Walzplattierung WStE 355/NiMo 28 (Alloy B-2): Eine preisgünstige Werkstoffkombination für die Chemietechnik

Roll cladding WStE 355/NiMo 28 (Alloy B-2): A low cost alternative material combination for the chemical industry This paper describes the manufacture of rolled clad plates – base metal fine grain structural steel similar to WStE 355, cladding metal nickel alloy NiMo 28. From one plate, subsequently a semi-elliptical head was fabricated. Difficulties had so far been encountered in the manufacture of such roll claddings: Due to heat input during rolling precipitations had occurred in the cladding metal. In order to achieve satisfactory corrosion resistance of the nickel alloy, solution annealing was necessary. This heat treatment resulted in the formation of coarse grain in the base metal, adversely affecting the mechanical properties. A modification of the chemical composition of the base metal and a heat treatment adjusted to the sandwich material made it possible to produce clad plates with fully satisfactory properties. The mechanical and technological properties of the base metal met the standard requirements for fine grain structural steel WStE 355. The corrosion resistance characteristics of the cladding metal were practically unchanged in the solution-annealed condition as compared to the nickel alloy. Welded joints were made to test the weldability of the sandwich material. Testing of the welded joints has yielded satisfactory results. A comparison of manufacturing costs of an agitator tank – capacity 6.3 m³, operating temperature 300°C, working pressure 2.5 bar (absolute value) – showed that total costs were reduced by 15%, if the tank was made of clad plate as compared with a tank made of Alloy B-2 solid plate.     

Sprengplattierte Stahlbleche mit Auflagewerkstoffen aus NE-Metallen und hochkorrosionsbeständigen Werkstoffen für Apparate und Anlagen der Chemischen Industrie

Explosion clad steel sheet with claddings of non-ferrous metals and materials with high corrosion resistance for apparatus and equipment in chemical industries The author reviews various types of clad metal sheet with steel as the base metal. Steel/Ti combinations are used for autoclaves; comparable properties are obtained from steel/Zr combinations. Steel/Ta combinations are suitable for reactors requiring a high corrosion resistance at elevated temperatures. The combination steel/ferritic steel can be used to obtain surfaces resistant to intercrystalline corrosion. The same is true with steel/bickel alloy and steel/nickel combinations. The steel/Cu combination is characterized by high shear strength. In all the cases mentioned it is indispensable, however, to take into account the welding behaviour because it is advisable as far as possible to avoid interdiffusion between the metallic phases.     

Effect of delta ferrite content on the corrosion resistance of type 316 clad metals

Austenitic claddings of type 316 were obtained by SMAW (Shielded Metal Arc Welding) and SAW (Submerged Arc Welding) processes, using type 316 L electrodes on low carbon boiler steel (SA 515 Gr 60) with type 309 L as a barrier layer deposited by the SAW process. Welding heat input was changed in order to obtain different ferrite contents in the cladding. The clad samples were post-weld heat treated at 650°C for 50 and 200 h. The top layer of the cladding was removed and the specimens were then subjected to intergranular corrosion tests (ASTM A-262-75, practices A, B, C and E, viz. 10% oxalic acid electrolytic etch; ferric sulfate ?50% sulfuric acid; 65% nitric acid and copper-copper sulfate ?16% sulfuric acid tests) and controlled potential etching test. The study indicated that the ferrite content of the cladding decreases with increasing current. Ferrite transformed after PWHT (post weld heat treatment) was relatively more in claddings obtained with low heat input and containing high ferrite content in the as-clad condition. PWHT led to brittle fracture of high ferrite claddings (above 10 FN). The corrosion attack of ferrite was found to depend on environment. 65% nitric acid attacked ferrite preferentially, whereas in acid-ferric sulfate, ferrite was intact and austenite was attacked. No sample exhibited susceptibility to intergranular corrosion in the as-clad or PWHT conditions in the copper-copper sulfate ?16% acid test. However, PWHT specimens with low ferrite contents (3.55 FN) exhibited grain boundary precipitation at the interface of two adjacent layers. In general, ferrite was found to be beneficial in controlling corrosion rates of clad metals after PWHT. Heat input, within the range studied, did not affect the corrosion rates significantly.     

Analysis of microstructure and wear strength of hard facing used by the sugar and alcohol industry

The sugar and alcohol sector has seen huge growth in recent years in Brazil; however, maintenance in this industry comes at a high cost due to loss of metal from the equipment via wear mechanisms. The objective of this work is to evaluate the abrasive wear resistance and the microstructure of hard claddings deposited in a single layer. Four types of consumables are used in the sugar and alcohol industry: a clad electrode of FeCrC alloy, 4.0 mm of diameter and three self-shielded tubular wires, all 1.6 mm in diameter, of FeCrC, FeCrCNb and FeCrCTiMo alloys. The base metal used was SAE1020 steel. The welds with the tubular wires were produced in short circuit transfer mode, with the same welding current and voltage values. For the wear test a rubber wheel was used, in accordance with ASTM standard G65-91. The wear test pieces were removed from the central region of the test plates, and from the same region two groups of samples were removed for microstructural analysis (under an optical microscope). The results of the tests with the rubber wheel showed that the FeCrCNb alloy had the highest wear resistance, followed by the clad electrode, and the FeCrCMoTi alloy and FeCrC alloy had the worst performance. The FeCrC alloy (for both the clad electrode and for the tubular wire) showed a microstructure formed by M7C3 primary carbonates distributed in a matrix of lower hardness; the alloy containing Nb showed a similar microstructure as well as the presence of NbC carbonates; in turn, the alloy with Ti and Mo added revealed the presence of large primary titanium carbonates.     

Long term corrosion behavior of clad aluminum materials under different atmospheric conditions

Aluminum materials roll‐plated on both sides are combinations of metals, which consist of clad layers on a core. To document the long term behavior of roof profiles of Alclad 3004 after long term exposure of about 40 years, evaluations were made at three locations in Germany with different climatic conditions. Locations with typical rural‐urban, coastal‐urban, and industrial climates were selected. The corrosion progress as a function of time and climatic type could be characterized by cross‐sections of roof specimens. To interpret the protective mechanism of the clad layer, the corrosion behavior of Alclad 6025 was characterized by electrochemical investigations. The results show that the passive clad material easily undergoes pitting in media containing specific amounts of chlorides. In case of contact of both cladding and core with an electrolyte the core alloy was protected because of the pitting corrosion of the cladding. This guarantees long‐time corrosion protection of constructions like facades or roofs under different atmospheric conditions.     

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.     

Dilution and Ferrite Number Prediction in Pulsed Current Cladding of Super-Duplex Stainless Steel Using RSM

Super-duplex stainless steels have an excellent combination of mechanical properties and corrosion resistance at relatively low temperatures and can be used as a coating to improve the corrosion and wear resistance of low carbon and low alloy steels. Such coatings can be produced using weld cladding. In this study, pulsed current gas tungsten arc cladding process was utilized to deposit super-duplex stainless steel on high strength low alloy steel substrates. In such claddings, it is essential to understand how the dilution affects the composition and ferrite number of super-duplex stainless steel layer in order to be able to estimate its corrosion resistance and mechanical properties. In the current study, the effect of pulsed current gas tungsten arc cladding process parameters on the dilution and ferrite number of super-duplex stainless steel clad layer was investigated by applying response surface methodology. The validity of the proposed models was investigated by using quadratic regression models and analysis of variance. The results showed an inverse relationship between dilution and ferrite number. They also showed that increasing the heat input decreases the ferrite number. The proposed mathematical models are useful for predicting and controlling the ferrite number within an acceptable range for super-duplex stainless steel cladding.     

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.     

核阀密封面激光熔覆层耐蚀性能研究

采用5kW横流CO2激光器对1Cr18Ni9Ti核阀密封面进行了钻基合金激光熔覆处理，测定了激光熔覆层的耐腐蚀性能，并将其微观结构及质量、耐腐蚀性能与等离子喷焊处理的同种试件进行了对比分析，结果表明：激光熔覆层具有优良的综合抗腐蚀性能，具有组织细密、晶粒度高、硬度高与稀释率低的特点。在此基础上对激光熔覆层的耐腐蚀性能进行了分析探讨。     

不锈钢表面激光熔覆层耐腐蚀研究

研究了在耐酸不锈钢基体上采用激光熔覆和等离子喷焊两种工艺形成的涂层对耐腐蚀性的影响。使用５ｋＷ横流ＣＯ２激光器对预置于基体上的Ｃｏ基自熔合金粉末进行单道或多道扫描。得到的熔层与等离子焊层对比,激光熔层缺陷率低,成品率高。其组织细密均匀,晶粒细小,成分稀释率更小,对其体热影响小,熔层硬度与强韧性更高。性能试验证明,激光熔层具有更高的耐腐蚀性能。     

激光熔覆Ni-Cr-B-Si耐热疲劳合金的组织与性能

在H13压铸模具钢表面进行了激光熔覆Ni-Cr-B-Si耐热疲劳合金的试验研究,利用金相显微镜、扫描电镜、显微维氏硬度计等仪器检测了熔覆层的组织和性能。结果表明,激光熔覆可以得到晶粒超细化、硬度高,与基体结合牢固的表面熔覆层。熔覆层组织为Ni基多元固溶体+碳化物(碳化铬、碳化钨、渗碳体),熔覆层平均硬度约732 HV0.2,平均厚度1.5 mm,与基体相比,其耐热疲劳性能提高112%,可显著提高合金压铸模的使用寿命。     

多元硬质合金覆层材料力学性能的研究

为提高钢材表面的耐磨损和耐腐蚀能力,以Mo粉、Fe-B合金粉和Fe粉为基本原料,加入WC、Cr3C2、TiC等碳化物硬质相和C、Ni、Cr等合金元素,采用真空液相烧结工艺,在Q235钢基体上制备多元硬质合金覆层材料.对覆层材料进行了洛氏硬度测试及弯曲强度测试,结果表明:CW系覆层材料的硬度达到HRA84.8,是Q235钢基体硬度的2.3倍;CW系覆层材料的弯曲强度值达到1175.52MPa,是Q235钢基体弯曲强度的1.4倍;掺加碳化物硬质相显著提高了Mo2FeB2硬质合金覆层材料的硬度和弯曲强度.利用扫描电镜观察了硬质合金覆层以及覆层-钢基体界面的微观组织结构,发现硬质合金覆层内部组织结构致密,覆层与钢基体之间形成了具有一定厚度的过渡层.     

Tribological characteristics of WC-based claddings using a ball-cratering method

Tungsten carbide-based thick coatings are used as wear resistant claddings or surface overlays in industrial applications to counter erosive and/or abrasive wear problems. Three-body abrasive wear behaviour of infiltration brazed tungsten carbide (WC) claddings was investigated using a ball-cratering method, a version with a free ball, with slurry containing 150–300 μm silica sand particles. Three WC claddings tested had different volume fractions and size distribution of carbides that resulted in their different bulk hardness and the matrix was a Ni–Cr based alloy. It was found that the wear rates of all WC claddings were almost constant with testing time or distance travelled by a rotating ball. The wear rates were independent of the slurry delivery rate and did not increase with increasing rotating ball roughness. The wear rates were affected by the material characteristics of WC claddings such as the volume fraction of carbides, directly related to bulk hardness, and carbide size distribution. SEM examination found that three-body rolling wear was a dominating wear mechanism. The softer matrix was worn out preferentially, leaving behind protruding and weakly-supported carbides. Small solid carbides were then dislodged and larger cemented WC/Co carbides were gradually worn out by a combination of microcracking and attrition.The abrasive characteristics of WC claddings in the ball-cratering tests were then compared to the characteristics of nominally identical materials in the standard ASTM G65 and G76 tests, as reported in the literature, and similarities and differences found are reported. Also, the in-field wear mechanisms found in the WC cladding were compared to the mechanisms observed in the ball-cratering tests.     

Einfluß einer Eisenaufmischung auf das Korrosionsverhalten von NiCu30 Fe-Stahlplattierungen

The influence of iron pick-up on the corrosion properties of NiCu30Fe/steel clad materials The influence of iron pick-up on the corrosion properties of overlay and butt weldings of NiCu30Fe/steel cald materials was investigated by electrochemical tests in aerated artificial sea water (ASTM Standard D 1141-75) at 25, 50 und 80°C and by exposure to sea water in a sea water test rig on Helgoland. NiCu30Fe plates with defined Fe contents between 0% and 14% were used for comparison. On the Fe being distributed homogeneously, no negative influence of the iron on the pitting resistance was noted in aerated artifical sea water of 25°C up to an Fe content of 10%. The pitting resistance increases with rising temperature (50 and 80°C) and the Fe influence increases slightly. On exposure to sea water on Helgoland, the corrosion in the subtidal zone is mainly caused by marine growth resulting in the formation of shallow pits. In the tidal zone, Fe contents of more than 6.7% cause rust pittings at very low integral corrosion rates (≤0.002 mm/a). With integral Fe contents of between 0.5% and 3% in the final pass, the overlay welds have the same good corrosion resistance properties as commercial NiCu30Fe plate material. The compound butt welds exhibit slight pitting in the weld metal and the heat-affected zone which cannot be conclusively attributed to Fe pick-up but is rather due to the different free corrosion potentials of the NiCu30Mn(Ti) weld metal and the NiCu30Fe cladding material. In the tidal zone which is the preferential application of NiCu30Fe corrosion rates are less than 0.01 mm/a for all specimens welded by different welding methods. Iron contents of up to 8% which can be met by all welding methods when welded in two layers have no negative effect on the corrosion properties.     

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.     

WC颗粒增强铜基合金覆层用钎料的研究

研制了一种新型钢用WC颗粒增强铜基合金覆层用的CuMnNiCr多元铜基钎料,对该钎料的熔化特性、钎料组织、钎焊工艺及力学性能进行了研究,并通过优化的钎焊表面合金化工艺,在普通铸钢件表层制得了WC颗粒增强铜基合金耐磨覆层.研究结果表明,与普通的CuZnNi、CuMnNi合金钎料及NiCrBSi高温自熔合金钎料比较,CuMnNiCr多元合金钎料由于多种强化机制而具有优良的综合力学性能.此外,该钎料还具有优异的钎焊冶金特性、致密的冶金结合界面以及较高的界面结合强度.使用该钎料制备的复合覆层具有良好的综合性能.SEM,EDS及XRD分析表明:该复合覆层与钢母体结合牢固;覆层内合金基体与WC颗粒形成了冶金结合,WC的体积分数可达54%,复合覆层组织由α-Cu固溶体基体、α-Cr与MnNi弥散硬化相及WC硬质相组成.磨损实验证明,该覆层的耐磨性远优于30MnSiTi马氏体低合金钢.     

Einfluss der Halbzeugform auf die Korrosionsbeständigkeit hochlegierter Ni‐Cr‐Mo‐Werkstoffe

Effect of semi‐finished products on the corrosion resistance of high‐alloyed Ni‐Cr‐Mo materials The corrosion resistance of different semi‐finished products of six superaustenitic steels and nickel based alloys in the condition of delivery was investigated in some typical standard corrosion tests. The resistance of sheets, plates, strips, seamless tubes and welded tubes to intercrystalline corrosion was tested according to ASTM G 28 methods A and B, as well the resistance to pitting corrosion according to ASTM G 48 method C. The nickel based alloys 625, C‐276 and alloy 59 are resistant to the FeCl₃‐test according to ASTM G 48 method C and therefore a differentiation of these types in regard to their localized corrosion resistance was achieved only in the more aggressive ‘Green‐Death’‐solution. The laboratory experiments confirmed that the corrosion resistance is identical for all semi‐finished products and that it shows only a slight dependence of the surface condition of the materials tested. Additionally, some typical industrial and practical applications of the six high performance materials are presented to demonstrate the excellent corrosion resistance in the manufactured condition.     

等离子弧金属表面熔覆处理的研究

在钢的表面上用Ni基合金粉末进行等离子弧熔覆处理。试验结果表明 ,用优化后的等离子弧熔覆工艺可以在钢的表面获得致密、结合牢固和零稀释率的熔覆层。因此等离子弧熔覆处理是一种有发展前途、环境友好的金属表面改性处理技术     

DSS2205轧制与爆炸复合板复层组织与性能分析

采用实验室化学浸泡、电化学腐蚀试验及维氏硬度测量技术研究了DSS2205爆炸及热轧复合板复层性能,利用金相显微镜、透射电镜分析了复层组织,并与复合前的DSS2205进行了对比分析.结果表明:相比复合前的DSS2205不锈钢,轧制和爆炸复合板复层腐蚀性能略有下降,硬度增加,但轧制复合板复层腐蚀性能优于爆炸复合板复层;轧制...     

铝-钢爆炸复合板腐蚀性能

采用爆炸焊接方法获得了三种不同的铝-钢爆炸复合板,通过测试其在人造海水中的腐蚀速率,对其腐蚀性能及特征进行了讨论。结果表明:铝-钢爆炸复合板在人造海水中主要发生电偶腐蚀,钢基板腐蚀较轻,铝复板加速腐蚀并且表面形成许多点蚀坑。以不锈钢为基板的铝-钢复合板的腐蚀速率最大。随着时间的延长,三种复合板的腐蚀速率逐渐变小并趋于稳定。