Stress-Corrosion Fracture of 12Kh18AG18Sh Steel in Chloride-Containing Media with Copper Cations

We studied the corrosion and corrosion-mechanical resistance of new austenitic high-nitrogen 12Kh18AG18Sh steel for the retaining rings of turbogenerators in aqueous solutions containing chlorides and copper (II) cations. A significant decrease in the corrosion resistance of this steel (P constitutes 0.52–14.50 mm/year) and in its resistance to corrosion cracking and corrosion-fatigue fracture in CuCl₂ solutions was established. We also calculated the coefficients of linear parts of the kinetic diagrams of fatigue fracture of the steel under study in air with a humidity of 40% and in 22% NaCl and CuCl₂ solutions.     

Corrosion of 12Kh18AG18Sh steel in contact with copper

The anodic dissolution rate of 12Kh18AG18Sh steel increases due to its contact with copper at temperatures of 65–100°C. The difference-effect coefficient is 0.375 at 75°C. A copper cathode is almost twice as efficient as a steel one, and an increase in its area results in a sharp increase in the corrosion current density of steel. We established experimentally that, in the temperature range 85–100°C, the formation of a galvanic element with copper leads to pitting corrosion of 12Kh18AG18Sh steel owing to polarization to a more positive potential than the pitting-formation one. But, at temperatures below 65°C, a protective effect caused by polarization to a more negative potential than the steady-state potential is observed. In this case, the current of anodic dissolution of copper grows insignificantly. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 35, No. 64, pp. 101–104, November–December, 1999.     

Pitting corrosion of 12Kh18AG18Sh steel in chloride solutions

We experimentally established that the corrosion rate of 12Kh18AG18Sh steel in a 22% NaCl solution in the temperature range 20–100°C does not exceed 0.22 g/(m²·h) (or 0.277 mm/year). The material undergoes self-passivation with the formation of a protective passive film of Fe₃O₄+(Fe, Cr)₂O₃+(Mn, Fe)₂O₃. Pitting resistance of steel decreases in solutions with a concentration of chloride ions of above 0.2 mole/liter and temperatures of at least 40°C. We studied selective dissolution of certain components of steel and found that manganese is most soluble. Ionization of chromium occurs more slowly than that of the iron matrix. As a result of selective dissolution of steel, the passive film is depleted of manganese and nitrogen. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 35, No. 3, pp. 81–85, May–June, 1999.     

稀土对1Cr18Ni9钢腐蚀性能及组织状态影响

利用化学法对1Cr18Ni9钢表面扩渗稀土,通过X－射线衍射分析了试样表面的组织状态。结果表明,1Cr18Ni9钢渗入稀土后,表面有CeFe7和LaO新相产生,并引起奥氏体含量降低,铁素体含量增加,改变了试样表面的微观结构。阳极极化曲线的测定结果表明,扩渗稀土后的1Cr18Ni9钢试样耐腐蚀性能超过了稳定化处理的1Cr18Ni9Ti钢水平。     

Electrochemical and Corrosion Properties of Hydrogenated 45 and 12KH18N10T Steels

We study the influence of the conditions of electrolytic hydrogenation of steels on their electrochemical and corrosion properties in a hydrogen galvanic couple (HGC) formed by the hydrogenated and nonhydrogenated metals depending on their structure and the pH value of the medium. On the basis of the polarization characteristics and corrosion mass losses of the hydrogenated 45 steel, we estimate the correlation between the parallel reactions of oxidation of hydrogen and iron in the HGC. Immediately after hydrogenation, the current of the HGC is limited by a flow of diffusion-mobile hydrogen desorbed from steel, and the fraction of the reaction of oxidation of iron constitutes about 20% of the total current. Under these conditions, the corrosion rate of the hydrogenated steel is 20–30 times higher than for the nonhydrogenated steel. In the course of time, both the total current and the current of oxidation of iron become weaker but the role of the latter increases. As compared with the HGC of pearlitic steel, the HGC of martensitic 45 steel absorbs smaller amounts of hydrogen and, therefore, is characterized by lower currents but longer periods of functioning. The decrease in the pH value of the medium decreases the electromotive force and the initial current of the HGC of 45 steel, which leads to the deterioration of the protective properties of surface oxide films. Hydrogen absorbed by 12Kh18N10T stainless steel intensifies its general corrosion in the HGC and makes it susceptible to pitting corrosion. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 4, pp. 66–76, July–August, 2005.     

Some Specific Features of Degradation of Superheater Tubes of the Boilers of Thermal Electric Power Plants Made of 12Kh18N12T Steel

We study the process of degradation and damage for superheater tubes of the pressure boilers of power plants made of austenitic chromium-nickel steel. The role of sensitization and partial sigmatization of austenitic steel in the embrittlement of the tubes is analyzed.__________Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 4, pp. 81–86, July–August, 2004.     

Influence of Chloride-Containing Media on the Pitting Resistance of AISI 321 Steel

Materials Science - We develop mathematical models used to describe the dependences of the critical pitting temperatures of AISI 321 steel in model circulating waters with pH 4–8 and a...     

Cr12钢冷冲模具加工过程中开裂原因分析

Cr12钢冷冲模具在电火花线切割过程中发生开裂,采用光学显微镜、扫描电镜、化学成分分析和硬度测试等方法,对模具开裂的原因进行了分析。结果表明：该Cr12模具开裂为脆性开裂,其主要原因是铬含量超标,同时锻造不充分,使得材料中的共晶碳化物多而粗大且呈严重网状聚集分布,成为应力集中源,在线切割加工过程中的加工应力和材料自身内应力的共同作用下萌生裂纹并扩展开裂。     

脱氧对碳钢耐点蚀性能的影响

选择四种不同脱氧程度的碳钢,在pH=10的3%(质量分数)NaCl溶液中进行极化试验,比较钢的点蚀诱发敏感性;在人造海水中进行模拟闭塞腐蚀电池试验和室内挂片试验,评价钢的点蚀扩展速度.结果表明:沸腾钢A,B钢中的主要夹杂物为橄榄状硫化物和土豆状氧化锰夹杂,镇静钢C,D钢的主要夹杂物为条片状硫化物夹杂和硅酸盐夹杂.在相同条件下,沸腾钢比镇静钢表现出更弱的点蚀诱发敏感性和更小的点蚀扩展速度.同是镇静钢,过低的磷含量可显著促进蚀孔的扩展.     

稀土对耐候钢耐蚀性能的影响研究

通过X射线衍射分析、电子探针和扫描电镜等手段对10PCuRE和10PCu耐候钢的表面锈层性能进行了研究,得到了10PCuRE钢致密锈层的种类、形成过程以及保护机理.通过对加稀土与未加稀土的耐候钢锈层的对比研究,可知稀土耐候钢的锈层分为两层,包括外锈层和均匀致密的内锈层,内锈层的组成相中超过80%为保护性的α-FeOOH.稀土促进了合金元素Cu在内锈层的富集,有利于保护性内锈层的生成,提高了钢基体的耐蚀性能.     

镍元素对新型压铸模具钢热稳定性的影响

对比研究了含镍1%(质量分数)和不含镍的新型压铸模具钢的热稳定性能及微观组织演变情况。两种材料采取相同的淬火工艺,再经多次回火达到相似的硬度,然后于600℃进行热稳定性实验,并采用SEM(扫描电子显微镜)和TEM(透射电子显微镜)对比分析了两种材料的淬火态及热稳过程中的微观组织的变化情况,探索了Ni元素的添加对材料热稳定性的影响。实验结果表明:Ni元素能够阻碍碳化物向基体中溶解,未溶的碳化物颗粒在晶界处能有效阻止原始奥氏体的长大,从而使材料允许的淬火加热温度提高。在相同的淬火条件下,Ni使得SDYZ1钢中的碳化物无法充分地固溶于基体,因而在回火过程中减弱了二次碳化物的析出强化效果,导致在热稳前期SDYZ1钢的硬度降低较快;Ni提高材料热稳定性能的优势可能需要在较高淬火温度下才能体现。     

Influence of Plasma Surface Layer on Wear Resistance of AISI4140 Steel

The results presented in this paper show that the composite plasma surface layers could improve the wear resistance of AISI 4140 steel for the case when high specific load appears at the contact zone. Composite surface layers consist of plasma nitrided and subsequent plasma deposited TiN or TiAIN. The significant differences in hardness and structures of outer hard layers, compared to the base material promote high drop of internal stress. Improvement of wear resistance for composite surface layers could be explained by decreasing stress gradient and better resistance to local plastic deformation at the wear zone compared to single hard surface layer.     

铜在碳钢中扩散及其对碳钢耐腐蚀性的影响

用水溶液电沉积法在碳钢表面电镀铜并进行高温扩散退火,用Den-Broeder法计算铜在碳钢中的扩散系数,研究了铜在碳钢中的扩散行为及其对碳钢耐腐蚀性的影响。结果表明,铜在碳钢中的扩散主要沿晶界进行,铜的扩散抑制了热处理过程中碳钢晶粒的长大。铜在碳钢中的扩散系数为1.11×10-16～3.03×10-11 cm2/s,扩散系数随着退火温度的提高而升高,随着铜浓度的提高而降低。铜在碳钢高温奥氏体区中扩散所需的激活能为126～167 kJ/mol,在高于低温铁素体+奥氏体混合区中激活能为90～108 kJ/mol。通过铜在碳钢中的扩散制备的Cu-Fe梯度材料,具有优良的耐腐蚀性。