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利用电化学工作站测试了经不同工艺热处理后X80钢在海水模拟液中的极化曲线,并采用慢应变拉伸试验(SSRT)对其在模拟海水环境中进行了应力腐蚀试验。用扫描电镜(SEM)观察试样的断口形貌,并结合腐蚀试验结果分析在模拟海水环境中X80钢的应力腐蚀开裂机理。极化曲线表明未经过热处理的X80钢耐蚀性最差,腐蚀电流密度最大,热处理有效改善了钢样在模拟海水中的耐蚀性能,在回火温度为650℃时,腐蚀电流密度最小;SSRT试验结果表明,热处理后试样的断裂强度和伸长率增加,说明应力腐蚀开裂敏感性降低,并且回火温度越高,应力腐蚀开裂敏感性越低;电镜扫描结果显示经热处理后的试样断口出现了韧性断裂特征,宏观断口出现颈缩,微观上也可以观察到韧窝。
The polarization curves of X80 steel in seawater simulated by different process heat treatments were tested by electrochemical workstation. The stress corrosion test was carried out in simulated seawater environment by slow strain test (SSRT). The fracture morphology of X80 steel was observed by scanning electron microscopy (SEM) and the stress corrosion cracking mechanism of X80 steel in simulated seawater environment was analyzed based on the corrosion test results. Polarization curve shows that the corrosion resistance of X80 steel without heat treatment is the worst, and the corrosion current density is the largest. Heat treatment can effectively improve the corrosion resistance of steel samples in simulated seawater. When the tempering temperature is 650 ℃, the corrosion current density is the least. The result of SSRT shows that the fracture strength and elongation increase after heat treatment, which indicates that the sensitivity of stress corrosion cracking decreases and the higher the tempering temperature is, the lower the susceptibility to stress corrosion cracking. The result of SEM shows that after heat treatment, The fracture appeared tough fracture characteristics, macroscopic fracture appear necking, microscopic can also be observed dimples.