Cr32Ni7Mo3N特级双相不锈钢的空蚀行为

Cavitation erosion behavior of Cr32Ni7Mo3N hyper duplex stainless steel

利用磁致伸缩空蚀试验机对Cr32Ni7Mo3N特级双相不锈钢在蒸馏水和人工海水中进行了空蚀实验,并采用扫描电镜跟踪观察了经不同时间段空蚀后试样的形貌.通过测量失重绘制了材料的累积失重量和失重率曲线.经电化学工作站测量了材料在静态与空蚀条件下的极化曲线和腐蚀电位变化.对比分析了Cr32Ni7Mo3N与SAF2205双相不锈钢在人工海水的抗空蚀能力.结果表明:Cr32Ni7Mo3N特级双相不锈钢空蚀破坏首先在铁素体薄弱区以及铁素体和奥氏体相界发生,并向铁素体内扩展,铁素体发生解离断裂脱落;奥氏体随着空蚀的进行,滑移线增多,显微硬度值增加,且人工海水中奥氏体显微硬度值比在蒸馏水中的高;铁素体大面积破坏后,奥氏体才失稳产生延性断裂脱落,奥氏体的存在延缓了破坏在整个材料表面上的扩展.空蚀与腐蚀交互影响导致材料在人工海水中加速破坏.Cr32Ni7Mo3N特级双相不锈钢在人工海水中的抗空蚀能力优于SAF2205双相不锈钢.

The cavitation erosion behavior of Cr32Ni7Mo3 N hyper duplex stainless steel in both distilled water and artificial seawater was investigated by a magnetostrictive-induced cavitation facility. The micrographs of damaged surfaces after cavitation for different intervals of time were observed by scanning electron microscopy（ SEM）. The cumulative mass loss curves and cumulative mass loss rate curves of specimens were drawn by measuring the weight loss. The polarization curves and free-corrosion potentials of specimens were measured by electrochemical workstation in the static state and in the cavitation erosion condition. A comparison of cavitation erosion resistance was performed between the material and SAF2205 steel in artificial seawater. The results show that cavitation damage firstly occurs in the ferrite weak areas and ferrite-austenite phase boundaries,then gradually expands to the ferrite phase,and the ferrite phase dissociates off at last. Its failure mode is cleavage brittle fracture. As the cavitation erosion time prolongs,the austenite phase microhardness value increases because of slip lines generating more. During the entire cavitation,the microhardness value of the austenite phase in artificial seawater is higher than that in distilled water. When the ferrite phase is largely destroyed,austenite phase damage begins to happen and drop off. Its failure mode is ductile failure. So the existence of austenite delays fracture expanding to the entire material surface. In artificial seawater,the interaction of both cavitation erosion and corrosion leads to material failure acceleration,and the cavitation erosion resistance of Cr32Ni7Mo3 N steel is better than that of SAF2205 steel.