温压烧结316L不锈钢组织和耐3.5 wt. % NaCl腐蚀行为

Microstructure and anti-corrosion behaviors in 3.5 wt. % NaCl of warm compacted and sintered 316L

摘要:

采用温压成形和真空烧结制备316L奥氏体不锈钢，研究烧结温度对材料相组织和硬度、抗拉强度等力学性能的影响，结合腐蚀失重曲线、阳极极化曲线、Nyquist图、Mott-Schottky曲线分析研究温压烧结316L不锈钢在3.5 wt. % NaCl溶液中的浸泡腐蚀行为。利用扫描和激光共聚焦电子显微镜分析表征拉伸断口形貌及浸泡腐蚀形貌，X射线光电子能谱分析仪分析浸泡腐蚀600 h后的元素价态及钝化膜成分。结果表明:115 ℃温压成形、1290 ℃真空烧结的316L不锈钢密度达到最高（7.203 g/cm3），伸长率（65.46%）、抗拉强度(420.368 MPa)和硬度(63.1 HRB)最大；拉伸试样断口呈现明显的韧性断裂，韧窝深、数量多，韧性较好；亦在600 h浸泡腐蚀后，呈现最小的腐蚀电流密度(5.068×10-5 A?cm-2)和载流子密度(7.23×1019 cm-3)，最高的电荷转移电阻(8111 Ω?cm-2)和钝化膜电阻(14780 Ω?cm-2)，耐腐蚀性能最优。

Abstract:

316L austenitic stainless steel samples were prepared by warm compacting and vacuum sintering powder metallurgy method. Effects of sintering temperature on microstructure, phase and mechanical performances such as hardness and tensile strength was investigated. And corrosion weight loss curve, anodic polarization curve, Nyquist diagram and Mott-Schottky curve were studied to investigate the immersion corrosion behaviors of the sintered 316L austenitic stainless steel in 3.5 wt. % NaCl solution. Tensile fracture，immersion corrosion morphology and passivation film composition and elemental valence was analyzed by SEM (Quanta 450 FEG), laser scanning confocal microscopy (LSM 800) and XPS (AXIS Supra) respectively. Results shown that the highest sintering density (7.203 g?cm-3),elongation(65.46%), mechanical tensile strength (420.368 MPa) and hardness (63.1 HRB) are achieved after the samples were warm compacting at 115 ℃ and vacuum sintering at 1290 ℃, and presented high toughness with the tensile fracture morphologies of ductile rupture, deep and numerous dimples. In addition, the lowest corrosion current density (5.07×10-5 A?cm-2), the carrier density (7.23×1019 cm-3), the highest charge transfer resistance (8111 Ω?cm-2) and passivation film resistance (14780 Ω?cm-2) among the sintered samples after 600 h immersion in 3.5 wt. % NaCl exhibited very good corrosion resistance.