Correlation Between Potentiodynamic Polarization Behaviors of Transient Liquid Phase Bonded 2205 Duplex Stainless Steel and the Bonding Constituents

In order to precisely evaluate the contribution of each bonding constituent to the pitting corrosion resistance of transient liquid phase (TLP) bonded 2205 duplex stainless steel (DSS), we have undertaken potentiodynamic polarization (PDP) and microstructural analytic measurements all across the TLP bonded area. The PDP results show that the pitting corrosion resistance of TLP bonded specimens is significantly affected by the presence of certain bonding constituents across the TLP bonded area. Electron microscopy analysis indicates that the formation of complex (Fe,Ni,Cr,Mo)₃P phosphide in the bonding zone (BZ) before the completion of isothermal solidification (IS) as well as the formation of P-rich sigma phase in the diffusion-affected zone (DAZ) following the completion of the IS provides the most preferential sites for the occurrence of pitting corrosion. The PDP results also confirm that the pitting potentials (E_pit) of the TLP bonded specimen before and after IS completion are, respectively, closer to the E_pit of the BZ and the E_pit of the DAZ rather than to those of other TLP BZs.

     

Microstructures,Mechanical and Chemical Properties of TLP-Bonded Joints in a Duplex Stainless Steel with Amorphous Ni-Based Insert Alloys

The changes in tensile strength and pitting corrosion resistance of transient liquid-phase (TLP)-bonded joints for a duplex stainless steel with MBF-80, MBF-30, and MBF-35 as functions of holding time and filler were interpreted with respect to the bond microstructure. Using MBF-80 after 300 seconds, the fracture strength of the joint reached the maximum value. The failure was dependent on the interplay between the reduction in residual liquid and the increase in interface precipitates. After 3600 seconds, the joint strength had the minimum value. At the same conditions, the tensile strength for MBF-80 was low compared with MBF-35 and MBF-30. In contrast with the tensile strength, the joint produced with MBF-80 for 3600 seconds exhibited the best corrosion resistance. Among the fillers used, the corrosion resistance of the joint using MBF-80 close to that of the substrate could be related intimately to the existence of Cr in this filler.     

What destroys the joint in rheumatoid arthritis?

The immunological disturbance in rheumatoid arthritis (RA) gives rise to a nonspecific inflammatory reaction mediated by cells and cytokines. This immunological nonbacterial synovitis, however, does not destroy the articular cartilage. The destruction of joint structures is the effect of tumor-like aggressive synoviogenic cell elements (TLP). These TLP formations are not observed in any other type of arthritis. TLP formations are strictly avascular and short-lived. After they have decayed, a collagenous pannus remains. Invasion and destruction of joint structures are brought about by several types of proteases, synthesized and secreted by highly active TLP cells. The TLP formations possess more than twice the affinity for adjacent bone than for the articular cartilage. In these formations, four oncogenes could be identified. In the course of RA disease, TLP formations can recur. Thus, the joint damage can summate with time. The oncological character of the aggressive process in RA demands new therapeutical considerations to protect RA patients from destruction of their joints.     

An Investigation on High-Temperature Oxidation and Hot Corrosion Resistance Behavior of Coated TLP (Transient Liquid Phase)-Bonded IN738-LC

Despite all achievements to improve nickel-based superalloy, these classes of alloys are still prone to degradation via high-temperature oxidation and hot corrosion. Repairing damaged parts could decrease the life cycle, cost of equipment, and a transient liquid phase (TLP) bonding is a favorable method that has successfully been used for this purpose. One way to increase the lifetime of the repaired parts and the main body is to utilize protective coating. In the current study, aluminized coating was applied on IN738-LC which was first bonded by TLP process. Coating performance on the joint centerline compared to the other parts of the sample was investigated using a scanning electron microscope (SEM and FESEM) and X-ray diffraction method (XRD). The oxidation test result showed that coating provided less protection on the joint centerline due to coating’s chemical composition difference in this area: particularly Fe and Cr. XRD results showed that at the initial time of oxidation, all (α, γ, δ and θ)-Al₂O₃ were formed and by prolonged exposure were transformed to α-Al₂O₃. The hot corrosion test also proved that the joint centerline and the diffusion-affected zone were less resistant to the corrosion attack of 3Na₂SO₄?+?NaCl salts and severity of damage in these zones were clearly distinguished from microscopic images.     

新型汽车排气系统用铁素体不锈钢的冷凝液腐蚀

为了开发既经济又具有良好耐冷凝液腐蚀性能的汽车排气系统用不锈钢,采用冷凝液腐蚀试验方法,对一系列的铁素体不锈钢进行了10周期的腐蚀评价研究。研究结果表明:Cr当量高于17%的铁素体不锈钢与Cr的质量分数为17%的铁素体不锈钢耐冷凝液腐蚀性能相当,且平均腐蚀失重量均小于6 g/m2,平均最大腐蚀深度均小于0.03 mm。在此试验结果的基础上,对新开发的439M型铁素体不锈钢和409L型铁素体不锈钢进一步开展5、10、20周期的冷凝液腐蚀试验,并使用极值分析方法对三种周期冷凝液腐蚀试验后样品的最大点蚀深度进行统计分析,研究结果表明,新开发的439M型铁素体不锈钢的预测寿命是409L的1.6倍。     

低合金结构钢腐蚀的影响因素及其耐蚀性判据

通过对不同厂家或产线生产的相近成分和显微组织的8种低合金工程结构钢样品进行中性盐雾加速腐蚀试验,结合成分测试、微观组织分析、腐蚀产物分析及数据统计与计算拟合等方法,提出了评价低合金结构钢耐蚀性的综合耐蚀指数及其包含钢材成分、夹杂物、组织及晶粒度等多因素的数学表达式。研究结果表明,低合金工程结构钢的耐蚀性除与传统的耐蚀指数I相关外,还受钢中夹杂物、显微组织、晶粒度等多种材料因素的耦合影响,其影响程度按从大到小排序依次为耐蚀合金元素所决定的耐蚀指数I、夹杂物总量、珠光体含量和晶粒度级别。综合耐蚀指数Y可作为比耐蚀指数I指数更有效的低合金钢耐蚀性判据,具有重要的工程应用价值。      

新型低铬镍高硅双相不锈钢的组织及其腐蚀行为研究

设计了新型低铬镍高硅双相不锈钢的组织及其化学成分，采用金相显微镜、Ｘ射线衍射、扫描电镜和多种腐蚀方法研究了本试验钢的组织及其腐蚀行为。试验结果表明这种钢在高温浓硫酸介质中具有良好的耐蚀性、抗晶间腐蚀、点蚀、电化学腐蚀性能以及高的塑韧性。     

新型镍铸铁的组织与性能的研究

设计了新型耐蚀镍铸铁的组织及其化学成分。试验结果表明，除了石墨和奥氏体基体外，还有合金渗碳体存在。该镍铸铁具有良好的耐蚀性能、较好的机械性能与满意的铸造性能。     

新型双相铸造不锈钢的组织及其磨蚀行为研究

研究了新型双相铸造不锈钢的化学成分、组织及其腐蚀与磨蚀行为。结果表明,该钢在含有固相颗粒的高温碱介质中具有良好的耐腐蚀与耐磨蚀性能。此外,还具有较好的力学性能和铸造性能,而且成本较低,具有广阔的工业应用前景     

新型汽车排气系统用铁素体不锈钢的冷凝液腐蚀研究

 铁素体不锈钢中Cr元素对其耐腐蚀性能起着非常重要的作用。本文采用实验室冷凝液腐蚀实验方法,对一系列汽车排气系统用铁素体不锈钢在实验室模拟冷凝液中的腐蚀性能进行了研究。所有钢种经过10周期的实验室冷凝液腐蚀实验后,研究结果表明：Cr当量高于17%的铁素体不锈钢与含17%Cr的铁素体不锈钢耐实验室冷凝液腐蚀性能相当,且平均腐蚀失重量均小于6g/m2,平均最大腐蚀深度均小于0.03mm。在此实验结果的基础上,对新开发的439M型铁素体不锈钢和409L型铁素体不锈钢进一步开展5周期、10周期、20周期的实验室冷凝液腐蚀实验,并使用极值分析方法对三种周期冷凝液腐蚀实验后样品的最大点蚀深度进行统计分析,研究结果表明,新开发的439M型铁素体不锈钢的预测寿命是409L的1.6倍。     

几种铜合金冷凝管新材料的研制

通过适当调整铜合金冷凝管的主要合金成分,或添加少量其它元素,以提高冷凝管的耐腐蚀性能,延长其使用寿命。结果表明,在铜锌合金中,加入少量的铝和镍,可较明显地提高原合金的综合耐腐蚀性能,能在沿海电站、或不良的淡水水质条件下使用。合金易于塑性加工成管材。     

表面高硬度和耐腐蚀性高强贝氏体钢制备新工艺

 铁路运输和工程机械等领域对贝氏体钢的耐磨性和耐腐蚀性具有较高的要求,而表面渗硼、渗铬处理是常见的提高表面硬度和耐腐蚀性的有效方法。在已有的研究工作中,获得贝氏体基体的等温淬火热处理和表面改性处理是分开进行的,工序复杂且生产成本增加。提出制备表面高硬度、高耐腐蚀性中碳高强度贝氏体钢的新工艺,将表面改性处理和贝氏体等温淬火工艺一体化,既可以简化制备工艺,又降低了生产成本、减少了环境污染。采用渗硼/铬-等温淬火一体化新工艺制备表面高硬度、高耐腐蚀性中碳高强贝氏体钢,通过组织观察、硬度测试和腐蚀试验等,对比分析了渗硼-等温淬火和渗铬-等温淬火一体化工艺对中碳高强贝氏体钢组织和性能的影响。结果表明,与仅经过等温淬火工艺处理相比,渗硼/铬-等温淬火一体化工艺处理后,贝氏体钢表面均形成了维氏硬度超过1 500HV的渗层(约为贝氏体基体硬度的3.3倍),且在0.5%NaCl溶液中的腐蚀性能明显提高。暴露在0.5%NaCl溶液中3 h后,渗硼层表现出更好的耐腐蚀性能。两种一体化工艺均可制备表面渗层、基体以贝氏体相为主的新型高强贝氏体钢,在相同处理时间下,与渗铬-等温淬火一体化工艺相比,渗硼-等温淬火一体化工艺处理的渗层生长速率快,且渗硼层与贝氏体钢基体的结合强度更高。     

大气腐蚀在低合金钢显微组织中的发生与发展

采用光学金相技术结合交流阻抗测量,分析了三种低合金钢在模拟的沿海大气环境中的初期腐蚀行为.实验发现,显微组织直接决定钢的初期腐蚀行为并间接影响长期腐蚀行为.在腐蚀初期,铁素体钢中的大角晶界易于被择优腐蚀,而贝氏体内的小角晶界的择优腐蚀趋势较弱,铁素体+珠光体钢的择优腐蚀集中于珠光体及其边界.铁素体裸钢有较强的耐腐蚀性,但其锈层电阻随腐蚀时间增加产生的增量较小;贝氏体与铁素体+珠光体裸钢的耐腐蚀性较差,但其锈层电阻随腐蚀时间增加产生的增量较大,长期腐蚀性能更优.这些结果表明,在适当合金化后,贝氏体作为新型低成本高强度耐候钢的基本组织极具应用潜力.     

Corrosion Behavior of Cr Micro-alloyed Corrosion-resistant Rebar in Neutral Cl——containing Environment

A new low-cost corrosion-resistant rebar(HRB400R)was designed and fabricated by Cr micro-alloying.The HRB400 Rrebar had uniform distribution of Cr element in ferrite grains.The corrosion behavior of the rebar in the neutral Cl~--containing environment was studied systematically,and the improved corrosion resistance of the HRB400 Rrebar was revealed.According to the corrosion-morphology observation and electrochemical monitoring during the constant immersion corrosion in the 3.5mass% NaCl solution,the HRB400 Rrebar presented alleviated corrosion damage,nobler Ecorr,lower Icorr,and larger Rtvalues,and these phenomena were more remarkable in the initial corrosion period.The elevated electrode potential of the rebar,caused by the solid-solution of Cr micro-alloying in the ferrite grains,was the key to the corrosion-resistance improvement.The HRB400 Rrebar also presented much lower mass-loss rate in the salt spray corrosion test.Besides the elevated corrosion resistance of the matrix,the doping and enrichment of Cr element in the rust layer was another factor for the higher corrosion resistance,which retarded the penetration of aggressive medium through the rust layer.     

新型船舶用铸造铝合金腐蚀性能研究

对比研究了新型铸造铝合金的耐蚀性，其耐海水和盐雾腐蚀性能优异，高于ZL101合金，与ZL305合金相当，应力腐蚀倾向小，优于LZ305合金，已用于船用耐蚀铸件。     

20Cr2Mo抽油杆用热轧圆钢的开发

20Cr2Mo是一种新型抽油杆钢。其主要特点是强度高及抗H2S腐蚀。根据用户的生产技术协议,进行了生产试验,解决了硬度高、钢材端部裂纹的技术难题。钢材的化学成分、力学性能、抗腐蚀性能满足用户要求。     

镀锌层表面新型环保钝化膜的耐腐蚀性能

 通过扫描电镜、辉光光谱、电化学测试、盐雾实验及湿热实验等手段探讨了用于钢板镀锌层表面A、B两种新型环保钝化膜的微观状态和耐腐蚀性能。结果表明：A型环保钝化膜的耐腐蚀性能明显优于传统铬酸盐钝化膜;B型环保钝化膜的耐腐蚀性能略低于传统铬酸盐钝化膜;并讨论了A型环保钝化膜耐腐蚀性能优异的原因。     

国内外高氮马氏体不锈轴承钢研究现状与发展

 高碳铬不锈钢是应用最为广泛的不锈轴承钢,其具有较高的硬度和一定的耐蚀性,然而较高的碳、铬质量分数导致粗大碳化物的出现,轴承钢的疲劳和耐蚀性能将受到损害。相比之下,钢中添加氮元素能够减少粗大共晶碳化物的数量,同时析出大量细小的氮化物及碳氮化物,氮代碳既强化基体又改善耐蚀性,从而获得高强度与良好耐蚀性。介绍了含氮轴承钢及含氮马氏体轴承钢的发展历程,分析了不锈轴承钢中氮元素对组织结构、力学性能和耐蚀性能的作用机理;介绍国内外含氮轴承钢的研究现状并指出了含氮轴承钢研究的不足,需要在氮溶解模型、氮对组织演变及耐蚀机制等方面进行基础理论研究,同时不断研发不同系列的含氮马氏体轴承钢。     

多元合金化双相铸造不锈钢Cr22Ni5Mo4Cu3.5的组织与性能

试验结果表明,所研制的Ｃｒ２２Ｎｉ５Ｍｏ４Ｃｕ３．５钢,经１０５０℃＊２ｈ水冷固溶处理后,具有良好的耐均匀腐蚀性能,较好的抗晶间腐蚀与抗点能力。此外,新型钢还具有良好的综合力学性能和工艺性能。