heavy load wear conditions. It is mostly used in light load, high-precision, and corrosion-resistant scenarios, and is typically applied to clean robot reducer gears in the food and pharmaceutical industries.
Boronization treatment is a special high wear resistance hardening process that completes the infiltration of boron atoms into the surface layer at high temperatures of 800-950 ℃, generating a boride hardening layer with a hardness of up to HV1800-2500, and its wear resistance far exceeds other processes. However, the drawbacks of this process are very obvious, with extremely brittle hardened layers and poor impact resistance. It is prone to cracking and peeling under stress, and is only suitable for special niche working conditions with no impact and high wear.
Through comprehensive comparison of various processes, carburizing and quenching have a deep infiltration layer, excellent comprehensive mechanical properties, and outstanding load-bearing capacity, making them the core processes for high load joint gears in industrial robots; High frequency induction hardening is suitable for medium load general scenarios; Nitrocarburizing and boronizing are targeted to serve special scenarios of precision light load and high wear
