Investigation of the sulfurizing soft- nitriding process after carburizing of the steel GDL- 1

Carburizing and sulfurizing soft-nitriding composited heat treatment of the steel GDL-1 was investigated by the orthogonal experiment method.The effect of time,temperature and concentration of CNO-to the hardness,nitriding depth and compound layer depth of the steel GDL-1 were analyzed.The result is as follows: The surface hardness depend on the concentration of CNO-,with the CNO-concentration increased,the trend of the surface hardness is first rose and then dropped,the surface hardness reaches its maximum when the CNO-concentration is about 18%.The temperature and time have a great influence on the depth of the nitriding layer,with the rise of temperature and the lengthen of the time the depth of the layer increases,but when the temperature exceed 560℃ and time reaches 2.5 hours,the increase speed of the depth of the layer is slow down.The formation of the compound layer depend on the temperature,the compound layer will rapidly thickening when the temperature exceed 560℃.The best parameters is: CNO-18%,(560±10)℃×2.5 h.