Minimum Corrosion Rate Research Articles

Effect of beam current on microstructure, tensile properties and corrosion behaviour of electron beam welded zircaloy-4 joints

ABSTRACT Butt joints of zircaloy-4 were made using electron beam (EB) welding. The effect of beam current (15–20 mA) on weld zone size, microstructure, porosity, mechanical and corrosion properties has been investigated. Local temperature and cooling rate were estimated, and the average cooling rate increased from 2.4 to 6.3°C ms–1 with a decrease in beam current in the said range. Joints prepared at lower beam current possessed smoother weld surface, narrow weld bead, and fine lamellar type widmanstätten structure in the fusion zone (FZ). The length of the α-Zr lamella (from 105 to 37 µm) and interlamellar space (from 0.8 to 0.3 µm) decreased with a decrease in beam current. The XCT result revealed that porosity increased with an increase in beam current, and large-size micro pores of 180 µm were present in joints prepared at high beam current. The hardness of the welded samples increased by 13–20% than the base metal. The joint prepared with a low beam current possessed higher ductility (29%) and a minimum corrosion rate (0.0085 mmpy in 3.5 wt-% of NaCl solution) than the joint made with a higher beam current.

An Eco-friendly Mangifera indica Leaves Extract Corrosion Inhibitor for Stainless Steel in Acidic Medium

Corrosion of metals and alloys is one of the most frequent problems encountered in chemical and process industries. Inefficient corrosion control measures typically lead to an increased risk of unplanned downtime, huge economic loss, environmental damage, and health and safety hazards. Hence, it is essential to develop environment-friendly and cost-effective corrosion inhibitors over existing toxic anticorrosive agents. The main objective of this work is to examine the efficacy of eco-friendly ethanolic extract of Mangifera indica leaves (MIL) in different concentrations as a green corrosion inhibitor for stainless steel (SS-316L) under an acidic environment. The inhibition efficiency of Mangifera indica leaves extract in 1 M hydrochloric acid (HCl) was evaluated by conventional weight loss method along with adsorption isotherm analysis. Chemical compounds present in leaf extract and changes in surface morphology of SS-316L samples were assessed using Fourier Transform Infrared spectroscopy (FTIR) and Field Emission Scanning Electron Microscopy (FE-SEM) provided with elemental analysis. The results of the weight loss method revealed that the inhibition efficiency increases with increasing MIL extract concentration due to higher surface coverage. The highest inhibition efficiency of almost 63.43% in 14 days and minimum corrosion rate of 0.433 mm per year was obtained for SS-316 L in 1.0 M HCl with 1000 ppm concentration. The adsorption of MIL extract on SS-316L surface followed Freundlich adsorption isotherm, and the obtained value of free Energy of adsorption (ΔG˚ads = – 9.20 kJ.mol-1) indicates the physical adsorption mechanism. The developed regression-based models can predict the corrosion rate as a function of inhibitor concentration and exposure time with good accuracy (>80%). Thus, the present findings demonstrate that Mangifera indica L. leaves extract can suitably be applied as an inexpensive, non-toxic, biodegradable, efficient green corrosion inhibitor for the protection of stainless steel in acidic media.

Investigation of Microstructure, Mechanics, and Corrosion Properties of Ti6Al4V Alloy in Different Solutions

There is a scarcity of research on the characterization of the behaviour of titanium and its alloys in highly corrosive environments. These materials are highly recommended for use in various industries such as aviation, maritime, medical, and chemical, due to their perceived superior corrosion resistance. This research examines the mechanical and corrosion characteristics of Ti6Al4V material when exposed to solutions containing 9% NaCl, 25% HCl, and a mixture of 9% NaCl and 25% HCl. Prior to the corrosion process, the prefabricated Ti6Al4V samples underwent microstructure analysis, hardness assessment, and wear evaluation. The microstructure characterization revealed that the microstructure of the Ti6Al4V alloy is composed of α and modified β phases. The Ti6Al4V sample’s hardness value was determined to be 334.23 HB. The Ti6Al4V sample’s wear rate was determined to be 0.0033 g/Nm, while the friction coefficient was determined to be 0.0326. Corrosion testing was conducted at intervals of 24, 48, 72, 168, and 336 h. Based on the corrosion rate measurements, the sample exhibited the minimum corrosion rate of 1.928519 mg/(dm2·day) in a 9% NaCl environment. The sample with a combination of 9% NaCl and 25% HCl had the maximum corrosion rate, measured at 6.493048 mg per square decimetre per day. The formation of a larger oxide layer in the Ti6Al4V corrosion sample immersed in a 9% NaCl solution serves as a protective barrier on the surface and enhances its resistance to corrosion.

Optimization of Corrosion Behaviour of Blended TiO2 /ZnO Coating on SUS 304 using Taguchi Method

Objectives: To determine the best combination of blends of TiO2 /ZnO coated on SUS for obtaining a minimum corrosion rate. Methods: Different TiO2 /ZnO thin film blends are coated on SUS 304 substrates. The sol-gel dip-coating process is used for coating application. Also, withdrawal rates, calcination temperature, and doping percentage are the parameters used for the study of the anti-corrosion property. L9 array, using the Taguchi method, is applied for the design of the experiment. P.G-Lyte 1.0 model was used for the anticorrosion test. The Potentiosatic polarization method was applied for anti-corrosion testing. Findings: The results show that the percentage of ZnO doping (60%, 40%, and 20%) is the most significant factor in controlling the corrosion of the sample with plate number 1. The withdrawal rate (0.5 mm/sec, 1 mm/sec, and 1.5 mm/sec) has a minimal impact on the corrosion rate of the coated sample. The calcination temperature (300◦C, 400◦C, and 500◦C) has a greater impact than the withdrawal rate. There is a good agreement between the predicted and actual corrosion current. Novelty: Investigation of mechanical properties like corrosion resistance is essential for increasing the durability of automobile components by applying a coating of blends of TiO2 and ZnO with a rare blending combination that was not applied before for the investigation. In this research, efforts are made to reduce the corrosion rate by applying different blends of TiO2 and ZnO. Also, withdrawal rate and calcination temperature are varied in the process which was also not considered in the earlier studies. Keywords: Taguchi method; Corrosion current; Signal to Noise ratio; Coating; Design of experiments

Mechanical, electrochemical corrosion, and high-temperature oxidation properties of stir-cast and heat-treated AZ80 magnesium alloy

This study aims to produce a stir-cast AZ80 magnesium alloy and to correlate the phases and microstructure of the as-cast, T4, and T6 conditions with the alloy's mechanical, corrosion, and oxidation properties. Microstructure was analysed using Field Emission Scanning Electron Microscopy (FE-SEM) with Energy Dispersive Spectroscopy (EDS), Electron Backscatter Diffraction (EBSD), and High-Resolution Transmission Electron Microscopy (HRTEM), and X-ray diffraction (XRD) technique was employed to examine at the alloy’s phases. A Vickers microhardness, tensile, and impact test specimens were meticulously prepared according to ASTM specifications. The electrochemical corrosion was tested in 0.6 M NaCl and 0.05 H2SO4, simulating the salty seawater and low-sulphur air environments. Based on the eutectic temperature of the Mg-Al alloy system, which is 437 ℃, the high-temperature oxidation test was carried out at 400 ℃, 410 ℃, and 420 ℃. Microstructural study confirms that both T4 and T6 alloys undergo grain coarsening with a grain size of 72.64 µm, and the orientation of the grains shifted from the pyramidal plane (2−1-10) to the basal plane (0001). The TEM investigation helps pinpoint the GP zone's genesis in T4 heat-treated AZ80. T4 AZ80 has a maximum ultimate tensile strength of 306 MPa and a ductility of 29.77% because of the dispersion-strengthening effect. The T6 AZ80, on the other hand, has a minimum corrosion rate of 0.158 mm/year in NaCl solution and an oxidation rate constant of 4.19 mg2.cm−4h−1 at 420 ⁰C. Notably, the T6 AZ80 shows significant peaks of Mg2Al3, and the as-cast shows more peaks of Mg17Al12. Magnesium alloy AZ80 is significantly affected by intermetallic phases like Mg17Al12 and Mg2Al3. The Mg2Al3 phase shows the latter tendency to resist corrosion and oxidation.

Pitting corrosion performance of plasma oxidized Cp-Ti and effects of fabrication methods

In this study, the electrochemical corrosion properties of commercial pure titanium (Cp-Ti) samples produced by additive manufacturing and forging were compared by plasma oxidizing. Plasma oxidizing processes were carried out at temperatures of 650 °C and 750 °C for 1 h and 4 h. Electrochemical corrosion experiments were carried out in Simulated Body Fluid (SBF) using open circuit potential, cyclic potentiodynamic polarization and electrochemical impedance spectroscopy methods. It was found that the coating thickness of F 750 °C-4 h and S 750 °C-4 h samples was the highest. The corrosion resistance of the samples produced by additive manufacturing is lower than that produced by forging due to the Lack of fusion (LOF) effect. The barrier layer developed by the plasma oxidizing process significantly improved the corrosion performance of additive manufacturing by reducing the LOF effect. The minimum corrosion rate was obtained at S 750°-4 h. While the total material loss due to corrosion was the lowest on this surface, the last corroded surface was F 750°-4 h. The maximum resistance was observed on the plasma oxidized surfaces for the group produced by forging.

Corrosion Studies of Temperature-Resistant Zinc Alloy Sacrificial Anodes and Casing Pipe at Different Temperatures.

In order to solve the problem of external corrosion of deep well casing in oil and gas fields, a new type of high-temperature-resistant zinc alloy sacrificial anode material was used. The temperature and corrosion resistance of the new anode material and TP140 casing were investigated by simulating the high-temperature working conditions of a deep well in an oil field using high-temperature and high-pressure corrosion tests and electrochemical tests. The results showed that at 100-120 °C, the corrosion rate of TP140 protected by a sacrificial anode was only one-tenth of that under unprotected conditions, and the minimum corrosion rate of TP140 protected by a sacrificial anode at 100 °C was 0.0089 mm/a. The results of the dynamic potential polarization curve showed that the corresponding corrosion current density of TP140 first increased and then decreased with the increase in temperature. The self-corrosion potential in sacrificial anode materials first increased and then decreased with the increase in temperature, and the potential difference with TP140 gradually decreased.

Preparing Ni–Mo coatings for high-temperature Na2S3 molten salt on aluminium

Pure aluminum was susceptible to corrosion as a casing material for sodium-sulfur batteries. In this context, the effects of different electrodeposition parameters on the sulfur anticorrosion of Ni–Mo alloy coatings on pure aluminum substrate were investigated through an orthogonal test. The corrosion process of aluminum with Ni–Mo composite coatings in Na2S3 molten salt at 350 °C was investigated by static immersion test. The results demonstrated that the optimum parameters for achieving high corrosion resistance coating were Na2MoO4·2H2O concentration of 10 g/dm3, current density of 5 A/dm2, pH value of 9 and temperature of 45 °C. The sodium molybdate content played a crucial role in determining the corrosion resistance of the coating. The grain size of the coating decreased and the Mo content increased accordingly as the sodium molybdate content increased. While the presence of Mo element exhibited inhibitory effects on corrosion, an increase in high-energy grain boundaries resulting from grain refinement had an adverse impact. Consequently, in the single-factor experiment with varying Na2MoO4·2H2O contents, when maintaining the sodium molybdate content of 10 g/dm3, the minimum corrosion rate was 0.02632 mm/y after corrosion in Na2S3 molten salt at 350 °C for 72 h. Additionally, it was found that NiS2 as a corrosion product could effectively inhibit further development of corrosion.

Effect of Yttria-stabilized zirconia coating on the corrosion and thermal behaviour of additive manufactured Inconel 718 alloy

The need for additively manufactured Inconel 718 alloy is increasing in high-temperature functional applications, including gas turbine engines, aviation engines, cast blades, and housings. The proposed work aims to improve the corrosion resistance and thermal characterization of additively manufactured Inconel 718 using a Yttria Stabilized Zirconia (YSZ) thermal barrier coating. YSZ is coated on the additively manufactured Inconel 718 alloy using a plasma spraying process. Using an electrochemical workstation, a corrosion test is conducted for the YSZ-coated Inconel 718 alloy and the non-coated Inconel 718 alloy. Thermal shock loading and thermal stability analysis for the YSZ-coated Inconel 718 alloy are carried out using a tubular furnace and a thermogravimetric analyser. YSZ-coated, additively manufactured Inconel 718 alloy is characterized by phases formed, microanalysis of corroded specimens, morphology, surface cracks, and elemental presence using X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Energy dispersive spectroscopy (EDS). YSZ-coated Inconel 718 alloy shows a minimum corrosion rate of 0.0000472 mm/year, which is better than the non-coated Inconel 718 alloy (5.93 mm/year). The YSZ coating on Inconel 718 alloy improved the thermal stability and thermal shock resistance better than the non-coated Inconel 718 alloy.

Experimental investigation on process parameters induced mechanical and microstructural properties for laser powder bed fusion additive manufacturing of SS316L

The effect of energy density on different mechanical, microstructural and surface properties was examined for laser powder bed fusion of additively manufactured stainless steel 316L (AM SS316L). The energy density was varied by changing laser power from 80 to 180 W to print AM SS316L samples. The investigations include various mechanical tests and microstructural characterizations such as tensile strength, hardness, density, roughness, wear and residual stresses. At an energy density of 84 J/mm3, maximum tensile strength, hardness and density were obtained as 640 MPa, 246 HV and 99.47%, respectively. However, a minimum wear rate of 1.9 (mm3/(N*m))*10−5 was achieved at an energy density of 84 J/mm3. Residual stresses were tensile on the top surface and varied with the energy density. The corrosion performance of SS316L was measured in Ringer's solution for bio-implant applications with the potentiodynamic polarization test. The minimum corrosion rate was obtained at an energy density of 37 J/mm3. The microstructure behavior with respect to different characterizations was examined. The non-homogenous grain growth was observed with the cellular and columnar grains. This study would help to find optimum parameters for desired mechanical and surface properties.

Effect of acidic solution and immersion duration on the corrosion behaviour of the aluminium 6061 alloy

The current investigation's goal is to examine the corrosion effect of aluminium 6061 alloys. The acidic immersion corrosion experiment was utilised to perform the corrosion test. The experiments were carried out in accordance with the L9 orthogonal array tables with two corrosion parameters: acidic solution and immersion duration with three levels. Taguchi’s methodology optimised the corrosion parameters to obtain a minimum corrosion rate on aluminium 6061 alloys. The results reveal that the chloride ions cause huge corrosion in the aluminium alloy samples dipped in a hydrochloric acidic solution. Meanwhile, significant possible corrosion happened in the initial stage of immersion of samples in the acidic solution. This is due to the termination of a protective aluminium oxide layer over the circumference area of the aluminium alloy. Moreover, the Taguchi technique revealed minor corrosion in the aluminium samples dipped in a nitric acidic solution (HNO3) for 216 h. Analysis of Variance (ANOVA) confirmed the contribution of two corrosion parameters on the corrosion rate of the aluminium alloy. The Scanning Electron Microscope (SEM) shows the presence of chloride traces over the surface of the highly corroded aluminium alloy.

Experimental and modeling analysis on the performance of 2-mercaptobenzimidazole corrosion inhibitor in hydrochloric acid solution during acidizing in the petroleum industry

In this work, the corrosion inhibition of carbon steel in 1 molar HCl solution was evaluated by experimental and modeling approaches using 2-mercaptobenzimidazole (2-MBI). To this end, an experimental design for the weight loss method using response surface methodology (RSM) was carried out and the corrosion rate (CR) and inhibition efficiency (IE) were determined. The study was completed at various values of temperature, exposure time, and inhibitor concentration to determine the optimal conditions for corrosion prevention. Using experimental data on the corrosion rate and inhibition efficiency of 2-MBI, new models were developed, the significance of which was tested using ANOVA-analysis of variance. The developed RSM-based CR and IE models were highly accurate and reliable, and their P-values were less than 0.0001. The novelty of this study lies in the newly developed model for the evaluation of 2-MBI inhibition performance and its application to high-temperature conditions in the petroleum industry. Besides, the R2-statistics (R2, adjusted-R2, and predicted-R2), adequate precision and diagnostic plots were used as main measures to verify the accuracy and adequacy of both CR and IE models. In addition, it was observed that inhibitor concentration had the most impact on both CR and IE models compared to other parameters due to its largest F-values (561.65 for CR and 535.56 for IE models). Moreover, the results indicated that adding 140–150 ppm of 2-MBI at low-level temperatures of 30–35 °C had the most interaction effect on the performance of the corrosion inhibition process. In this case, the CR was less than 0.9 mm/y and the IE more than 94%, even after a high exposure time of 105 h. Furthermore, numerical optimization of the corrosion inhibition process for 2-MBI showed that the optimum conditions for maximum IE and minimum CR were achieved at a concentration of 115 ppm, temperature of 30.7 °C, and exposure time of 60.4 h. Under these conditions, the efficiency and corrosion rate were 92.76% and 0.53 mm/y, respectively. Finally, the adsorption of 2-MBI on the sample surface was studied at various exposure times and temperatures. In all cases, the adsorption behavior obeyed the Langmuir isotherm. In this case, the Gibbs adsorption free energy varied from − 33 to − 37 kJ/mol, which reflects both physical and chemical adsorption of the corrosion inhibitor at all tested temperatures and test times.

Influence of welding parameters on mechanical and corrosion properties of Ti6Al4V alloy

Ti6Al4V is an alpha–beta grade 5 titanium alloy, which is the most commonly used of all the titanium alloys. Ti6Al4V alloy possesses a lot of desirable properties such as, weldability, heat treatability and resistivity against corrosion. Due to its outstanding strength-to-weight ratio and low modulus of elasticity it is widely used in jet engines, aircraft fuselage and defence armour. In this investigation, an effort has been made to determine the optimal welding parameters in welding of 3 mm thick Ti6Al4V alloy plate using Gas Tungsten Arc Welding – with filler (GTAWF), Gas Tungsten Arc Welding – Autogenous (GTAWA) and Laser Beam Welding – Autogenous (LBWA) techniques and weldability of Ti6Al4V alloy. The GTAWF, GTAWA and LBW techniques are fusion welding techniques having the welding input parameters as Voltage V (volts), Current I (ampere) and Feed F (mm/minute). The response from these welding processes are Tensile strength T (MPa), Joint efficiency η(joint)(percent), Impact strength I (Joules) and Corrosion rate CR (mils/yr). The optimal welding parameters were determined with condition that the welding parameters had high mechanical properties (tensile strength, joint efficiency, impact strength) and minimum corrosion rate. The optimal welding parameters yielded GTAWF weldments that exhibited relatively excellent mechanical properties and corrosion resistance compared to LBWA, whereas GTAWA weldments exhibited a mediocre performance.

Corrosion behavior and tribological-microstructural characterization of Al/ZrO2-Gr hybrid composite fabricated via Friction Stir Processing

The present study investigates the microstructural evolution, tribological properties, and corrosion behavior of hybrid metal matrix composites reinforced by a combination of graphite (Gr) and zirconia (ZrO2) particles fabricated by Friction Stir Processing (FSP). To do so, microstructural characterization was carried out by optical microscopy (OM) and electron backscatter diffraction (EBSD) analysis. In addition, pin-on-disk, microhardness measurement, potentiodynamic polarization, and electrochemical impedance tests were conducted to evaluate the tribological and corrosion behavior of the samples. Results showed that employing four passes of FSP led to significant grain refinement in stir zones because of dynamic recrystallization (DRX), particle-stimulated nucleation (PSN), and Zener pinning effect. Furthermore, the EBSD results illustrated that the average grain size area has significantly decreased from ∼115 µm2 in the only FSP-treated specimen to ∼1.2 µm2 in the hybrid composite. Also, the presence of the secondary phase particles caused an increase in the fraction of the high-angle grain boundaries (HAGBs) compared to the only FSP-treated specimen. The results of the pin-on-disk test revealed that the wear resistance improved in the particle-reinforced composites and, on the other hand, decreased in the FSP-treated sample compared to the base metal (BM). Furthermore, the lubricant effect of the Gr particles contributed to a pronounced reduction in the coefficient of friction (COF) and weight loss in the Gr-containing composites such that the COF of the hybrid composite and Gr-reinforced mono-composite dramatically decreased by ∼0.52 and ∼0.37, respectively. The corrosion behavior of the FSP-treated sample demonstrated better resistance compared to the BM. In addition, the particle-reinforced composites exhibited better corrosion resistance than the FSP-treated sample and BM, especially the Al/Gr mono-composite which had the minimum corrosion rate and the most positive pitting potential (Epit), making it the most pitting-resistant sample in comparison to other specimens.

Enhanced anticorrosion properties of composite coatings containing polyvinyl butyral and polyaniline-carbonized polyaniline

A kind of polyaniline-derived carbon material, polyaniline‑carbonized polyaniline composite (PANI-CPANI), was realistically applied to the polyvinyl butyral (PVB) resin matrix. The corrosion resistance of PVB/PANI-CPANI composite coating on 304 stainless steel has been investigated. The composites were characterized by Fourier transform infrared spectroscopy and X-ray diffraction. The surface morphology of the coating exhibited that the composite was uniformly dispersed. The tribological test proved the excellent mechanical properties of the coating. The adhesion of the coating reached grade 5B. Based on electrochemical test results, PVB/PANI-CPANI coating possessed the maximum low-frequency impedance and minimum corrosion rate under different corrosive environments. The long-term corrosion protection to the substrate could last for over 240 days in 3.5 wt% NaCl solution. This work could be a new application of polyaniline derivatives in the anticorrosive coating field.

Microstructure, mechanical and corrosion behaviours in friction stir welding of dissimilar magnesium alloys

AbstractUsing magnesium alloys reduce the weight of a vehicle considerably, but the available fusion welding methods impose restrictions on the fabrication of magnesium alloy components. Friction stir welding is an efficient method to weld magnesium alloys, but due to extreme plasticization and stirring of materials, the microstructures are transformed. Similar to other alloys, friction stir welded magnesium alloys are also susceptible to corrosion. In the present work, dissimilar AZ31 and AZ91 Mg alloys were friction stir welded at varying welding conditions. The variable presence of small cracks with a high amount of oxide, and microstructural and textural differences result in varying joint strength, that is, joint efficiency, which has a maximum value of approximately 90% of a stronger base material. The maximum corrosion potential obtained in welded zones is approximately equal to a base material that conveys similar electrochemical behaviour. The minimum corrosion rate of 0.22 mm/year is observed in the sample welded at 700 rpm tool rotational speed, 30 mm/min welding speed and 18 mm shoulder diameter.

Corrosion behavior of copper, aluminium, and stainless steel 316L in chicken fat oil based biodiesel-diesel blends

This study investigates the corrosion behavior of automotive materials in bio-based fuels. The Response Surface Methodology is employed to evaluate the corrosion rates of materials such as copper, aluminium, and stainless steel when they are exposed to chicken fat-based biodiesel. Copper, aluminium, and stainless steel showed minimum corrosion rate at a blend percentage of 5.86 % when they were immersed for 920 h and maximum corrosion rate at blend percentage 34.14 % when these were immersed for 920 h. Meanwhile, the maximum corrosion rate was observed at a blend percentage of 34.14 % corresponding to the same immersion period. Optimum values indicated by RSM for copper and aluminium were noted at a blend percentage of 10 % and an immersion period of 720 h. Similarly, for stainless steel 316 l, these were 10.91 % and 754.44 h, respectively. Additionally, trials using the B100 for 920 h were conducted on copper, aluminium, and stainless steel 316 l, and the results showed considerably higher corrosion rates than those previously found. The surface morphology of the materials was investigated by X-ray Diffraction and Scanning Electron Microscopy, and it was revealed that copper was the most corrosive material in chicken fat oil-based biodiesel followed by aluminium and stainless steel 316 l.

Effects of Heat Treatment and Diamond Burnishing on Fatigue Behaviour and Corrosion Resistance of AISI 304 Austenitic Stainless Steel

The surface cold working (SCW) of austenitic stainless steel (SS) causes martensitic transformation in the surface layers, and the percentage fraction of the strain-induced martensite depends on the degree of SCW. Higher content of α′−martensite increases the surface micro-hardness and fatigue strength, but deterioration of the corrosion resistance is possible. Therefore, the desired operational behaviour of austenitic SS can be ensured by the corresponding degree of SCW and heat treatment. This article evaluates the effects of SCW performed by diamond burnishing (DB) and heat treatment on the surface integrity (SI), rotating fatigue strength, and corrosion resistance of AISI 304 austenitic SS for two initial states: as-received hot-rolled bar and initially heat-treated at 1100 °C for one hour followed by quenching in water. Then, DB was implemented as a smoothing and hardening process, both alone and in combination with heat treatment at 350 °C for three hours after DB. The electrochemical performance was examined by open circuit potential measurements, followed by potentiodynamic tests. For both initial states, smoothing DB provided the lowest roughness, whereas an improvement in the maximum surface micro-hardness was obtained after hardening DB and subsequent heat treatment. The maximum fatigue strength was obtained by hardening multi-pass DB without subsequent heat treatment for the as-received initial state. Smoothing DB and subsequent heat treatment maximised the surface corrosion resistance for the two initial states, whereas a minimum corrosion rate was obtained for the initially heat-treated state. For the as-received state, smoothing DB and subsequent heat treatment simultaneously lead to a high fatigue limit (equal to that obtained by hardening single-pass DB) and a low corrosion rate.

Investigation of Magnesium and Chromium Fillers FSW Dissimilar Joint of AA6063 and AA 5154

Friction stir welding (FSW) is a solid-state metal joining process. There is no melting and recasting of metal while welding is used. Some of the defects commonly encountered in FSW are tunnel defect, bond, cracks, pin holes, and pipping defects. The defects occur because of improper metal mixing and less heat input in the weld nugget zone. In the fusion welding process, a filler rod is employed to form a quality weld with superior mechanical properties. In this work magnesium and chromium powders are used as filler materials. The purpose of this study is to ascertain whether filler materials and manufacturing processes have an impact on the weld nugget zone spot weld joint formation as well as the mechanical and abrasive properties of welded joints. This study's FSW filler materials mixing ratio and process parameters were improved by using the Central Composite Design (CCD) idea, which is discussed in more detail below Response Surface Methodology (RSM). The best empirical relationship between the parameters was provided by the CCD. The mathematical relationships were established to forecast the maximum tensile strength, maximum weld nugget hardness, and minimum corrosion rate by incorporating filler materials with process parameters. The optimal processing factors combination is predicted by conducting the validation test. The optimum parameters were the tool rotatory speed 600–1000 revolution per minute, welding speed 60 to 180 mm/min, plunge depth of 0.05 to 0.25 mm, center distance between the sample is 0–4 mm, as well as powder mixing ratio of 90 : 10, 92.5 : 7.5, 95 : 5, 97.5 : 2.5, and 100 : 0, the tensile test, microhardness, and corrosion rate analysis were conducted on the weld specimen. The welded test specimen provides better joint strength, weld nugget hardness, and enhanced corrosion resistance properties. The microstructure analysis shows the fine grain structure and homogeneous distribution of filler material with the base metal in the welded area.

Study of microstructure and corrosion resistance of FeCrAl-Gd alloys

The corrosion resistance of Fe–21Cr–4Al alloys with different gadolinium (Gd) contents was investigated by means of microstructure, salt spray corrosion and electrochemical tests. The microstructural analysis shows that Gd and Gd2O3 formed at grain boundaries will pinch the grain boundaries and slow down the grain growth, thus reducing the grain size. The corrosion results showed that as with the increase of the Gd component, there are two competing corrosion mechanisms: 1) the grain size becomes smaller, which makes the corrosion pit difficult to expand; more Gd oxides are formed, which hinders the penetration of Cl−; 2) the number of grain boundaries and dislocations increases, which expedite the corrosion rate; and the increasing Gd-rich phase serve as cathodes for the micro-galvanic corrosion. A minimum corrosion rate of 1.94 mm/year was achieved for the Gd-containing alloy, a reduction of 46.4% compared to the original alloy.