Nb微合金化对Cr-Co-Ni-Mo系超高强度不锈钢腐蚀疲劳性能的影响

Effect of Niobium Alloying on the Corrosion Fatigue Properties of the Cr-Co-Ni-Mo Series of Ultra-high Strength Stainless Steels

为探讨超高强度不锈钢的应力腐蚀开裂行为,采用Cr-Co-Ni-Mo系超高强度不锈钢为研究对象,利用OM、XRD、TEM等测试手段,结合腐蚀疲劳试验,研究了Nb微合金化对Cr-Co-Ni-Mo系超高强度不锈钢腐蚀疲劳性能的影响。结果表明,试验钢在3.5%NaCl溶液中具有一定的应力腐蚀敏感性,其应力腐蚀开裂机理为氢致开裂和阳极溶解的混合机制。Nb微合金化提高了钢的腐蚀疲劳性能,钢中添加0.11%的Nb后,钢的腐蚀疲劳强度由440 MPa提高至495 MPa,其主要原因是,Nb微合金化可以细化钢的晶粒尺寸,促进钢中不可逆氢陷阱NbC的析出,增加了钢中原奥氏体晶界总量、小角晶界所占比例、Σ3晶界数量、奥氏体体积分数等。

In order to investigate the stress corrosion cracking behavior of ultra-high strength stainless steel, the influence of Nb microalloying on the corrosion fatigue properties of Cr-Co-Ni-Mo series ultra-high strength stainless steel was studied by OM, XRD, TEM and other testing methods in combination with corrosion fatigue test. The results show that the steel has stress corrosion sensitivity in 3. 5% NaCl solution, and the stress corrosion cracking mechanism of the steel was a mixed mechanism involving hydrogen embrittlement and anodic dissolution. Niobium alloying improved the corrosion fatigue performance of the steel, that is, the corrosion fatigue strength of steel increases from 440 MPa to 495 MPa after adding 0. 11% Nb. The main reason is that niobium alloying refined the grain size of steel, promoted the precipitation of irreversible hydrogen trap of NbC in steel, and increased the amount of prior austenite grain boundaries, the proportion of lowangle grain boundaries, the number of Σ3 grain boundaries, and the volume fraction of austenite in steel.