Plasma carburizing process for the low distortion of automobile gears

In a plasma carburizing process, the effect of the process gases such as propane (C3H8) and methane (CH4) on the uniformity of the carburized layer has been investigated using a newly designed plasma carburizing system which is equipped with an in situ quenching chamber. The uniformity of the carburized layer has been improved up to ∼23% using C3H8 at 930°C in comparison to the process using a conventional CH4 gas in the plasma carburizing. The distortion of the gears has been estimated by the measurement of the profile and lead errors at the teeth of the gear. The profile error has been decreased with the use of C3H8 up to ∼57% of the error which was obtained from the process using CH4 gas and the lead error has also been improved up to ∼50% using a masking block for a gear with a small module of ∼2 mm. In addition the effective case depth of plasma carburizing process has been increased up to ∼35% as compared with the case depth of a conventional gas carburizing process.