镧和铈对Cr13型不锈钢耐腐蚀性能的影响

采用电化学交流阻抗谱法(EIS)和扫描电镜(SEM)等方法研究了含镧铈混合稀土对Cr13型马氏体不锈钢在3.5%Na Cl溶液中耐腐蚀性的影响。分析了交流阻抗等效电路图中电化学参数随稀土含量变化的演变规律。结果表明,相比未加稀土的钢,稀土含量为0.034%的钢在溶液中生成的锈层薄、致密且更具保护性;镧铈混合稀土提高了Cr13型不锈钢的耐腐蚀能力。     

固溶处理对双相不锈钢耐腐蚀性能的影响

研究了固溶处理对双相不锈钢组织和耐腐蚀性能的影响。结果表明,经固溶处理后,双相不锈钢钢组织主要为黑色铁素体和板条状、岛状的奥氏体。随着固溶时间(固溶温度1120℃)的延长,双相不锈钢中铁素体含量增加,奥氏体含量减少。随固溶温度(保温4 h)的增加,双相钢点蚀速率先减小后增大,耐应力腐蚀性能由好变差。随固溶时间(固溶温度1120℃)的延长,双相钢点蚀速率先增大后减小,在4 h时达到最小值0.05 g/(m~2·h);耐应力腐蚀性能增加,在4 h时最佳,腐蚀断裂时间为39 h。     

双相不锈钢焊接接头的耐腐蚀性能

根据母材临界点蚀温度(CPT)的试验结果,利用小试样的腐蚀实验方法研究了奥氏体-铁素体双相不锈钢焊接接头的耐点蚀性能.结果表明,手工电弧焊工艺过程对双相不锈钢材料的耐点蚀性能具有显著的影响,点蚀优先发生在焊缝金属或焊接热影响区中.双相不锈钢材料的耐点蚀性能与材料本身奥氏体和铁素体相比例有关.腐蚀试样的表面状态(粗糙程度)对母材金属的耐点蚀性能有明显的影响.表面越粗糙,耐点蚀性能越差,临界点蚀温度越低.     

稀土Ce对316L不锈钢耐腐蚀性能的影响

采用失重分析,扫描电镜(SEM),能谱分析(EDS),电化学阻抗谱(EIS)和动电位极化实验(DP)等方法研究稀土元素Ce对316L不锈钢在3.5%(质量分数) NaCl腐蚀环境中耐腐蚀性能的影响。结果表明,添加适量的稀土元素Ce可有效减小316L不锈钢在3.5%NaCl溶液中的重量损失,降低其腐蚀速率,减小腐蚀表面点蚀坑的尺寸与数量,提高316L不锈钢在3.5%NaCl溶液中的腐蚀电位,降低其腐蚀电流密度,增大容抗弧半径,提高耐蚀性能。因此,本文确定提高316L不锈钢在3.5%NaCl溶液中耐腐蚀性能的最佳稀土元素Ce含量为0.015%(质量分数),并进一步揭示了Ce改善316L不锈钢耐腐蚀性能的主要原因:Ce可有效降低有害元素S在晶界处偏聚,净化晶界;改善夹杂物的形貌,减小夹杂物的尺寸。     

不同焊接工艺对双相不锈钢力学性能及耐腐蚀性能的影响

采用三种不同的焊接工艺对双相不锈钢S31803进行焊接试验,通过对接头微观组织、力学性能、氧含量及耐腐蚀性能的观察与测试,确定最佳焊接工艺参数,并分析了焊接工艺方法对焊接接头组织、力学性能和耐腐蚀性能的影响。结果表明：与GTAW,SMAW相比,GTAW+SAW焊接工艺获得的接头的冲击吸收能量和耐腐蚀性能均可以满足双相不锈钢的制造标准要求,可以在压力容器制造中广泛使用。     

铈对S32750超级双相不锈钢低温冲击性能的影响

通过夏比冲击和示波冲击方法分析了两种Ce含量S32750超级双相不锈钢在20~－100 ℃范围内的冲击吸收能量及能量构成差异,利用Aspex自动扫描电镜分析仪、SEM、EDS研究了Ce对钢中夹杂物的改性行为及冲击断裂行为的影响。结果表明:高Ce试验钢的抗低温冲击断裂性能明显优于低Ce试验钢,前者韧脆转变温度相较后者下降16 ℃;Ce的添加使得试验钢－80 ℃冲击吸收能量提高45 J,其主要源于裂纹扩展能W_p的提升(76%)。冲击断口形貌观察和夹杂物分析结果显示,低Ce试验钢在－80 ℃冲击断口表现为完全解理断裂;相较于低Ce试验钢,高Ce试验钢中Al₂O₃夹杂显著减少,多为改性后的铈铝氧复合夹杂;硬脆Al₂O₃夹杂数量的减少有效改善了钢的冲击性能。     

氮对2205双相不锈钢在NaCl溶液中耐腐蚀性能的影响

在实验室条件下,以氮代镍冶炼节约型双相不锈钢2205-N,并采用电化学阻抗技术和电化学极化曲线法研究了试验钢在3.5%Na Cl(质量分数)溶液中的腐蚀行为。试验结果表明:在N含量(质量分数) 0. 11%～0. 35%范围内,随着N含量的增大,试验钢奥氏体相逐渐增多且晶粒细化、容抗弧半径逐渐增大、极化电阻R_p逐渐增大、腐蚀电流I_(corr)逐渐减小,2205-N双相不锈钢的抗腐蚀性随着N含量的增大逐渐增强。试验证明,以氮代镍生产节约型双相不锈钢是行之有效的。     

稀土镧对FeCrAl不锈钢高温力学性能的影响

探究稀土镧对FeCrAl不锈钢高温力学性能的影响。采用gleeble3500热应力/应变模拟机对添加0.052%La元素和不添加La元素FeCrAl不锈钢进行高温力学性能测试,运用金相显微镜和扫描电镜对试样拉伸后断口组织和形貌进行观察分析。结果表明：添加稀土镧可以提高FeCrAl不锈钢高温抗拉强度,并且消除FeCrAl不锈钢高温第三脆性区。分析断口形貌发现,高塑性区温度下的试样断口有明显韧窝,韧窝附近有较大塑性变形,断裂方式主要为穿晶断裂;低塑性区温度下的试样断口出现解理断裂,韧窝较浅,断裂方式主要为沿晶断裂。     

固溶处理对汽车用双相不锈钢组织与耐腐蚀性能的影响

对铸态00Cr22Ni5Mo3N双相不锈钢进行不同温度的固溶处理,通过OM、SEM、XRD、化学浸泡试验和电化学试验等方法,研究了固溶处理对00Cr22Ni5Mo3N双相不锈钢组织结构和耐腐蚀性能的影响.研究表明:经1050～1250℃,保温30min固溶处理的00Cr22Ni5Mo3N钢组织为铁素体+奥氏体双相组织....     

时效制度对2205双相不锈钢耐蚀性能的影响

以2205双相不锈钢板为研究对象,研究了时效温度、时效保温时间和冷却速度对不锈钢板动电位极化曲线的影响,观察了固溶和不同时效热处理制度下试样的微观组织形貌,分析了影响双相不锈钢板耐腐蚀性能的主要因素。结果表明,950 ℃时效时具有最好的耐腐蚀性能,而在时效温度为850 ℃时耐腐蚀性能最差;当时效后冷却方式由空冷变成水冷后,不锈钢的耐均匀腐蚀性能和抗点蚀性能都得到了改善。     

Microstructure and pitting corrosion resistance of annealed duplex stainless steel

The transition from metastable to stable pitting was studied in 0.5 M NaCl water solution for two cast duplex stainless steels under different microstructural conditions achieved by annealing in the range from 900 °C to 1200 °C. The ensuing microstructural changes in heat treated steels were defined and correlated with established pitting potentials (E_p) and sites of corrosion damage initiation. The variations in E_p have been discussed in terms of secondary phases precipitation. The critical condition for pit stability was quantified and used to select an appropriate microstructural state, resulting in the higher potential at which stable pit growth is first observed.     

Effect of cutting parameters on pitting corrosion resistance of S32760 duplex stainless steel

To improve the performance in service of S32760 duplex stainless steel (DSS) in the marine environment, the influence of cutting parameters of S32760 DSS on the pitting corrosion resistance of the workpiece is studied. Cutting experiments are performed on S32760 DSS by varying the cutting parameters to investigate their effects on the surface morphology. The electrochemical experiments are conducted on the workpiece immersed in the 3.5 wt% sodium chloride solution to investigate how the cutting parameters affect the pitting corrosion resistance of S32760 DSS. The results indicate that the pitting corrosion resistance is influenced by the cutting speed and feed rate, which in turn affects the surface roughness. The cutting depth does not have a significant impact on the surface roughness but significantly affects the pitting resistance. The recommended cutting parameters are as follows: feed rate of 0.1 mm/r, cutting speed of 130 m/min, and cutting depth of 0.4 mm.     

焊接方法对双相不锈钢焊接接头耐蚀性的影响

采用气体保护钨极氩弧焊（GTAW）、焊条电弧焊（SMAW）和埋弧焊（SAW）对2205双相不锈钢进行焊接,采用光学显微镜对接头组织进行观察,采用数点法计算铁素体相的含量,测定接头的耐点蚀和耐CO2应力腐蚀性能,研究焊接方法对接头耐蚀性的影响。结果表明,焊接方法影响焊缝组织形态及铁素体含量。GTAW焊缝由不规则的条状组织和两相交织分布的块状组织组成,而SMAW和SAW焊缝为方位不一的条状组织和少量的块状组织。GTAW和SMAW焊缝的铁素体含量为35％～55％,而SAW的不足20％。接头的耐蚀性与铁素体相比例密切相关,GTAW、SMAW和SAW的耐蚀性依次降低。从铁素体相比例和耐蚀性角度考虑,GTAW和SMAW能够获得满意的焊接接头。     

Co对CrNiMo双相不锈钢组织及耐蚀性能的影响

采用TIG粉末堆焊的方式,在304奥氏体不锈钢基板上制备Co含量分别为0％、1％、2％和3％的CrNiMo双相不锈钢堆焊层.经1100?℃固溶处理后,通过金相组织观察、显微硬度测试、动电位极化曲线和交流阻抗谱(EIS)测试研究了Co对CrNiMo双相不锈钢的显微组织、硬度及耐蚀性能的影响.结果表明:随Co含量的增加,C...     

固溶温度对2507双相不锈钢组织与耐蚀性能的影响

通过定量金相法、电化学试验和慢应变速率拉伸试验研究了固溶温度对2507双相不锈钢组织和耐腐蚀性能的影响,通过超景深观察了拉伸断口裂纹在2507双相不锈钢两相组织中的分布。结果表明,随着固溶温度的升高,2507双相不锈钢中铁素体相含量升高奥氏体相含量降低,1050℃时两相分布比较均匀相比例接近1∶1,有较好的抗点蚀和应力腐蚀性能;1000℃时有少量σ相在铁素体与奥氏体相界析出;此外2507双相不锈钢拉伸断口裂纹优先在铁素体中产生和传播,并终止于奥氏体。     

固溶温度对2507双相不锈钢力学性能及耐蚀性的影响

利用光学显微镜、扫描电镜、XRD、拉伸试验机和电化学综合测试仪等研究了不同固溶温度对2507超级双相不锈钢组织、力学性能和耐蚀性的影响。采用Thermo-Calc热力学软件计算了2507双相不锈钢的热力学平衡相图,并与测试结果进行了对比。研究结果表明,经1050 ℃及以上温度固溶后,σ相溶解;随着固溶温度的升高,铁素体相含量增加,奥氏体相含量降低,α/γ相体积分数比增加;1050~1100 ℃固溶30 min并水冷时,双相不锈钢具有较好的综合力学性能,屈服强度、抗拉强度和伸长率分别大于600 MPa、840 MPa和35%。1050 ℃固溶30 min时,双相钢可获得较好的耐蚀性能。     

时效温度对含Cu抗菌双相不锈钢力学及耐蚀性能的影响

通过SEM、EDS以及拉伸试验与电化学测试等手段,研究了时效温度对含铜抗菌双相不锈钢力学及耐蚀性能的影响。结果表明,时效处理析出的富Cu相有提高抗拉强度的作用;在540~580 ℃范围内,随着时效温度升高,富铜相粗化,材料抗拉强度及塑性下降,断口由韧性断裂逐渐向解理断裂转变;在30%醋酸溶液中,富铜相体积分数越大,试样耐蚀能力越强。     

Effect of nitrogen on corrosion of duplex stainless steel weld metal

Abstract

A type 329Jl duplex stainless steel was gas tungsten arc welded without filler material in an Ar–N₂ gas mixture atmosphere with the aim of changing only the nitrogen content in the weld metal. The effect of nitrogen on the microstructure and corrosion properties of the weld metal was examined. An increase in nitrogen partial pressure increased the nitrogen content of the weld metal and brought reductions in the ferrite content and the quantity of Cr₂N nitride precipitates. Three corrosion parameters, namely, critical pitting temperature (CPT), pitting potential, and corrosion rate, were measured for weld metals having different nitrogen contents. The CPT and pitting potential increased and corrosion rate decreased with increasing nitrogen content of the weld metal. The corrosion behaviour was explained in terms of changes in microstructure and pitting index depending on the nitrogen content of the weld metal.     

Effect of small additions of ruthenium on pitting corrosion resistance of LDX2101 duplex stainless steel

Four stainless steel alloys with ruthenium compositions of 0·16, 0·24, 0·32 and 0·64 wt-% were produced from pieces cut from commercial LDX2101 duplex stainless steel plate with the manufacturer’s composition of 0·03C–21·5Cr–1·5Ni–0·3Mo–5·0Mn plus pressed ruthenium powder with purity of 99·8%. After solution annealing the samples, the actual chemical composition was analysed using X-ray fluorescence analysis, and then, ASTM A923 (01·03) test method A – sodium hydroxide etch test for classification of etch structures of duplex stainless steel was used to analyse their microstructure. Corrosion potential and pitting potential of these samples were evaluated using a potentiodynamic polarisation technique, and the results were compared to corrosion and pitting potentials of the control alloy LDX2101. The tests for both produced and control alloys were performed in naturally aerated 3·56%NaCl aqueous solution at 25±2°C. The results indicated that small additions of ruthenium significantly improved the pitting potentials of the resulting alloys. The results also indicated that ruthenium additions have no detrimental effect to the microstructure of the resulting alloys. In addition, if such small additions of ruthenium will not improve the general corrosion of the resulting alloy, it will at least not have any detrimental effect on the resulting alloy. Ruthenium will also lower the current required to maintain the passive state of LDX2101 stainless steel. In addition to reduced current to maintain the passivity of LDX2101 stainless steel, ruthenium also increased the passive range of LDX2101 stainless steel.