Age-hardening Nitriding Gear Steel and Deep Case Nitriding Process

An age-hardening nitriding gear steel 20CrNi3Mn2Al and its deep case plasma nitriding technology are developed to meet the requirements of large heavy-duty and high-speed gears.The hardness of the material in air-cooled solid solution state is 283~332 HBW， which can ensure good machinability. After the treatment of using 520~540 ℃ variable temperature deep case plasma nitriding process，the steel can obtain high surface hardness，thin compound layer and gentle hardness gradient. The hardness is higher than 900 HV at 0.1 mm below the surface and more than 600 HV at 0.4 mm below the surface； the nitriding depth is deeper than 0.6 mm and the substrate hardness rises to 400~450 HV. It can be used to manufacture gears of heavy load，high speed and high precision， which can partially replace the carburized gears， and therefore leave out the carburizing and oil quenching process， simplify the technology and reduce the gear distortion.