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Welding joint Austenitic stainless steels can undergo intergranular corrosion attack in some service conditions, such as oil refineries, petrochemical plants, and industrial furnaces operating at high temperatures (between 500°C and 675°C). This research focuses on fabricating dissimilar metal welds to avoid failure due to sensitization and investigate stress-relieved carbon steel by Post-weld heat treatment (PWHT). This work studies a dissimilar weld joint (DWJ) of ASTM 335 grade P11 joint to ASTM 304L and PWHT after welding. These welding processes are used in multi-pass gas tungsten arc welding (GTAW) using filler metal R309L. PWHT at temperatures of 550 °C with holding times of 40, 50, and 60 minutes and then slow cooling in atmospheric air temperature, It was used to compare the results holding time carbon steel ASTM A335 Gr. P11 while processing. Holding time at 50 minutes has the maximum result of PWHT with 182 HV and has a good distribution of perlite with fine grain and increasing holding time also increases formed carbide on the grain boundary of stainless steel 304L.

The study was conducted to evaluate the impact toughness of flux-cored arc welded of SM570-TMC steel joint under different heat inputs, 0.9 kJ/mm (low heat input) and 1.6 kJ/mm (high heat input). Welding wire containing 0.4%Ni was selected on this experiment. Multi-pass welds were performed on SM570-TMC steel plate of 16 mm in thickness with a single V-groove butt joint on flat position (1G). The evaluation consists of observations on microstructure using an optical microscope and SEM-EDS, and mechanical properties including tensile, microhardness Vickers and Charpy V-notch (CVN) impact test at temperatures of 25, 0 and-20 °C. Results showed that the impact toughness of the base metal (BM) was higher than the weld metal (WM) at all test temperatures. Hardness and impact toughness of WM at low heat input was observed higher than when applied a high heat input. The welded samples at low and high heat inputs had high of tensile strength, and the fracture seemly occurs on the BM. Microstructure observation showed that at a high heat input, larger grains and microsegregation were observed. It might affect on decreasing their impact property.

Dissimilar metal welding was mostly done to optimize the application and engineering requirements with economic considerations. Weld microstructures greatly influenced the mechanical properties of welded joints. The investigations were carried out to evaluate the microstructural and mechanical properties of dissimilar weldment between carbon steel ASTM A36 and austenitic stainless steel 304 with a variation of welding position (1G, 2G, 3G) and weld thickness (6 mm to 12 mm) joints by TIG welding. A detailed analysis was conducted on the weld zone composition, the microstructural, and mechanical properties. The results show that the welding position and thickness of the weld joints influenced the microstructure both in HAZ and weld metal. Size, distribution, and orientation of microstructure were improved and more uniform with increasing of welded joint thickness. In HAZ carbon steel, GB ferrite was dominant, especially for the flat welding position (1G), while for the horizontal position (2G) and the vertical welding position (3G) showed other structures such as Widmanstaten ferrite, hard-structures like martensite and bainite. In the region near the fusion line and the weld metal, the chemical composition changed due to thermal convection, diffusion, and macro-segregation caused by penetration of liquid metal carbon steel into the weld pool. SEM/EDS results indicated diffusion of carbon from carbon steel A36 to stainless steel 304 and formed the hard-structure along the fusion line. The mechanical test results showed that the tensile test breaking point occurred in the parent metal of carbon steel A36. The bending test results showed very high stress on the face side of the welding joint, and there are no cracks from the bending test result. Vickers hardness testing showed that the hardness distribution increased from the carbon steel HAZ to the stainless steel HAZ, and the maximum hardness has achieved the value of 297 Hv at the fusion line of stainless steel 304.

Tungsten Carbide (WC) hard coating is widely used to coat the surface of the steel tools which provide tribological properties. In this paper, 0.25 wt% & 0.35 wt% of Carbon Nanotubes (CNT) were mixed with tungsten carbide (WC) powders as the feedstock powders. Method of solution dispersion in ethanol media using an ultrasonic device was used for coating the surface of WC powders with CNT powder. The mixed powders were then used as the feedstock powder to coat onto the surface of tool steel using the flame spraying process. The coated surface microstructures were observed under a scanning electron microscope (SEM), x-ray diffraction (XRD), and the energy dispersive spectroscopy (EDS) was used for the phase characterization and identification. The wear rate of coated steels was determined using the Ogoshi machine, and the Vickers hardness method used to measure their microhardness. The effects of CNT on the microstructure of the coated material and the surface mechanical properties were investigated. The results showed that the mixture powder preparation using an ultrasonic method in SDS solution and the ball-milling process was suitable to disperse the CNT on the surface of WC feed powders due to produce an adequate relationship between CNT' and WC powders increasing the surface mechanical properties of coatings. The wear resistance of the coated material produce using the mixture of WC powder with 0.35 wt% CNT increased around 50% higher than the WC coated steel without CNT addition. Also, the hardness of coating reinforced CNT increased significantly compared with the hardness of WC coated and the steel substrates. Microhardness value from the base metal to the WC-CNT coated steel increased from 550 HV to 1717 HV and also the wear rate from the base metal to the WC-CNT coated steel decreased from 0.86 mm3/min to 0.017 mm3/min. These results indicate that CNT is an excellent alternative to improve the surface mechanical properties of WC coatings.

This work investigated microstructure and impact toughness of multi-pass flux-cored arc welded SM570-TMC steel. A comparison was made between weldments fabricated with average heat input of 0.9 kJ/mm and 1.4 kJ/mm, respectively. SM570 steel plate with 16 mm nominal thickness and 1.2 mm diameter of E81-Ni1 flux-cored wire were selected in this experiment. Multi-pass flux-cored arc welding (FCAW) was performed using carbon dioxide shielding gas. Then the weldments were observed using optical microscopy, scanning electron microscope (SEM) and electron probe micro analyzer (EPMA). The steel joint strength was measured via tensile test, and Charpy impact test was performed at three different test temperatures. The microstructure observation exhibited the base metal mainly consist of ferrite and pearlite features, while the weld metal contained the acicular ferrites, polygonal ferrites and M-A constituent at both different heat inputs. The impact toughness of base metal is superior than weld metals. The weld metals fabricated at average heat input of 0.9 kJ/mm have a higher low temperature impact toughness than using heat input of 1.4 kJ/mm. The acicular ferrites amount that significant reduced at the higher heat input may degrade the toughness at low temperature.

Thermal spray is often applied on steam turbine blade leading edge to increase abrasion resistance. Stellite 1 is one of the commonly used material as it is known to wear protection against abrasion, oxidation, and corrosion at elevated temperature. This paper evaluated microstructure, hardness, and surface cracks of HVOF-sprayed Stellite-1 coating applied to the steam turbine blade. Optical microscopy reveals that all cracked and no-cracked coating have similarity in the microstructure. Typical 1.89% porosity was found on the specimen. The unbonded interface between the coating and substrate was also located to about 38% in length. All samples have 4.1% different in coating hardness with an average value of 718 HV. Coating thickness has a relation with the amount of porosity produced. Analysis of variance showed that both of the thickness and the hardness of coating are influencing the coating in making the penetrant indication. The microstructure showed a less dense coating with apparent porosity and unbonded interface when compared with other HVOF experiment. Blasting with excessive pressure and or the improper angle have made an alumina deposit at and below interface which may interfere with coating adhesion. Chromium Carbide and Silicon Oxide are formed near the porosity of coating.

HY-80 is the high yield steel that commonly used for naval ship and submarine. Arc welding operations are critical stage in fabrication of this steel. During welding, the problem may occur in the heat affected zone due to the high temperature makes the microstructure suddenly changes. Coarse grain heat affected zone (CGHAZ) develops close to the fusion line, steel become brittle and the impact toughness decrease. This research investigated the microstructure of HY-80 weldment, impact toughness at sub-zero temperatures, and hardness distribution along cross-section of the welded joint. ER100S welding wire, Ar+10%CO2 shielding gas mixture and single V-groove butt joint with an angle of 60° were selected prior to welding. 12 mm thick of HY-80 steel plate that used in this experiment was multipass welded by gas metal arc welding (GMAW). Impact toughness at sub-zero temperature, hardness and microstructure evolutions of base metal (BM), heat affected zone (HAZ) and weld metal (WM) were observed. The result shows at a temperature of-80 °C, the lowest impact toughness was measured at WM (61 J) as compared to fusion line (101 J) and BM (217 J). The hardness measurement shows the maximum hardness was measured in CGHAZ followed WM and BM. Vickers hardness test result of weld joint at bottom area are higher than top area. It may caused of the low heat input of back weld compared to other passes. The lower heat input, cooling rate increased and initiate the formation of hard phase. The microstructure of WM shows acicular ferrites and non-metallic inclusions, these inclusions may deteriorate the impact toughness.

Aluminum and stainless steel are metals that have some mechanical property advantages. Welding technology has been developed to join both different and dissimilar metals applied in a construction. The property advantages have been used to improve the performance of a construction. However, welding performance still creates a problem as a result of properties’ differences in metals. This study investigated the mechanical properties of a steel-aluminum joint with the thickness of less than 1 mm, welded by resistance spot welding (RSW); it is called a micro-RSW. Mechanical properties of the joint were analyzed by tensile test and were measured at the fracture area on the tensile test specimen. Moreover, it also analyzed intermetallic microstructure in the nugget or welding joint. Welding time of 8 CT was an optimum parameter on a welding process to get the maximum load. The fractographic structure of a stainless steel-aluminum joint showed a brittle nugget. Moreover, the fracture area on the aluminum side was larger than that of the stainless steel. Intermetallic compound (IMC) was created by melting and joining it through the heat input in the welding process. IMC in SS301-AA1100 nugget affected a brittle joint.

Technology of Friction Stir Welding (FSW) as a technique for joining metal is relatively new. In some cases on Aluminum joining, FSW gives better results compared with the Arc Welding processes, including the quality of welds and less distortion. FSW can even use milling machine or drilling machine, by replacing the tools and the appropriate accessories. The purpose of this study is to analyze the effect of process parameters on micro Friction Stir Lap Welding to the tensile load of welds. In this case, Aluminum material A1100, with thickness of 0.4 mm was used. Tool material of HSS material was shaped with micro grinding process. Tool shoulder diameter was 3 mm, while the diameter pin was 2 mm and a length of pin was 0.7 mm. The parameter variations used in this study were the variable of spindle speed (2300, 2600, and 2900 rpm), variable of tool tilt angle (0, 1, 2 degree) and a variable of Feed rate (50, 60, 70 mm/min). Where the variation of these parameters will affect to the mechanical properties of welds (as response) was the tensile load. Analysis and optimization parameters between the micro FSLW parameters with the tensile load of welds, is used a Response Surface Methods (RSM). From the result of experiment and analysis, it is shown that the important welding parameter in Micro Friction Stir Lap welding process is tilt angle.

Joining of dissimilar metals is to compose different properties of metals in order to minimize material costs and at the same time to maximize the performance of the equipment and machinery. There are a lot of methods of joining of dissimilar metals. However, the fusion welding is mostly used in a wide range of industries. This research is carried out for the process of dissimilar welding between carbon steel plates of ASTM A516-70 and austenitic stainless steel plates ASTM A214-316L by using gas metal arc welding (GMAW). Welding design used is a V-groove by using the buttering process and without buttering (non-buttering) process. Types of filler metals used are ER309L and ER316L-Si. The weldment is then tested by using destructive test (DT) and non-destructive test (NDT). Weldment is also characterized by using X-Ray Diffraction (XRD). The results show that the mechanical properties of weldment with buttering process are better compared with the weldment with a non-buttering process. The macro and microstructure of weldment with buttering process revealed finer grained and homogeneous structures compared with the one by using a non-buttering process. Moreover, welds characterization by using XRD show that the precipitation of chromium carbide on HAZ of weldment with buttering process is lower than that of weldment with a non-buttering process.

The emergence of white layer in each process of Electric Discharge Machining (EDM) becomes the focus of attention of the experts. It is harder than the base metal would be advantageous to withstand friction engine components, such as the plastic molding industry. From various studies it has been reported that the increase in the value of hardness of white layer either due to migration of the electrode material and dielectric fluid to the white layer. This paper discusses the influence of electrodes Cu, CuCr and graphite as well as jatrophacurcas dielectric fluid to the surface of the material SKD 61, microhardness of the white layer, Tool Wear Rate (TWR) of Material Removal Rate (MRR), Surface roughness (Ra) and the microstructure. Initial studies conducted are the transesterification and characterization of jatrophacurcas to determine the dielectric strength and the content of metal elements. Furthermore, the EDM testing is done to dies steel of SKD 61 using the electrodes of Cu, CuCr and Graphite. The use of jatrophacurcas yield the best MRR when using Graphite electrodes followed Cu last CuCr. While the smallest TWR produced by Cu electrode, CuCr and then the highest is Graphite. The relative wear which is the ratio TWR with MRR, for the three types of electrodes is always great at a small current then decreases and then tends to be stable with the increase of electric current. Jatrophacurcas for the three types of electrodes provide higher TWR than kerosene. This means that migration of materials is beneficial because larger material, but in terms of the geometric accuracy of the product can lead to decreasing of dimensional tolerances. Vickers hardness values of white layer is achieved by CuCr electrodes, Graphite lowest. Microstructural observation results of EDM white layer using graphite electrodes produce a more uniform thickness than the white layer using Cu and CuCr electrodes. The conclusion of this study that jatrophacurcas can be used as a dielectric fluid in EDM process, because electrode wear during EDM process is relatively high compared with kerosene that is mean more profitable in the surface treatment process of dies steel of SKD 61.

Indonesian government policy to convert energy consumption for domestic household from kerosene to liquefied petroleum gas (LPG) may lead to the increasing demand for LPG storage tank. LPG storage tank with a large capacity generally used the HSLA steel material of ASTM A516 Grade 70 joined by SMAW or combination between SMAW and SAW method. The heat input can affect the microstructure and mechanical properties of the weld area. The input heat is proportional to the welding current and the arc voltage, but inversely proportional to its welding speed. The result shows that the combination of SMAW-SAW process yield the lower hardness in the HAZ and the fusion zone compared to the singe SMAW process. PWHT mainly applied to reduce residual stress of welded joint. The result shows that PWHT can reduce the hardness in the HAZ and the fusion zone in comparing with the singe SMAW process. The microstructure of weld joint shows a coarser structure in the combined welding process (SMAW-SAW) comparing with the single welding process (SMAW).