1.25C-1.5Cr-5Al轴承钢中合金元素扩散对κ碳化物不均匀形核的影响

Effect of Alloying Elements Diffusion on Heterogeneous Nucleation ofκ-Carbide in 1.25C-1.5Cr-5Al Bearing Steel

采用组织观察、成分检测、热力学计算及结构分析等方法研究了1.25C-1.5Cr-5Al轴承钢离异共析相变过程中Al对κ碳化物不均匀形核的影响,并验证了混合碳化物组成的粒状珠光体对该钢最终硬化热处理组织及性能的影响。结果表明:退火温度由850℃降低至800℃过程中部分未溶解渗碳体溶解入奥氏体基体,未溶解渗碳体含量(体积分数)由(3.1±0.5)vol.%降低至(2.8±0.6)vol.%。高退火温度下的高扩散速度使Al能够在奥氏体中均匀分布,θ/γ界面附近不存在Al偏聚。铁素体中的高Al含量为κ碳化物形核提供成分需求。铁素体中高浓度Al有助于κ碳化物在渗碳体表面成核。

Through microstructure observation,chemical composition detection,thermodynamic calculation and structure analysis,the effect of Al on the heterogeneous nucleation ofκ-carbide during the divorced-eutectoid transformationprocess of 1.25C-1.5Cr-5Al bearing steel is studied,and the influence of spheroidal pearlite consisting of a mixture of carbides on the final quenched treatment's microstructure and hardness of steel is investigated.The results shows that when the annealing temperature decreases from 850℃to 800℃,a small amount of undissolved cementite dissolves into austenite,and the non-dissolved cementite content(volume fraction)decreases from(3.1±0.5)vol.%to(2.8±0.6)vol.%.There is no segregation of Al in austenite along theθ/γinterface due to its high diffusion rate at high annealing temperature.Theκ-carbide nucleation at the cementiteinterface is facilitated by ferrite’s high Al concentration.