Some Manifestations of Antioxidation Coating for Hot Precision Forging Gears

A high temperature protective coating was prepared onto the surface of 20CrMnTi steel by brushing technique, and the heated billet was subjected to hot forging. Compared with an uncoated sample, the effect of coating on higherature oxidation behavior of steel was investigated by scanning electron microscopy-energy dispersive spectroscopy and X-ray diffraction. Before hot forging, an oxide layer of 153 μm was formed on the surface of the uncoated sample; however, no oxide layer was formed on the surface of the coated sample. After hot forging, the thickness of scale on the surface of uncoated gear forging is 89 μm while the thickness of coating on the surface of coated gear forging is 39 μm. It is concluded that such a coating material not only enhances the dimensional accuracy but also improves the surface quality of the gear.