Corrosion and tribocorrosion behaviors of AISI 316 stainless steel and Ti6Al4V alloys in artificial seawater

The corrosion and tribocorrosion behaviors of AISI 316 stainless steel and Ti6Al4V alloys sliding against Al2O3 in artificial seawater using a pin-on-disk test rig were investigated. And the synergistic effect between corrosion and wear was emphatically evaluated. The results show that the open circuit potentials of both alloys drop down to more negative value due to friction. The corrosion current densities obtained under tribocorrosion condition are much higher than those under corrosion-only condition. Friction obviously accelerates the corrosion of the alloys. The wear loss for both alloys is larger in seawater than that in pure water. Wear loss is obviously accelerated by corrosion. And AISI 316 stainless steel is less resistant to sliding damage than Ti6Al4V alloy. The synergistic effect between wear and corrosion is a significant factor for the materials loss in tribocorrosion. In this surface-on-surface contact geometry friction system, the material loss is large but the ratio of wear-accelerated-corrosion to the total wear loss is very low.

Investigation on Electron Beam Welded Copper to AISI 316 Stainless Steel Joints

Joints of copper and stainless steels are used in a er ospace applications. Production of these joints by fusion welding faces many dif ficulties. This may be due to the differences in their physical, metallurgical a nd mechanical properties. Electron Beam Welding (EBW) process has been found to be especially well suited in this area. Selection of the appropriate welding par ameters needs thorough investigations. These parameters include: preheat tempera ture (℃), welding current (I w), focusing current (I F), welding spee d (V), height between the gun and workpiece surface (H), scan width (S w) and shift distance (S). The present work aims firstly, setting the pr oper welding conditions to get sound joint between commercially pure copper (C10 200) and AISI 316 stainless steel plates 8 mm thickness. Secondly, investigate t he effect of Electron Beam (EB) shift, single-sided and double-sided welds on the mechanical, metallurgical and chemical properties of the weld bead. Due to t he high difference in thermal conductivity between copper and stainless steel, E lectron Beam (EB) was shifted towards copper with different values. These values were ranged from 0.3 to 0.9 mm in welding without preheating of copper plate an d from 0.1 to 0.4 mm with preheating. Number of joints were welded using variabl e EBW parameters in view to obtain the sound weld bead. These parameters are as follows: gradual reduction I w=51 to 49 mA, I F=845 mA, V=8 mm/sec , H=130 mm, S w=500 μm and S=0.4 mm. The investigation has shown t hat, the copper (C10200) plate must be preheated to get sound welded joint with AISI 316 stainless steel using the EBW process. The tensile fracture in all wel ded samples occurred in copper plate away from the weld bead. This reflects that the weld bead tensile strength is greater than the copper strength. The EB shif t has slight effect on hardness distribution through weld bead. The hardness val ue (H v) reduces in gradual manner from stainless steel hardness to copper one. The EB shift distance has no significant effect on the impact toughness.

渗碳对AISI 316不锈钢表面性能影响的研究

用低温渗碳技术对AISI 316不锈钢进行表面硬化处理,利用光学显微镜、显微硬度计、XRD以及电化学测试技术研究了渗碳对不锈钢表面显微组织和性能的影响。结果表明,通过渗碳处理可以在AISI 316不锈钢表面获得单相碳过饱和固溶体,不仅表面硬度得到显著提高,而且表面耐蚀性能也有所改善。

Sigma相对316不锈钢在熔融镁合金保护气中腐蚀行为的影响

选取了AISI316型奥氏体不锈钢在650-800℃范围内服役时间长达120 000h的管材,通过金相法和EDS分析证明了基材中含有Sigma相。主要研究了不锈钢中的Sigma析出相对AISI316型奥氏体不锈钢在熔融镁合金保护气(SF6)中腐蚀行为的影响。实验结果表明,含有Sig-ma相的316不锈钢实验到200h就发生了严重的晶间腐蚀。腐蚀产物中,首先形成Cr2O3然后连着CrxO3或CrxO4层,最表层是疏松的Fe3O4层与片状结构的Fe3O4和C混合层连接。

Microstructure evolution and mechanical properties of 316L austenitic stainless steel with aluminum addition by warm rolling

Microstructure evolution and mechanical properties of 316L austenitic stainless steel with aluminum addition by warm rolling at 550 ℃ were investigated. It is found that sample is composed of an ashen austenite matrix, a gray black ferrite phase and a small number of NiCx. The average grain sizes are 21.62, 19.66 and 19.49 μm for samples with the rolling deformation of 30%, 50% and 70%, respectively. The yield strength and tensile strength of samples with solid solution time of 30 min and deformation of 70% are higher. The fracture modes are similar and belong to toughness fracture. The fracture surfaces of the samples are composed of relatively large equal-axis ductile dimples （5-15 μm） and fine scattered ones around the dimples （〈 5 μm）. As the rolling deformation increases, the quantity of subgrain boundary increases and the 〈 101 〉 orientation is more prominent. {001 } 〈 110 〉 rotation-cube textures are present in ferrite phase of samples and weak Goss texture is formed in austenite pole images.

AISI316不锈钢腐蚀磨损交互作用的研究

采用电化学方法、微观形貌观察以及失重法分析研究了AISI316不锈钢和Al2O3陶瓷摩擦副在模拟海水中的腐蚀磨损行为，探讨了摩擦对不锈钢腐蚀行为的影响以及腐蚀磨损交互作用。结果表明，在本实验条件下摩擦作用显著增加了AISI316不锈钢的腐蚀倾向，其腐蚀率显著增加。纯磨损量占总腐蚀磨损量的76％～88％，材料的损失主要是由摩擦作用所引起，腐蚀磨损交互作用量占总腐蚀磨损量的12％-24％，腐蚀磨损交互作用是影响材料耐磨蚀性能的重要因素。

渗扩时间比对AISI 316不锈钢渗氮层组织与性能的影响

采用真空两段渗氮工艺,在不同的强渗、扩散时间下对AISI 316不锈钢进行渗氮处理,通过X射线衍射(XRD)、扫描电镜(SEM)、光学显微镜(OM)、显微硬度测试和摩擦磨损试验等分析了渗氮层的组织和性能。结果表明,经过12 h的真空渗氮后,AISI 316不锈钢表面形成了一层由γ′-Fe_(4)N、ε-Fe_(2-3)N和CrN等相组成的渗氮层,其表面硬度和耐磨性能相较于基体均有明显的提高。其中,渗扩时间比为1∶1(强渗6 h、扩散6 h)时的渗层厚度约为96μm,表面硬度约为1069 HV0.5,是基体表面硬度的4.5倍,在20 N载荷下的磨损量约为基体的1/3;渗扩时间比为1∶2(强渗4 h、扩散8 h)时的渗层厚度约为120μm,ε-Fe_(2-3)N相衍射峰增强,在20 N载荷下的磨损量约为基体的1/30。延长扩散时间能增加渗氮层厚度,改善表面形貌,进一步提高不锈钢的耐磨性。

氮等离子体浸没注入处理316不锈钢的抗点蚀性能研究

利用等离子体浸没技术进行低剂量注氮,对AISI 316不锈钢材料进行了表面改性研究.电化学测试实验显示N2+离子的注入能够显著改善316不锈钢的抗点蚀性能.基于X射线光电子能谱(XPS)、X射线衍射分析(XRD)、二次离子质谱(SIMS)等技术表征结果,系统分析了N2+离子注入导致了316不锈钢抗点蚀性能提高的可能原因.