Interkristalline Korrosion von Auftragschweißungen einer FeCrNiSiMn-Legierung EB9/300rc

Intercrystalline corrosion of weld claddings of FeCrNiSiMn alloy type EB9/300rc The corrosion resistance against intercrystalline corrosion (IK) of weld claddings from the electrode EB9/300rc (alloy type FeCr18Ni8Si4Mn with ca. 18% δ-ferrite) has been investigated using electrochemical potentiodynamic reactivation (EPR) technique, the Straußtest, metallographic and microstructure analytical methods (REM, ESMA). In spite of the brittleness of the claddings investigated, the Straußtest failed in assessing sensitization of the (unbent) specimen. In the EPR double loop test in 0,5 M H₂SO₄ + 0,01 M KSCN at 30°C with a scan rate of 5 mV/s the extend of sensitization is indicated by the ratio of reactivation to passivation charge. Additional assessment of the microstructure of heat treated specimen enabled us to set up a grain disintegration diagram. Sensitization has been caused by precipitation of Cr-rich carbides and s?-phase at the grain boundaries and by decomposition of δ-ferrite followed by selective dissolution (?Ferritpfad”? corrosion). In the as welded state the claddings are not susceptible to IK.     

Nachweis der IK-Beständigkeit von verschleißfesten Auftragschweißungen mit dem EPR-Verfahren und mit Salpetersäure-Flußsäurelösung

Investigation of the resistance against IGA of wearfacing weld claddings by using the EPR test and nitric-hydrofluoric acid solution The corrosion resistance against intergranular attack (IGA) of weld claddings from the electrode Tube S 17 8 Si (alloy type FeCrl8Ni8Si4Mn with ≤ 18% δ-ferrite) has been investigated using electrochemical potentiodynamic reactivation (EPR) technique, the nitric-hydrofluoric acid (SF) test according to ASTM A 262 practice D, metallographic and microstructure analytical methods (SEM, EDX). Samples produced by different welding techniques (shielded arc and open arc) and partly additional thermal treated have been investigated. In standardized SF-solution and in 2 M HNO₃ + 0.05 to 0.5 M HF at 30°C there is no correspondence between corrosion rate and IGA-susceptibility, possibly caused by inhibitive action of Fe-III-ions. SF etchants evaluate Cr-depleted zones and decomposed δ-ferrite. In the optimized EPR double loop test in 0.5 M H₂SO₄ + 0.01 M KSCN at 30°C the extend of sensitization is indicated by the ratio of reactivation to passivation charge with additional assessment of the microstructure. It is shown that the EPR-test in the evaluated manner is able to find out IGA at claddings up to 30% δ-ferrite. In the as-welded state all claddings are resistant. Treatments at 400°C resp. 450°C were tolerated up to at least 1000 resp. 100 h. Sensitization may be caused by precipitation of Cr-rich carbides and by decomposition of δ-ferrite, for IGA the amount and distribution of ferrite plays a decisive role.     

Lochkorrosionsverhalten von Auftragschweißungen – Schweißlagen‐ und Oberflächeneffekte –

Pitting corrosion behaviour of built‐up welds – Effects of welding layers and tarnish – The pitting corrosion resistance of nickel based deposition welds on a superduplex steel made by active‐gas metal pulsed‐arc welding was studied. Therefore the determination of the CPT (Critical Pitting Temperature) should be carried out corresponding to ASTM G 48 C. However an unexpectedly low resistance of the built‐up welds also at multilayer order was noticed. After visual assessment of the examined specimens a significant effect of the surface condition was assumed. Because the CPT determination according to ASTM does not allow any statement about the corrosion process, this method was not suitable to characterize the corrosion system. For this reason a new method was applied to clarify the causes of the low corrosion resistance. This method determines the CPT with the help of the electrochemical current noise under the same conditions demanded in ASTM G 48 C. The temperature is increased continuously and the characteristic parameters of the system are recorded and evaluated objectively within short time. So it was possible to see the influence of the surface condition on the pitting corrosion behaviour of the examined specimens. The required parameters to the post‐processing of the deposition welds were determined. The comparison of the results show that the surface tarnish formed after the shielded arc welding process influences the pitting corrosion resistance negatively. After its elimination the CPT could be determined in dependence of the welding layers.     

Untersuchung der Korrosionsbeständigkeit von Auftragschweißungen der Hartlegierungsfülldrahtelektroden Stelly Fe12 und Stelloy 6

Investigation of the corrosion resistance of the hard-facing alloys stelloy Fe12 and stelloy 6 Cobalt hard-facing alloys are often used under complex conditions with combined wear and corrosion attack at higher temperatures. For using in equipments of atomic power plants cobalt free claddings are required to guarantee a low radioactivity level. Beside this there is an economic interest of the industry to use cobalt free welding filler metals. The problem consists in developing of cobalt free hard-facing alloys with the same wear and corrosion resistance as cobalt base alloys. The resistance of claddings of the electrode stelloy Fe12 with about 19% Cr and 10% Ni has been investigated in 0.5 M sulfuric acid at 66°C during a full immersion test in comparison with the cobalt base alloy stelloy 6. Both investigated materials have no satisfactory corrosion resistance. But according to the EPR-test they were resistant against intergranular attack (IK). The high matrix dissolution of grinded samples was disadvantageous to evaluate IK resistance by EPR-test.     

Korrosionsschutz durch Auftragschweißen mit der Titanlegierung Ti Code 12

Corrosion protection by weld surfacing with titanium alloy Ti Code 12

1 Vortrag, gehalten anläßlich der Achema-Tagung 1991, Frankfurt, 9.–15. 6. 1991

The chemical industry imposes very stringent demands on the corrosion resistance of the apparatus and machines employed. The use of the special metals, titanium and titanium alloys, as cladding materials for plant components exposed to severely corrosive environments is now standard practice in industry. Investigations with plasma hot wire weld surfacing have revealed the possibility of obtaining welded claddings by controlled heat transfer to the substrate and by shielding from the surrounding atmosphere. Because of the extremely high reactivity of titanium with noninert gases and metals, the investigations have been concentrated on minimizing reactions between gas and weld material and the associated formation of brittle reaction products during the weld surfacing process by optimizing the parameters and the application of supplementary inert gas shielding. In the course of these investigations, claddings have been produced by plasma hot wire weld surfacing on boiler plate, H II (material number 1.0425) with the use of the welding additive alloy, Ti code 12 (material number 3.7055). For suppressing or minimizing the formation of brittle reaction phases, an intermediate layer of nickel-based alloy was thereby applied by weld surfacing. This approach allows metallurgical bonding with titanium and provides high bond strength in the composite material. Subsequently, metallographic, microanalytical, and chemical corrosion analyses were performed for appraising the quality of the welded claddings.     

Korrosionsschutz durch Auftragschweißen mit den reaktiven Metallen Titan,Tantal und Zirkonium

Corrosion protection using surface-welded titanium, tantalum and zirconium claddings Very stringent demands are imposed on the corrosion resistance properties of components, apparatus, and plants of the chemical industry as well as in apparatus and machine construction. For technical and economic reasons, composite-layer materials which withstand the mechanical and corrosive conditions are employed. The special-purpose metals, titanium, tantalum, and zirconium exhibit high resistance to corrosion by many aggressive media, even at high pressure and temperature; these properties are not achieved by any of the conventional corrosion-resistant materials under the same conditions. The object of the research work was to develop a basis for producing claddings of titanium, tantalum, and zirconium by weld surfacing on a base metal of different composition with the application of the PHS method. Within the scope of the present project, single-layer claddings were applied by PHS weld surfacing with the use of titanium, tantalum, and zirconium of high purity as cladding materials on intermediate layers of nickel and copper, or alloys of these plasma hot wire weld surfacing, titanium, tantalum, zirconium, dilution, intermetallic phases, bonding, ductility elements. Boiler plate HI1 was employed as substrate for the three-layer composite materials. The titanium claddings thus applied have been thoroughly examined by metallographic techniques, layer analysis, and corrosion chemistry. The results indicate the possibility of producing corrosion-resistant claddings of titanium by the PHS method, provided that the welding process is shielded against contamination by atmospheric gases, and the formation of undesirable reaction products in the bonding zone between the base metal and filler material is minimized by means of an intermediate layer. The corrosion resistance of the surface-welded titanium claddings on an intermediate nickel layer coincides extensively with that of the reference material. On the basis of the corrosion analyses, the surface-welded titanium cladding on an intermediate copper layer is not resistant to corrosion. The results of weld surfacing with titanium have been applied to heterogeneous PHS weld surfacing with the special purpose metals tantalum and zirconium. In principle, metallographic examinations verify the possibility of producing a flawless bond between a cladding of zirconium and an intermediate nickel layer. In comparison with the filler material, Zr 702, however, the zirconium claddings applied by PHS weld surfacing exhibit a considerably greater hardness and low ductility. Because of the large difference between the melting points of tantalum and the substrate material, claddings of this kind cannot be reproducibly manufactured with sufficient quality by the PHS method, since the necessary parameters are at the extreme limit of the feasible range as far as the heat transfer is concerned.     

An ultra‐sulfur Hastelloy alloy C‐4

The effect of sulfur on solidification‐segregation and corrosion resistant properties of Hastelloy C‐4 corrosion‐resistant alloy was studied. It was found that strict controlling the content of sulfur can reduce the width and temperature interval of the solid‐liquid biphase region and the segregation degree of the alloy, resulting in a higher corrosion resistance. An improved low segregation Hastelloy C‐4 corrosion resistant alloy was developed.     

Electropolishing technique of Hastelloy C-276 alloy

Preparing a highly textured,flawless YBa_(2-)Cu_3O_7(YBCO)layer by ion-beam-as sis ted deposition(IBAD)requires a substrate with a smooth surface.In this paper,smooth tapes of Hastelloy C-276,a common template alloy,were prepared by electrochemical polishing,and the surface roughness the tapes was investigating by atomic force microscopy and scanning electron microscopy.By analyzing these results,it was discussed how the processing parameters affect the surface roughness,and it is found the following optimized processing parameters:current density of 0.104 A·cm~(-2),temperature of 50℃,plate spacing of 9 cm and time of 150 s.With these optimized parameters,the substrate roughness decreases to less than 5 nm,meeting the requirements of IBAD.     

Korrosionsverhalten von Plasma-Auftragschweißungen aus Titan-Legierungen

Corrosion behaviour of plasma-claddings from titanium alloys This paper is dealing with investigation results of plasma weld surfacing with the titanium alloys Ti grade 2 and 12 and the correlation between structure and corrosion properties of such claddings on interlayers of copper. First the developing of a process technique was important which allows an exact heat control during welding on copper and which ensures lowest dilution degrees between the materials. It was possible to produce two layered titanium claddings on a copper interlayer with a dilution percentage of smaller than 4% by using plasma-arc-powder surfacing with pulsed direct current. Optimized titanium claddings show structures without any defect and have a good adherence to the base material whereas high degrees of dilution effect the formation of intermetallic phases and inhomogeneities of the structure. The results of various corrosion examinations have shown that protective layers produced by plasma-arc-powder surfacing are comparable with rolled reference material.     

镍基耐蚀合金Hastelloy C-276锻造开裂原因分析

耐蚀合金Hastelloy C-276锻造过程中出现开裂,对其开裂原因进行了分析,并研究了均质化处理对其组织的影响以提高锻造成材率。结果表明,Hastelloy C-276合金铸态组织中存在大量μ析出相,是导致锻造开裂的主要原因。通过提高均质化加热温度和延长保温时间,可减轻枝晶偏析,经1170 ℃保温10 h空冷后,偏析几乎全部消失,锻造良好。     

晶界特征分布对哈氏合金力学性能的影响

采用扫描电镜、背散射电子衍射、透射电镜等手段对Hastelloy X(HX)合金的晶界特征分布、拉伸断口形貌及位错分布等进行研究。结果表明,HX合金室温拉伸断口由局部裂纹、微孔和大量的韧窝构成,微孔的形成与材料内部第二相颗粒分布有关。组织为晶内共格孪晶型的材料开裂是裂纹源扩展引起的,而组织为非共格孪晶型的样品是微孔聚集导致的开裂。分析表明,不同晶界特征分布的样品室温力学性能的差异,主要是晶粒尺寸和一次碳化物分布作用的结果。     

烟气脱硫装置用哈氏合金C-276的焊接

本文针对在烟气脱硫系统环境下使用的哈氏合金C-276的焊接特点,通过手工钨极氩弧焊、焊条电弧焊焊接工艺试验,表明所确定的焊接工艺参数合理、采取的工艺措施得当,避免了焊接缺陷的产生、获得了满意的焊接接头质量。     

Untersuchungen zur Qualitätssicherung beim Auftragschweißen von Korrosionsschutzschichten durch on-line Elementspektralanalyse

Investigations into quality assurance of plasma-welding corrosion-protective claddings using on-line element-spectrometry Cladding of high-grade corrosion resistent protective layers by means of plasma-welded claddings is applied with great success if the the geometry and size of the workpiece restricts the application of other coating-techniques. Especially if Ni-alloys which are sensitive to dilution are to be used the corrosion resistance is however reduced by changes of the chemical composition. By means of process optimization and a continuous control an evenly distributed and minimized dilution can be achieved. With a direct measuring of the element concentration in the weld pool of the plasma welding process it is attempted to improve process-control and quality assurance. The pursued aims in this respect are an increase of the performance of an on-line element spectral analysis of the plasma arc and their employment in the field of welding engineering. This contribution gives an overview of the conditions for an effective analysis method, requirements for the measuring set-up and the actual process as well as analytical approaches.     

Hastelloy C-276合金应力松弛试验及蠕变本构方程

对Hastelloy C-276合金分别在不同的温度(750、800、850和900℃)和相应的初始应力(250、250、250和200 MPa)条件下进行了多组应力松弛试验。利用试验测得的应力松弛曲线推导出应力松弛过程中蠕变应变速率与应力之间的关系,建立用于描述Hastelloy C-276合金应力松弛行为的蠕变本构方程,通过对蠕变应变速率—应力曲线进行拟合,得到各温度下蠕变本构方程中的材料常数。将蠕变本构方程带入有限元软件MSC.Marc对Hastelloy C-276合金的应力松弛过程进行模拟,模拟得到的应力松弛曲线与试验测得的应力松弛曲线符合得很好,验证蠕变本构方程的可靠性。     

42CrM0合金钢齿轮的焊接

1 问题的提出 作为公司主导产品的机械压力机,其传输动力的主要零件为全钢焊接齿轮.典型结构见图1.传统的压力机齿轮材质多为45钢,45钢齿轮经一定的热处理之后,性能基本能满足压力机的使用要求.但对于模数较小的压力机齿轮,或高速高负荷压力机,45钢齿轮在强度、耐磨、抗齿面点蚀、抗疲劳及使用寿命等综合性能方面,会显得不尽如人意.为适应国外先进的压力机已向合金钢齿轮发展的趋势,决定研制以42CrMo为代表的合金钢齿轮压力机.为此,首先需要解决42CrMo齿轮的焊接问题.42CrMo钢的化学成分和力学性能见表1.     

拉伸变形对Hastelloy C-276合金组织与力学性能的影响

采用金相(OM)、电子背散射衍射(EBSD)以及拉伸实验等技术手段研究了不同变形量条件下Hastelloy C-276合金薄板的组织演化特征和力学性能。结果表明:变形量小于14%时,位错优先在晶界附近塞积,并产生局部应变集中;变形量在14%~30%范围内,孪晶界附近及晶粒内部产生大量位错,位错滑移引起晶粒内部应变集中增强;变形量由0%增加至30%,晶界应变集中程度因子先增大后减小,变形量为14%时晶界应变集中程度因子最大。利用Ludwigson模型回归拟合了不同变形条件下的真应力-真应变曲线,随变形量的增加,材料的加工硬化程度提高,加工硬化速率减小,发生单滑移向多滑移转变的临界应变减小。     

AE42合金的抗压入蠕变性能

采用自制实验装置对Mg-Al-2RE(AE42)合金进行压入蠕变实验,利用带能谱(EDS)的扫描电镜(SEM)和X射线衍射(XRD)分析合金蠕变前后的组织和成分的演化.结果表明:随温度或应力的增加,AE42合金的压入蠕变速率和第一阶段的蠕变量逐渐增加;合金在压入状态下的蠕变应力指数和蠕变激活能的均值分别为3.06和72.4 kJ/mol;压入条件下AE42合金的稳态蠕变速率由晶界扩散主导的位错粘滞性滑移控制;铸态AE42合金由α-Mg基体、针状Al11La3和少量颗粒状Al2La组成;固溶处理8 h后,合金中的β-Mg17Al12相溶入α-Mg基体,合金的硬度上升;固溶24 h后,晶粒得到粗化,合金的硬度和抗蠕变性能均下降;固溶处理后再人工时效24 h,晶粒略有细化,但大量β-Mg17Al12相沿晶界不连续析出,合金的硬度和抗蠕变性能进一步下降.     

单道次轧制变形对Hastelloy C-276合金晶界特征分布的影响

采用电子背散射衍射(EBSD)技术研究了固溶处理的Hastelloy C-276合金经2.5%~90%变形后在1150℃退火15min的晶界特征分布(GBCD)。结果表明,在5%变形条件下,总的特殊晶界比例最高为67.1%,其中特殊晶界主要是Σ3晶界,Σ9和Σ27晶界比例较低。当变形量小于15%时,晶粒组织处于回复或部分再结晶,晶粒组织粗大,特殊晶界比例随变形量变化较大。在此阶段,回复或部分再结晶有利于晶界的迁移,从而产生更多特殊晶界。当变形量大于15%后,随变形的增加,晶粒组织细小,特殊晶界比例在50%左右。这是由于晶粒发生完全再结晶后,大角度晶界增多,不利于特殊晶界的形成。因而,Hastelloy C-276合金晶界特征分布优化变形范围应小于15%,更有利于特殊晶界的产生和分布。     

GH2132与42CrMo内燃机车增压器摩擦焊

在试验基础上，探讨高温合金ＧＨ２１３２与合金调质钢４２ＣｒＭｏ摩擦焊接头的冶金特点，研究接头组织与性能的关系，为焊接工艺参数的优化提供了理论依据，机车运行结果表明，摩擦焊接的涡轮转子性能可靠，行程已远远超过铁道部规定的指标。     

冷拉伸预变形及热处理对Hastelloy C-276合金晶界特征的影响

对Hastelloy C-276合金分别进行2%、6%、14%、22%、30%和54%冷拉伸预形变后经1100 ℃×15 min等温退火并水冷,采用EBSD技术分析变形量对其合金晶界特征分布和晶粒尺寸的影响。结果表明,随着变形量的增加,总的特殊晶界比例呈先下降后上升最后下降的趋势。当变形量为14%时,总的特殊晶界比例出现峰值点,达到了64.8%,同时Σ1晶界比例出现拐点,呈下降趋势,变形储存能得以释放,有利于特殊晶界的产生。此时,晶粒组织处于再结晶初始阶段。但大变形条件下的退火并不利于特殊晶界比例的提高。随着晶粒尺寸的增加,退火孪晶密度降低,选择适当的晶粒尺寸有利于晶界特征分布优化。