Corrosion Resistance Of Welds Research Articles

Study of the corrosion resistance of high chromium white cast iron welds in the presence of NaOH (30% w/w)

– In the mining industry, specifically in bauxite processing, adverse working conditions demand high mechanical and chemical resistance. For such conditions, the choice of potentially resistant materials, such as high chromium white cast iron (HCr-CWI), is necessary. However, presently, there is no effective recovery of equipment made with HCr-CWI, primarily due to the machining difficulties encountered during the repair process. An alternative recovery method is being developed by the Laboratory of Metallic Materials Characterization at UFPA – LCAM, using electric arc welding with two filler metals: the ER307L stainless steel wire andsa high Mn value wire. Within this context, this study aims to investigate the corrosion resistance of the welded joint obtained with these two filler metals. The base metal (HCr-CWI) was analysed as a reference, alongside the metals generated by the welded joints, ER307L and high Mn. The samples underwent tests involving optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and electrochemical tests for corrosion potential, polarization, and impedance. It was observed that the samples exhibited a similar matrix-carbide structure but with different organization and volumes. However, the electrochemical behaviour in terms of corrosion potential, polarization, and impedance was similar, with very close resultant values: 50 V; 3.53 μA; 0.18 kOhms, respectively. This was supported by the corrosion rate of 0.4mmpy and explained by calculations of Cr and Ni volume, which showed inverse concentration magnitudes among the samples.

Effect of Ni-based Fillers on Corrosion Resistance of Heat Affected Zone of Super Austenitic Stainless Steel (UNS S31254) Welded by GTAW

The effect of Ni-based fillers on corrosion resistance of welded super austenitic stainless steel (SASS) was examined. The use of Ni-based fillers for gas tungsten arc welded SASS leads to the formation of fine Cr-Mo enriched phase in its weld unmixed zone, which makes it more susceptible to the localized corrosion. The metallographic observations showed that the pits were initiated around the fine Cr-Mo enriched phase precipitated in unmixed zone, and they were propagated along the base metal. The degree of corrosion damage among the welded samples using the three types of Ni-based fillers (Inconel 625, Inconel 622, Hastelloy 276) increased with the Mo contents in the fillers applied. The higher the Mo contents in the fillers, the higher the size/number ratio of Cr-Mo enriched phase with higher concentration of Mo, precipitated in unmixed zone. Based on the results, it is proposed that the Mo contents in Ni-based high alloyed fillers can have a great effect on the precipitation behavior of Cr-Mo enriched phase in unmixed zone, causing deterioration of corrosion resistance of SASS welds. Therefore, the Mo content in the filler should be optimized with the content similar to that of the base metal so as not to susceptible to localized corrosion.

Influence of assembly procesS condition of A gantry crane on the corrosion resistance of welds

The article presents an analysis of the manufacturing process of gantry crane elements in the unit production regime. Gantry cranes are one of the most important heavy-duty mechanical components designed for lifting and loading heavy and bulky loads. In the analyzed case, the assembly of large-size elements in the form of a welding process was carried out outside. Therefore, there was a problem with the corrosion resistance of the elements produced in this way. In this article, special attention is paid to the performance of welded joints of such large elements and their disadvantages related to the conditions of the assembly process. These joints were made on the basis of typical, low-carbon structural steel (grade S355J2, steel with the number 1.0562) and Nickel alloy (Alloy 59, X2CrNiMoCuN22-5-3, steel with the number 2.4605) using the metal electrode. The weldability of investigated joints was assessed. The aim of the article is to analyze the influence of assembly conditions and subsequent corrosion protection of joints on their corrosion resistance under operating conditions. Appropriate tests have been carried out for this purpose. The tests showed the negative influence of external conditions on the corrosion resistance of the entire gantry crane structure.

Mechanical, microstructure, and hot corrosion investigations on P22/P91 dissimilar tungsten inert gas weld

The P22/P91 dissimilar weld increasingly used in supercritical power plan boilers calls for experimental investigations on its properties for enhanced performance in high-temperature service conditions. This study investigates the weld joint between P22/P91 steel using tungsten inert gas process employing a P22 matching filler metal. The fabricated weld has been characterized for mechanical properties of tensile strength and microhardness. The microstructural examination has been carried out in the weld region, transition zones, and base metals. The weld was exposed to a temperature of 700 °C in the environment of molten salt (50% Na2SO4 + 50% NaCl) to quantify the effect of high-temperature corrosion at its sight of application. Furthermore, the welds were also shot-peened and its effect on corrosion properties has been examined. The corroded specimens were examined using X-ray diffraction and scanning electron microscope to analyze the oxide scale produced upon exposure to high temperature in a controlled environment. The P22 base metal was found to oxidize more severely as compared to the weld fusion zone. Shot peening improves the corrosion resistance of weld by 7.56%. The results of this study comprehensively cover multiple aspects of weld integrity as per the service conditions, with its results having significant application in the power plant industry.

A Comparison between Tungsten Inert Gas Welded Joints Welded by Commercial ER5183 Filler and Al–Mg–Zn–Sc–Zr–Mn Filler on Microstructure and Properties in 7075-T651 Aluminum Alloys

A 7075-T651 aluminum alloy was successfully welded by tungsten inert gas welding using commercial ER5183 wire and Al–5Mg–1Zn–0.3Sc–0.15Zr welding wire containing different contents of Mn. The microstructure, corresponding mechanical properties, and the corrosion behavior of the welded joint were investigated by microscopy methods, tensile tests, and corrosion tests. The results revealed that Al3(Sc,Zr) particles were distributed in a small amount in the welds and refined the primary α-Al grain. The addition of Mn gives a strong interaction of improving fracture strength, micro-hardness, and corrosion resistance reducing the harmful influence of iron, as a result, the properties of the welded joint were enhanced. And the increase of Mn content improves the tensile strength and hardness of welds, which could be attributed to the refinement of eutectic T phase by Mn. Potentiodynamic polarization tests revealed that the corrosion resistance of welds increased with the increase of Mn content. Compared with the welded joint using commercial filler, the welded joint with Al–Mg–Zn–Sc–Zr–Mn filler exhibited a higher resistance to stress corrosion cracking (SCC). In conclusion, Al–Mg–Zn–Sc–Zr–Mn filler can be using for welding 7XXX aluminum alloys.

Experimental study on corrosion resistance of coiled tubing welds in high temperature and pressure environment.

Coiled tubing (CT) has been widely used for oil and gas exploitation, however corrosion of CT under high pressure and high temperature (HPHT) environment was often reported, also corrosion induced failures of CT welds were often observed to occur during service. Corrosion related behaviors of CT welds are not clear. Therefore, a study of the corrosion resistance of CT welds under HPHT environment is carried out. In order to efficiently evaluate the corrosion resistance of welds, some test samples were obtained by linear cutting out of a CT110 in service on the site. The water samples from gas field were used as the test reagent to simulate the actual corrosive medium. Based on the results of weight loss test under HPHT corrosive environment and tensile test under room conditions, the corrosion sensitivities of the welding seam and base material under various temperatures and partial pressures of CO2 as well as the mechanical properties of the corroded CT were compared and evaluated quantitatively, the corrosion morphologies and material products of the test samples were analyzed by scanning electron microscope (SEM). The test results showed that the corrosion rates of the welding seam in a HPHT caldron were 1.7, 2.0 and 1.2 times of the base metal’s when the total pressure is 4MPa, and the temperature is 30°C, 60°C and 90°C, respectively. The corrosion rates of the welding seam is 2.0, 2.1 and 2.0 times of the base metal’s when the partial pressure of CO2 is 0.1MPa, 0.2MPa and 0.3MPa, respectively. The yield strength of the weld seam after corrosion test was found to be reduced by 4.8% (the yield strength of the base metal was reduced by 4.0%) and its tensile strength was reduced by 8.2% (the base metal was reduced by 7.1%). This indicates that CT weld seam is more susceptible to corrosion than CT base material under service condition.

Experimental investigation of structural integrity behavior of High strength low alloy steel – Study of mechanical, microstructural and corrosion behavior of Submerged arc welding weldments

The present study aims at investigating the effect of submerged arc welding fluxes for enhanced corrosion resistance of structural steel welds. By varying the basicity index of submerged arc welding fluxes the corrosion resistance and mechanical properties of weld metal such as tensile strength, impact strength, microhardness in submerged arc weldments were evaluated. The result shows that with the increase in bascity index tensile strength of weld specimen reduced while impact strength and microhardness value increased. Maximum microhardness (288 HV) was observed for flux 2 while base metal show minimum microhardness value (205 HV). Flux 5 gives maximum impact strength (94.17 J) as compared to the base metal (80 J). This is due to the reduced content of oxygen in weld metal which increases the weld metal impact toughness. Corrosion resistance of weld specimen increased as compared to the base metal. Ductile fracture mode and shear lip or tears were observed in the weld zone. Shear dimples and shear lips were more severe in base metal as well as weld metal impact specimens due to the rapid effect of external forces on the impact test. The banded microstructure of delta ferrite and austenite was observed in the base metal. Fine grains of ferrite and pearlite at the center and edges were present in the weld zone.

Relationship Between Corrosion Resistance and Microstructure Characteristic of Single-Pass Laser-Arc Hybrid Welded Stainless Clad Steel Plate

Superior weld corrosion resistance to base metal (BM) of stainless clad steel plate (SCSP) was achieved by laser-arc hybrid welding with only one pass. Under optimized parameters, the charge transfer resistance of the weld reached 2.3 times higher than the BM, and the corrosion current density decreased to 70 pct of the BM. Considering the inhomogeneity caused by dendrites, an equivalent Cr content, i.e., [Cr]E, was proposed to establish a new relationship between the corrosion resistance and the microstructure characteristic of the SCSP hybrid weld. It suggests better weld corrosion resistance than the BM is obtained when the [Cr]E ≥ 15.5 pct. The results would be suitable to predict the corrosion resistance of the SCSP weld, and promote its industrial application.

Microstructures and properties of single-pass laser-arc hybrid welded stainless clad steel plate

The effects of wire Cr content on the microstructures and properties of single-pass laser-arc hybrid welded stainless clad steel plate (SCSP) were studied. Increasing Cr content strengthened the weld corrosion resistance, but it increased the average grain size of fusion zone (FZ), deteriorated the weld microstructure uniformity, and weakened the weld mechanical property. The variations of the weld properties were closely related to the microstructure changes. The solidification mode and microstructure transformation mechanism of the SCSP hybrid weld were clarified based on the quantitative calculation of the Cr and Ni equivalent contents (Creq and Nieq) after the mixing of the wire and base metal. The calculated ratio of the Creq and Nieq (θ) could effectively predict the solidification mode and microstructure of the SCSP weld, and then indicate its properties. The skeletal and acicular ferrites formed in the FZ when the θ was larger than 1.35, which benefited to strengthen the SCSP weld.

Studies on Fusion Welding of High Nitrogen Stainless Steel: Microstructure, Mechanical and corrosion Behaviour

An attempt has been made in the present investigation to weld high nitrogen steel of 5mm thick plates using various process i.e., shielded metal arc welding (SMAW), gas tungsten arc welding (GTAW) and autogenous electron beam welding (EBW) process. Present work is aimed at studying the microstructural changes and its effects on mechanical properties and corrosion resistance. Microstructure is characterized by optical, scanning electron microscopy and electron back scattered diffraction technique. Vickers hardness, tensile properties, impact toughness and face bend ductility testing of the welds was carried out. Pitting corrosion resistance of welds was determined using potentio-dynamic polarization testing in 3.5%NaCl solution. Results of the present investigation established that SMA welds made using Cr-Mn-N electrode were observed to have a austenite dendritic grain structure in the weld metal and is having poor mechanical properties but good corrosion resistance. GTA welds made using 18Ni (MDN 250) filler wire were observed to have a reverted austenite in martensite matrix of the weld metal and formation of unmixed zone at the fusion boundary which resulted in better mechanical properties and poor corrosion resistance. Fine grains and uniform distribution of delta ferrite in the austenite matrix and narrow width of weld zone are observed in autogeneous electron beam welds. A good combination of mechanical properties and corrosion resistance was achieved for electron beam welds of high nitrogen steel when compared to SMA and GTA welds.

Effects of alloying element on weld characterization of laser-arc hybrid welding of pure copper

Effects of alloying elements of Si and Sn on weld characterizations of laser-arc hybrid welded pure copper (Cu) with thickness of 2 mm was studied in detail by using different wires. The weld microstructure was analyzed, and the mechanical properties (micro-hardness and tensile property), conductivity and corrosion resistance were tested. The results showed that the alloying elements benefit the growth of column grains within weld fusion zone (FZ), increase the ultimate tensile strength (UTS) of the FZ and weld corrosion resistance, and decrease weld conductivity. The mechanisms were discussed according to the results.

Effects of laser-arc distance on corrosion behavior of single-pass hybrid welded stainless clad steel plate

Single pass laser-arc hybrid welding of stainless clad steel plate was first carried out to develop alternatives to multi-pass welding with low efficient or single pass welding with poor corrosion resistance. The results demonstrated that the weld corrosion resistance increased with the increase of laser-arc distance (DLA), and the corrosion morphologies changed from big and deep ‘nail’ pits to small and shallow hemispherical pits. The weld with nearly equal corrosion resistance to the base metal (BM) could be obtained at the DLA of 9mm, where the charge transfer resistance increased to 89% of the BM and the corrosion current density decreased by ten times to close to the BM, only 0.13μA·cm−2 lower. The corrosion resistance improvement had a good agreement with the microstructure homogenization and the increase of Cr content. The microstructure formation was discussed by the molten pool behavior and the laser-arc interaction. The corrosion resistance improvement was explained by the formation and damage mechanism of the passive film.

Технология сварки алюминиевого деформируемого сплава 1151

The results of the investigations of susceptibility to hot cracks formation at welding of alloy 1151 in comparison with alloys 1201 and 1460 are shown. The character of alloy 1151 is a possibility of hot crack propagation both through a metal seam and through the area of a seam fusion with basic metal. The durability of welds of alloy 1151 carried out by fuse welding and friction welding with blending exceeds the durability of alloys 1201 and 1460. Corrosion resistance of welds of alloy 1151 exceeds considerably the corrosion resistance of compositions of alloy 1201.

Insights into the corrosion perforation of UNS S32205 duplex stainless steel weld in gas transportation pipelines

Microstructure and pitting corrosion resistance of UNS S32205 DSS weld were systematically studied, and its failure causes were analyzed carefully. The results showed the uneven metallographic microstructures with majority of austenite in the HAZ and then the significantly reduced pitting corrosion resistance of the weld. Furthermore, large potential difference between the both sides of the insulation joint and high salinity of the formation water in the pipeline make the leakage current preferably flow out from the weld and enter the transmission fluid, so localized corrosion happens at the inner surface of the weld and leads to the corrosion perforation eventually.

侧吹气体对奥氏体不锈钢激光焊缝组织和耐腐蚀性能的影响

侧吹气体对奥氏体不锈钢激光焊缝组织和耐腐蚀性能的影响

Metallographic investigation and corrosion resistance of welds of ferritic stainless steels

Metallographic investigation and corrosion resistance of welds of ferritic stainless steels

Corrosion Resistance and Mechanical Properties of TIG and A-TIG Welded Joints of Lean Duplex Stainless Steel S82441 / 1.4662

Abstract This paper presents results of pitting corrosion resistance of TIG (autogenous and with filler metal) and A-TIG welded lean duplex stainless steel S82441/1.4662 evaluated according to ASTM G48 method, where autogenous TIG welding process was applied using different amounts of heat input and shielding gases like pure Ar and Ar+N2 and Ar+He mixtures. The results of pitting corrosion resistance of the welded joints of lean duplex stainless steel S82441 were studied in as weld conditions and after different mechanical surface finish treatments. The results of the critical pitting temperature (CPT) determined according to ASTM G48 at temperatures of 15, 25 and 35°C were presented. Three different surface treatment after welding were applied: etching, milling, brushing + etching. The influence of post weld surface treatment was studied in respect to the pitting corrosion resistance, basing on CPT temperature. Research on TIG welding of lean duplex stainless steel S82441/1.4662 showed a clear influence of the applied shielding gas mixtures, where the addition of 5 to 15% N2 to Ar virtually no effect on the level of resistance to pitting corrosion, only 5% N2 addition has a positive effect, while use of a mixture of 50% Ar + 50% He compared with welding at 100% Ar atmosphere, can significantly reduce the resistance to pitting corrosion. Definite good results were obtained during TIG welding with the participation of activation flux (A-TIG). The weld surface of lean duplex stainless S82441/1.4662 obtained in A-TIG welding without the addition of filler metal has a much lower tendency to pitting corrosion than traditional welds made by TIG method. Pitting corrosion resistance of welds made by A-TIG improved with the increase of the heat input in the tested range of welding current 100-200 A. It was also found that the intensity of the occurrence of pitting does not affect the method of cleaning welds after welding, but the mechanical removal of a thin surface layer of metal significantly reduces their intensity.

Effect of activator on mechanical properties and intercrystalline corrosion resistance of austenitic stainless steel weld

5mm thick austenitic stainless steel was welded using an A-TIG welding process with in-house developed activators. The microstructure, mechanical properties, and intergranular corrosion resistance of the weld joint were characterized. The microstructure of conventional TIG and A-TIG welds were all austenite with a small amount of δ-ferrite. The included angle between the fusion line and rolling direction of the conventional TIG and A-TIG welds were nearly 0° and 90°, respectively. The microstructure of the A-TIG weld had more and finer δ-ferrite under conditions of less heat input. Compared with the conventional TIG weld, the tensile strength of the A-TIG weld was enhanced approximately 10%, and the elongation was increased by 30%. The microhardness of the conventional TIG weld was found to be 280HV, and the microhardness of the A-TIG weld was 210HV. The corrosion rates of substrate, conventional TIG and A-TIG welds were measured and found to be 0.056mm/h, 0.110mm/h and 0.065mm/h respectively. The chromic carbide content in the conventional TIG weld was higher than that of the A-TIG weld.

Advanced Gas Tungsten Arc Weld Surfacing Current Status and Application

Abstract Gas Shielded Tungsten Arc Welding (GTAW) – a process well-known providing highest quality weld results joined though by lower performance. Gas Metal Arc Welding (GMAW) is frequently chosen to increase productivity along with broadly accepted quality. Those industry segments, especially required to produce high quality corrosion resistant weld surfacing e.g. applying nickel base filler materials, are regularly in consistent demand to comply with "zero defect" criteria. In this conjunction weld performance limitations are overcome employing advanced 'hot-wire' GTAW systems. This paper, from a Welding Automation perspective, describes the technology of such devices and deals with the current status is this field – namely the application of dual-cathode hot-wire electrode GTAW cladding; considerably broadening achievable limits.

Failure analysis of austenitic stainless steel pipes in amine liquid regeneration unit of a desulfurizer

Failure investigation was carried out on the austenitic stainless steel pipes of an amine liquid purification unit. The authors investigated the causes of the pipe failure by analyzing chemical compositions of materials and corrosion products, observing microstructures, and testing the pitting corrosion resistance of materials. The results showed that the failure was caused by pitting corrosion due to the presence of chlorine ions in the working medium. Another important cause of pitting corrosion was the decrease of corrosion resistance of welds owing to the microstructural changes taken place during welding. A large amount of sulfate ions in the working medium accelerated the pits growth. At the same time, proposals were put forward to the user of the failure pipes.