Chemical heat treatment of carburized helical gear wheels

Previously abstracted from original as item 9110-56-1190. Equipment with carbon potential control was used to gas carburize spiral gear teeth made of 20Kh3MVFA, 18Kh2N4MA, and 20Kh2N4A steels to optimize the C content in the carburized layer. The gas used was an endogas mixture with 7-10% natural gas and additions of ammonia and other compounds. Stepped control of the natural gas level, with decreased amounts in the later stages of carburizing, and die quenching after carburization made it possible to achieve carburized coatings with the required properties. Bend strength increased with increased tempering temperatures in the range 120-170 deg C for 20Kh2N4A and 18Kh2N4MA steels. The above recommendations should help to prevent the formation of cracks during the finish grinding of these gear teeth.