齿轮钢高温渗碳后的疲劳性能

Fatigue Properties of Gear Steels After High Temperature Carburizing

利用旋转弯曲疲劳试验方法,研究了Nb和Ti微合金化20CrMn齿轮钢(20CrMnNb钢:w(Nb)0.077%;20CrMnTiNb钢:w(Nb)0.048%+w(Ti)0.038%)经1 000℃高温渗碳后的疲劳性能。结果表明,Nb-Ti复合微合金化的20CrMnTiNb钢中析出相尺寸小、数量多,其渗碳层原奥氏体晶粒平均尺寸明显低于Nb微合金化的20CrMnNb钢,因而20CrMnTiNb钢的疲劳极限高于20CrMnNb钢。疲劳断口观察发现,20CrMnNb和20CrMnTiNb钢主要以近表面基体方式起裂,渗碳层中疲劳裂纹沿晶界扩展,因而晶粒尺寸较细的20CrMnTiNb钢的疲劳性能较高。

The fatigue properties of microalloying gear steels with Nb and Ti（steel A1：w（Nb）0.077%;steel A2：w（Nb）0.048%＋w（Ti）0.038%） after carburized at 1 000 ℃ were investigated by means of rotating bending fatigue tests.The results show that the precipitates in steel A2 microalloyed with Nb and Ti are smaller in size and higher in volume fraction than those in steel A1 microalloyed only with Nb resulting in the higher fatigue limit for steel A2 compared with steel A1.The SEM observation of fracture surface show that the fatigue crack initiates from the near surface matrix for both steels,and it propagates around grain boundaries in the carburized case,and thus superior fatigue properties are found for steel A2 with finer and more uniform prior austenite grains in carburized case layers.