Corrosion Resistance Of Joints Research Articles

Study on magnetic pulse crimping process for joining large-diameter aluminum alloy tube/magnesium alloy shaft

A structure for joining 6061T6 aluminum alloy tube and AZ31B magnesium alloy shaft via the magnetic pulse crimping process was proposed. The forming process, mechanical properties, failure modes, and corrosion behaviors of the joint were studied. The results showed that the enormous Lorentz force drove the wall of aluminum alloy tube to move towards the groove of magnesium alloy shaft at high velocity, thus realized mechanical locking and formed joint. Through torsion tests, it was found that the mechanical properties of the joint with different process parameters varied. There were two failure modes for joint: torsional separation and torsional crack. Specifically, discharge time, groove angle, and discharge energy for torsional crack were, respectively, 1, 90°, and 28 kJ and 3, 90°, and 25 kJ. The maximum torque was up to 961.99 N·m under discharged twice, 90° groove angle, and 25-kJ discharge energy. Through neutral salt spray corrosion tests, it was found that the maximum torque only decreased by 28.03% after corrosion for 192 h. It indicated that the corrosion resistance of joint was good relatively.

Effect of cooling conditions on corrosion resistance of friction stir welded 2219-T62 aluminum alloy thick plate joint

Abstract Friction stir welding (FSW) with water cooling and air cooling was used to weld 2219-T62 aluminum alloy joints with a thickness of 20 mm. The effect of cooling conditions on the corrosion resistance of joints in 3.5% NaCl solution was investigated using the open circuit potential (OCP), the potentiodynamic polarization, and the corrosion morphology after immersing for different time. And the precipitates distribution was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results reveal that the weld nugget zone (WNZ) owning positive potential, lower corrosion current density and fine and uniform precipitates, is much more difficult to corrode than the heat affected zone (HAZ) and the base metal (BM). Compared with air-cooled joint, the water-cooled joint has better corrosion resistance. In addition, the results of microstructure observation show that the potential, distribution and size of second phase particles determine the corrosion resistance of FSW AA2219 alloy joints in chlorine-contained solution.

Microstructure Evolution Mechanism and Corrosion Behavior of Transient Liquid Phase Bonded 304L Stainless Steel

Transient liquid phase (TLP) bonding of 304L austenitic stainless steel was carried out using MBF-20 interlayer at 1070 °C with different holding times. The effect of bonding time on the microstructure and corrosion resistance of the TLP bonded samples was investigated aiming to obtain the optimal bonding time. The results showed that isothermal solidification was completed within 45 min at 1070 °C and shorter holding times gave rise to the formation of intermetallic compounds at the joint centerline. It was found that the solidification sequence in the joint region is as follows: (1) isothermal solidification of γ solid solution, (2) formation of ternary eutectic of γ + Ni boride + Cr boride, and (3) formation of ternary eutectic of γ + Ni boride + Ni–Si–B compound in the athermally solidified zone. Final stage of the phase formation at the joint centerline was the precipitation of Ni3Si particles in the vicinity of eutectic microconstituents via a solid state transformation. Extensive Cr-rich borides were formed in the diffusion affected zone as a result of B diffusion into the base metal during bonding process. Corrosion behavior of the TLP bonded samples was studied in 3.5% NaCl solution. The joint corrosion resistance was improved with the increase of the bonding time to 30 min and then decreased when the holding time was prolonged.

CORROSION RESISTANCE OF UNS S31803 STAINLESS STEEL WELDED JOINTS

The corrosion resistance of duplex stainless steel welded joints is affected by different parameters such as filler metal chemical composition, heat input, shielding gas composition and post welding heat treatment temperature. In most cases such parameters interact with each other so that it is very difficult to foresee their effect on corrosion resistance of welded joints without specific experimental tests. In this work the best combination of shielding gas composition and post welding heat treatment temperature that guarantees the corrosion resistance of the joint according to ASTM A932, method C, was found. Two shielding gases were tested during welding, Ar (100%) and a mixture of Ar (87%), He (10%) and N (3%), while the solution temperatures were 1050 °C and 1070 °C. It was found that only the samples welded with the mixture of Ar (87%), He (10%), N (3%) as shielding gas and solution heat treated at 1070 °C passed the corrosion test completely.

Effect of grain orientation on the corrosion resistance of FSSW joints made in AZ31B

ABSTRACTLocalised corrosion at the weld periphery of AZ31B friction stir spot welds has been associated with microstructural evolution during the welding process. Several attempts have been made to correlate these changes to the corrosion resistance of a joint; however, the influence of grain reorientation arising from the welding process has been overlooked. Here, the role of grain reorientation during FSSW was investigated using a combination of microcapillary polarisation and analytical microscopy. The influence of changes in grain orientation was shown to have a direct effect on the magnitude of the galvanic couple formed between the stir zone and the base metal.

Evaluation of Corrosion Resistance of Galvanized Steel Sheets Used in Automotive Production

The steel sheets used for the car body production are protected against corrosion by zinc coating. Resistance spot welding is used mainly for joining these sheets, because of its high speed and adaptability for automation in high-rate production. However, resistance spot welding has a negative influence on the corrosion resistance of joints. The paper focuses on the analysis of quality of welds on galvanized steel sheets and their corrosive properties. Tensile test and accelerated corrosion test in corrosive environment were used for evaluation of the welds’ quality. Protective efficiency of zinc coatings for automobile sheets was evaluated as well, based on the determination of their electrochemical characteristics in passivated and non-passivated state, as well as their corrosion resistance in simulated corrosion environments. Two types of DX54D+Z material were used for experiments: non-passivated and passivated with Cr3+.

Effects of Welding Conditions by TIG and Post Weld Heat Treatment in Ductile Cast Iron on the Corrosion Resistance

In this study ductile cast iron plates were welded by tungsten inert gas process (TIG). The objective was to evaluate the effect of filler metals; current welding and post weld heat treatment (PWHT) on the microstructure and corrosion resistance of joints. Metallographic examination of welded plates showed three different zones: fusion zone with a dendritic structure, heat affected zone with mixture of martensite and ledeburite structure and ferritic-pearlitic structure in base metal. Microstructure of welded area changes drastically to acicular ausferrite when the PWHT was applied. Corrosion rates values of 4.5 mpy were obtained in plates welded with E-FeNiCI filler metal and current of 125 and 150 A; this value is approximately half of the ones obtained in the ductile cast iron (10.5 mpy). These results are associated with: a good chemical compatibility of the filler material and ductile cast iron, increases of Ni content, refinement of the structure and a higher dissolution of graphite nodules that mitigate graphitic corrosion mechanism. The PWHT plates showed a slightly decrease in corrosion rates. In particular, plates welded with E-FeNiCI filler material and 125 A of current intensities exhibited the best corrosion resistance (3.75 mpy). This phenomenon can be attributed to homogenization of nickel in the weld bead forming passive layers that increase the corrosion resistance.

Microstructure and Corrosion Resistance of Dissimilar Welded Joints between Duplex Stainless Steel and Austenitic Stainless Steel

The dissimilar metals components of duplex stainless steels are more and more used in engineering fields recently. But the welding of dissimilar metals is more a challenge than that of similar metals. The joints of dissimilar metals between 2205 duplex stainless steel and 304 austenitic stainless steel were produced by tungsten inert gas arc welding (GTAW) with welding wire ER2209 and ER309, respectively. The microstructural characterization of welded joints is systematically analyzed by using optical microscope and X-ray diffractometer. The pitting corrosion resistance of the joints is evaluated by electrochemical test. Results show that the microstructure of joint consists of austenite and ferrite, and no detrimental phases precipitate in the weldment. The biphase ratio of austenite (γ) / ferrite (α) is adequate both in weld metal and heat-affected zone (HAZ), which is advantageous to the performance of welded joints. The weld metals have relatively lower pitting corrosion resistance compared with the 2205 base metal, and the pitting corrosion resistance of the joint produced with ER2209 is better than that of the joint with ER309 in chloride solution.

Investigation of the corrosion behaviour of laser-TIG hybrid welded Mg alloys

The paper presents the corrosion behaviour of the laser–tungsten inert gas welded Mg alloy. The effects of microstructure variations of Mg alloy joint on the corrosion behaviour and reliabilities of joint are investigated. The results demonstrate that the effects of some weld defects and precipitated phases on the corrosion behaviour of weld joint are very little, and corrosion resistance of joint is predominantly influenced by grain refinement or interactions of grain refinement and continued net-shaped β phases. Moreover, the corrosion resistance of weld joints and welding mode (butt and lap joint) keep a close relation, which must not be ignored.

Strength and corrosion resistance of a solder joint in ultrasonic soldering of aluminium using quasi-melting solder

In order to obtain high-strength aluminium butt joints with corrosion resistance, ultrasonic soldering of A1070 rods was conducted using quasi-melting Sn–xZn (x = 23, 40, 82 mass%) hypereutectic alloy. Ultrasonic vibrations were applied at soldering temperatures ranging 220–300°C through A1070 rods without a solder bath. The tensile strength of the solder joints with Sn–23Zn or 40Zn alloy were higher than that of the joint soldered with Sn–9Zn eutectic alloy. The joints soldered with Sn–23Zn or 40Zn alloy showed the same strength as A1070 rods which employed the same heat treatment as the ultrasonic soldering process. The thickness of the hypereutectic solder layer in the joints was thicker than that of the Sn–9Zn solder layer because unmelted α-Zn solid solution should have prevented the solder from being pressed out of the joint gap by the applied pressure during soldering. Tensile tests of the joints after immersion in NaCl aqueous solution revealed that the corrosion resistance of the joints soldered with hypereutectic alloy was higher than that of the joint soldered with Sn–9Zn alloy. It is considered that the improvement was achieved by the thick hypereutectic solder layer which should have reduced the notch effect in the joints.

Improvement of the mechanical characteristics and corrosion resistance of welded joints of maraging steels

We show that the specific character of a structural state of welded joints of Kh11N10M2T steel as a sequence of structural changes in the course of accelerated heating of maraging steels causes a regular inhomogeneity of their mechanical characteristics and low corrosion resistance. We develop a procedure of thermal treatment which guarantees homogeneity of welded joints in strength, plasticity, and toughness. The mechanical characteristics and corrosion resistance of these joints correspond to those of the base metal that is reached due to both removal of interdendritic liquating inhomogeneity of the weld metal and equalization of the structure and phase composition in all zones of a welded joint.

Weldability and corrosion resistance of joints in the stable austenitic 03Kh21N21M4GB steel and 06KhN28MDT alloy

Weldability and corrosion resistance of joints in the stable austenitic 03Kh21N21M4GB steel and 06KhN28MDT alloy