水蒸汽含量对SA213T91钢650 ℃氧化行为的影响

研究了ASME213 T91钢(T91钢)650℃下在(Ar+H2O)气氛中不同含量的水蒸汽中的高温氧化行为.T91钢在5%、7%和10%Ar+H2O气氛中氧化10 h的氧化动力学曲线表明,在含5%H2O气氛中氧化时,动力学符合抛物线规律,在其余两种浓度下氧化遵从分阶段抛物线规律.随水蒸汽含量的增大,氧化速度明显增大.在T91钢表面形成了多层结构的氧化膜.氧化膜组成从外到内依次为Fe2O3,Fe3O4和(Fe,Cr)3O4.探讨了不同含量的水蒸汽对T91钢氧化行为的影响机理     

T92 钢在高温水蒸气中的氧化行为

目的研究T92钢在90%Ar+10%H2O(均为体积分数)气氛中750℃条件下的氧化行为。方法在管式炉中进行高温氧化实验,利用SEM/EDS和XRD分析氧化膜的形貌、结构和成分。结果 T92钢在高温水蒸气环境中,氧化初始阶段的氧化产物为Fe2O3和FeCr2O4。随后的氧化过程中,Fe快速向外扩散,氧化加速。最终的氧化膜呈双层结构,内层为Fe2O3和FeCr2O4,外层为Fe2O3,氧化层内存在孔洞,且有裂纹。结论 T92钢在氧化初期不生成保护性富Cr氧化膜,在高温水蒸气环境中的氧化严重。     

T91钢超音速电弧喷涂45CT涂层在90%Ar+10%H2O气氛中的循环氧化行为

采用超音速电弧喷涂方法在T91钢上制备了45CT涂层,研究了样品在800℃和850℃的90%Ar+10%H2O气氛中的循环氧化行为,利用XRD和SEM/EDS分析了涂层氧化前后的表面成分和结构。结果表明:氧化后表面的氧化物主要由Cr2O3,NiCr2O4及NiO组成,850℃氧化后的表面氧化物还含有Fe2O3;45CT涂层在800℃下表现出良好的抗氧化性能,而在850℃氧化时,涂层出现裂纹,Fe通过裂纹快速向外扩散,导致涂层在氧化过程中失效。     

锅炉管材在高温烟气及烟灰中的耐蚀性

采用高温模拟腐蚀试验、腐蚀形貌观察及腐蚀产物成分分析等方法考察了304不锈钢、T91不锈钢和TP347不锈钢在模拟燃准东煤工况下的腐蚀行为。结果表明:304不锈钢的耐蚀性与TP347不锈钢的接近,优于T91不锈钢的。304不锈钢表面含Cr氧化层的形成提高了试样耐高温腐蚀性能,而TP347不锈钢在SO2气氛下形成的低熔点共晶物Ni2S3会导致反应物在腐蚀层中扩散,从而导致其腐蚀比304不锈钢的严重;T91不锈钢的Cr含量最低,所以耐蚀性最差。     

喷丸处理提高奥氏体耐热钢抗氧化性能的研究及应用

在650 ℃的水蒸气中对喷丸处理和未经喷丸处理的TP304H钢和Super304H钢的氧化行为进行了研究.使用GIXRD,SEM和EDX对氧化膜进行了分析.结果表明,喷丸使TP304H和Super304钢的抗氧化性能显著提高.TP304H钢经喷丸处理后提高抗氧化性能的效果优于Super304H钢.喷丸在奥氏体钢表面产生的超细晶粒和滑移带促进了Cr向表面扩散并形成富Cr的氧化物.喷丸诱发的马氏体对Cr的扩散及氧化行为也起着重要作用.对经内壁喷丸处理和未处理的TP304H钢制成的锅炉再热器管,在实际工况下服役7474 h后,经过内壁喷丸处理的TP304H钢管,内壁氧化膜的厚度只有未喷丸管子氧化膜厚度的约3％.实验室短期试验及实际应用均表明,传统钢材TP304H制成的锅炉管,内壁进行喷丸处理是提高抗水蒸气氧化性能的有效途径.     

T91钢在超临界水环境中的腐蚀性能

在超临界水(SCW)环境中对新型铁素体/马氏体钢T91进行了不同时间的高压釜浸泡试验,采用SEM、EDS和XRD等方法对试样表面的腐蚀氧化膜进行了分析。结果表明:T91钢在超临界水环境中的氧化符合固态生长机制,材料表面生成了保护性氧化膜;外层氧化膜的主要成分是Fe_3O_4,有大量孔洞和裂纹缺陷;内层氧化膜的主要成分为Fe_3O_4和FeCr_2O_4,结构致密,随浸泡时间的延长氧化膜分层逐渐清晰;内层氧化膜中FeCr_2O_4含量逐渐增加,Fe(Fe,Cr)_2O_4的尖晶石结构具有保护性,使T91钢在SCW中的腐蚀速率降低。     

PCrNi3MoVA钢表面溅射NiCrAlY涂层的高温氧化行为

用磁控溅射方法在PCrNi3 MoVA钢表面制备NiCrAlY涂层,涂层在空气中850 ℃恒温氧化100 h,借助XRD、SEM和EDAX对涂层表面氧化膜进行分析,检测其恒温抗氧化能力.结果表明,涂层大大提高了基体的抗氧化性,涂层表面主要生成了与基体粘附性好的Al2O3氧化膜,在柱状晶间隙较大处生成了NiCr2O4氧化膜与Fe2O3氧化膜;同时涂层的Ni元素与基体的Fe元素发生了明显的互扩散,而Cr元素在界面富集,Al元素主要集中在表面和界面,与氧发生反应生成Al2O3.     

内壁喷丸处理对TP304H耐热钢锅炉管抗水蒸汽氧化性能的影响

将经表面喷丸处理和未处理的TP304H钢管安装于锅炉再热器的高温段运行7474h后,对内壁氧化膜进行形貌观察、能谱分析和X射线衍射分析。结果表明,喷丸处理可大幅度提高TP304H钢的抗水蒸汽氧化性能,氧化膜的生长速率显著降低且氧化膜的粘附性提高。显微分析表明,氧化膜由双层结构转变为单一高Cr氧化膜层,外层Fe的氧化层消失。分析认为喷丸在管子内壁产生的剧烈形变引起晶粒细化和马氏体相变,在高温下促进了Cr向表面扩散及生成富Cr的氧化层。     

T91钢高温高压水蒸汽氧化膜微观组织结构研究

利用扫描电镜和能谱仪对高温高压水蒸汽条件下的T91钢氧化层形貌和氧化膜成分进行观察和分析.结果表明:氧化层的外层主要是粗柱状晶组织,其根部为细等轴晶组织;内层是单相无晶界结构.在表面生成CrFe2O6氧化物的单相无晶界非晶体簿膜,它是在Cr、Fe与O的供应相对较充足的环境中,由直径约0.1～0.2 μm的纳米级CrFe2O6氧化物小粒子堆积而成;继续氧化时,在非晶体层表面生长出CrFe2O4氧化物晶体层,在该晶体层生长的初期,(Fe、Cr):O比与非晶体层一致,但Cr逐渐减少而Fe渐多,并且Fe、Cr离子在CrFe2O4氧化物晶体中严重缺位约37%.     

Al对高温合金高温抗氧化性能的影响

通过加入Al改善高温合金氧化膜的稳定性,并辅以微量强化元素Nb与合理的热处理工艺来提高高温合金抗氧化性。在真空感应熔炼炉中熔炼合金,利用扫描电镜、X射线衍射仪研究了Al元素对高温抗氧化性能的影响。结果表明:Al的加入提高了钢的抗氧化性,但含5%Al试样的氧化膜表面出现大量裂纹;合金氧化膜主要是由Cr2O3和具有尖晶石结构的FeCr2O4、Fe3O4以及少量Al3Fe5O12组成。     

纳米 Y2 O3 预处理对 T91 钢抗高温水蒸汽氧化的影响

目的研究纳米Y_2O_3预处理对T91钢抗水蒸汽氧化性能的影响,分析稀土元素作用的机理及长期氧化后的失效机制。方法采用将Y_2O_3、铝粉、粘结剂制备成料浆涂覆于T91钢表面,并在720℃水蒸汽中预处理48 h。预处理样品和空白样品同时置于在700℃高温水蒸汽中氧化,获取循环氧化动力学曲线并进行对比,检验预处理对提高材料抗高温水蒸汽腐蚀的效果。对氧化的样品采用XRD、SEM/EDS对氧化物结构、形貌、成分进行分析。结果预处理后在样品表面形成了含Y_2O_3的富铬氧化物薄膜。在高温水蒸汽环境的氧化过程中,试样处理600 h时,质量增加轻微,仅为0.152 g/cm2。但在600 h后质量增加明显,预处理膜层逐渐退化,表面出现Fe_2O_3突出物。空白样在腐蚀初期即明显增加,氧化70h后,质量增加达12.17 mg/cm2,氧化过程中可见氧化产物的剥落,氧化膜附着力差。结论纳米Y_2O_3预处理可提高T91钢抗水蒸汽氧化性能,但随着氧化时间延长,富铬氧化膜将逐渐退化。     

Effect of Shot Peening on the Oxidation Resistance of TP304H and HR3C Steels in Water Vapor

Oxidation behaviors of TP304H and HR3C steels with and without shot peening were investigated at 650?°C in water vapor. The oxide scales were studied with XRD, SEM and EDX. The results showed that the oxidation resistance of the steels was effectively improved by shot peening, especially for TP304H. The oxidation resistance of shot peened TP304H was even better than shot peened HR3C. The shot peening process produced an ultra-fine surface microstructure and plenty of slip bands which resulted in an enhanced Cr diffusivity to form Cr-rich oxides. The shot-peening process also induced martensite at the surface, which enhanced Cr diffusion and significantly affected the oxidation behavior of the TP304H steel.     

Effect of Shot Blasting on Oxidation Behavior of TP304H Steel at 610℃ -770℃ in Water Vapor

Shot blasting on a tube steel of TP304H can greatly improve the oxidation resistance at 650℃-770℃ in water vapor, by the presence of an appropriate blasting intensity. SEM and EPMA analysis indicated that the structure of the oxide scale turned from multi-layer to monolayer after blasting and Cr2O3 in predominant. The untreated sample characterized in multi-layer oxide was composed of Fe in the outer layer and Fe and Cr underneath. For blasted one, the increase of diffusion rate of Cr and the decrease of effective diffusion energy of scale led to a uniform Cr-rich oxide layer, which was dense and protective and the oxidation resistance was increased.     

P91和Super304H钢表面涂覆NaCl在高温水蒸汽中的腐蚀行为

在海洋性大气中,沉积在金属构件表面的NaCl在高温环境中可能导致金属加速腐蚀。在600 °C NaCl和水蒸汽环境中,研究了P91钢和Super304H钢的腐蚀行为。采用XRD,SEM/EDS对腐蚀产物膜相组成和形貌进行了分析。结果表明,P91钢和Super304H钢均表现为失重,受到严重腐蚀。样品表面的腐蚀产物层中有大量裂纹和孔洞,导致腐蚀产物大量剥落。P91钢表面腐蚀产物主要由Fe₂O₃组成。Super304H钢由 (Fe,Cr,Ni)₃O₄和NiO组成。由于Cr₂O₃膜在NaCl和高温水蒸汽中受到严重破坏,两种合金均遭到严重腐蚀,含Cr量较高的Super304H钢比P91钢腐蚀更严重,且有明显的晶间腐蚀发生。     

316NG不锈钢在高纯水环境中的腐蚀行为

通过腐蚀失重试验,获得了316NG不锈钢在高纯水环境中的腐蚀失重曲线及均匀腐蚀速率;采用XPS、XRD、SEM等手段对腐蚀产物的组成元素、物相、形貌进行了分析。结果表明:316NG不锈钢在高纯水环境中的平均腐蚀速率为0.05mm/a,远小于304NG不锈钢和321不锈钢的;腐蚀产物膜主要以耐蚀性强的磁铁矿Fe_3O_4、尖晶石类氧化物FeCr_2O_4和NiFe_2O_4、镍和铬氧化物及氢氧化物等形式存在,且(铬+镍)与铁的原子比高于基体的,说明316NG不锈钢具有良好的耐腐蚀性能。     

High-Temperature Oxidation Behavior of SIMP Steel at 800 °C

In this work, the high-temperature oxidation behavior of SIMP and commercial T91 steels was investigated in air at 800 °C for up to 1008 h. The oxides formed on the two steels were characterized and analyzed by XRD, SEM and EPMA. The results showed that the weight gain and oxide thickness of SIMP steel were rather smaller than those of T91 steel, that flake-like Cr₂O₃ with Mn_1.5Cr_1.5O₄ spinel particles formed on SIMP steel, while double-layer structure consisting of an outer hematite Fe₂O₃ layer and an inner Fe–Cr spinel layer formed on T91 steel, and that the location of the oxide layer spallation was at the inner Fe–Cr spinel after 1008 h, which led the ratio between the outer layer and the inner layer to decrease. The reason that SIMP steel exhibited better high-temperature oxidation resistance than that of T91 steel was analyzed due to the higher Cr and Si contents that could form compact and continuous oxide layer on the steel.     

304L不锈钢在高温高压水蒸气中的应力腐蚀开裂行为

目的 研究304L不锈钢在高温高压水蒸气中的应力腐蚀开裂行为及机理。方法 采用慢应变速率试验分别研究了304L不锈钢在常温常压水、高温高压水、高温高压水蒸气环境中的应力腐蚀开裂行为。利用SEM、三维立体显微镜和XPS,分析试样氧化后断口区域的形貌及元素分布。结果 304L不锈钢在常温常压水中的抗拉强度为730 MPa,拉伸率为94.32%。在高温高压水、高温高压水蒸气环境中的抗拉强度分别为382、379 MPa,拉伸率分别为44.98%、47.38%。304L不锈钢在三种试验环境中慢拉伸后的断口表面布满大量韧窝,断口全貌呈韧性断裂特征,高温高压水、高温高压水蒸气中试样的抗拉强度较常温常压水中明显下降。304L不锈钢在高温高压水环境和水蒸气环境中得到的XPS谱图中各结合能峰位置几乎相同,峰的相对强度因载荷的不同而发生变化。施加载荷后,在高温高压水环境中304L不锈钢表面氧化物中的Cr含量增加,而在高温高压水蒸气环境中的Cr含量略有下降。结论304L不锈钢在高温高压水和高温高压水蒸气环境中具有相似的最大抗拉强度和最大应变值。施加载荷将影响304L不锈钢氧化过程中金属元素扩散的速度,进而影响氧化产物的成分。     

Grain-Size Effects on the High-Temperature Oxidation of Modified 304 Austenitic Stainless Steel

The high-temperature oxidation behavior of modified 304 austenitic stainless steels in a water vapor atmosphere was investigated. Samples were prepared by various thermo mechanical treatments to result in different grain sizes in the range 8–30 μm. Similar Σ3 grain boundary fraction was achieved to eliminate any grain-boundary characteristics effect. Samples were oxidized in an air furnace at 700 °C with 20 % water vapor atmosphere. On the fine-grained sample, a uniform Cr₂O₃ layer was formed, which increased the overall oxidation resistance. Whereas on the coarse-grained sample, an additional Fe₂O₃ layer formed on the Cr-rich oxide layer, which resulted in a relatively high oxidation rate. In the fine-grained sample, grain boundaries act as rapid diffusion paths for Cr and provided enough Cr to form Cr₂O₃ oxide on the entire sample surface.     

Influence of water vapour on high temperature oxidation of steels used in petroleum refinery heaters

The oxidation behaviours of three different steels used in the construction of petroleum refinery heaters were investigated by thermogravimetric analysis (TGA) technique. C‐5, P‐11 and P‐22 steel samples were tested in two different environments: air and CO₂ + 2H₂O + 7.52N₂, a gas composition which simulates the combustion products of natural gas, at 450 and 500 °C. P‐22 steel had the best oxidation resistance at both temperatures in air. In CO₂ + 2H₂O + 7.52N₂ environment, the oxidations of all the steels were accelerated and C‐5 exhibited better oxidation resistance than P‐22 and P‐11. Analyses of oxidation products by optical microscopy, SEM‐EDX and XRD were carried out to correlate TGA results to oxide composition and morphology. The lower oxidation rate of P‐22 in air was explained with reference to the formation of a protective Cr‐containing oxide layer between the steel and the iron oxide scale. The higher oxidation rates of chromium containing steels in CO₂ + 2H₂O + 7.52N₂ environment were attributed to the depletion of protective Cr‐containing oxide scale, which was deduced from the lower Cr content of this layer than that formed in air oxidation, as a result of probably faster oxidation of Cr even inside the steel. Therefore, the oxidation mechanisms of Fe? Cr alloys with intermediate Cr contents at higher temperatures could also be valid for steels with low chromium contents such as P‐22 (2.25%) even at 450 and 500 °C.     

热带海洋大气环境下不锈钢的腐蚀寿命评估

目的 给出一种模拟万宁海洋大气环境的室内加速环境谱并对典型不锈钢材料进行寿命预测。方法 采用失重法对4种不锈钢的耐蚀性进行宏观分析。采用X射线光电子能谱分析仪（XPS）对4种不锈钢的腐蚀产物类型进行分析。采用扫描电子显微镜（SEM）对4种不锈钢的腐蚀产物进行微观分析。采用腐蚀电化学法对4种不锈钢进行宏观电化学分析。采用灰色关联度分析法研究室内加速环境谱与万宁海洋大气环境下户外暴露试验的相关性。结果 4种不锈钢的腐蚀失重速率都随着试验时间的增加而降低,其中430不锈钢腐蚀速率的减小程度最明显。4种不锈钢均在室内加速腐蚀试验中表现出较好的耐蚀性,耐蚀性由好到差依次为2205、316L、304、430不锈钢。XPS结果显示,304不锈钢与316L不锈钢的腐蚀产物主要为Fe₂O₃和Fe₃O₄;2205不锈钢的腐蚀产物主要包括Fe₂O₃以及Fe OOH或FeCr₂O₄;430不锈钢的腐蚀产物属于典型不锈钢的腐蚀产物,主要由...