Effect of Alumina Addition on the Microstructure and Mechanical Properties of Metal Inert Gas Welded Low Carbon Steel

Friction Stir Welding of AA6082 Thin Aluminium Alloy Reinforced with Al2O3 Nanoparticles

Abstract: In this present investigation, AA6082-T6 thin aluminium alloy plates of 2 mm thickness were friction stir welded using fine ceramic Al2O3 nanoparticles as the reinforcing materials between the adjo...

Experimental Investigation of TIG-welded AISI 1008 Carbon Steel

Abstract: Carbon steel is widely used in engineering applications due to its exceptional mechanical properties, and low cost. The fabrication technique employed to weld carbon steel plays a vital role in the final performance of the welded component when put into service. TIG welding is a generally accepted arc welding technique due to its ease and versatility coupled with its capacity to produce high-quality welds. It is the most desirable technique employed for welding plain carbon steel. This work aims to evaluate the influence of TIG welding process parameters on the mechanical and microstructural properties such as tensile strength, hardness, and microstructure of AISI 1008 carbon steel. The process parameters considered in this work were the TIG welding current, and gas flow rate. The tensile testing and the Vickers hardness testing have been carried out for the welded samples. The microstructural investigation was also carried out for the fusion zones (FZ) and the heat-affected zones (HAZ). The test results were analyzed, and emerging properties were compared for the various set of parameters. Welded specimen produced with 140 A, 15 L/mm had the highest hardness value. However, the highest average ultimate tensile strength of 432.89 MPA was produced from process parameters 180 A, 19 L/mm. Finer grain structures were seen in the fusion zones as compared to the heat-affected zones for all selected parameters.

Hybrid fiber laser – Arc welding of thick section high strength low alloy steel

Abstract: Hybrid laser – metal active gas (MAG) arc welding is an emerging joining technology that is very promising for shipbuilding applications. This technique combines the synergistic qualities of the laser and MAG arc welding techniques, which permits a high energy density process with fit-up gap tolerance. As the heat input of hybrid laser – arc welding (HLAW) is greater than in laser welding, but much smaller than in MAG arc welding, a relatively narrow weld and restricted heat affected zone (HAZ) is obtained, which can minimize the residual stress and distortion. Furthermore, adding MAG arc can increase the penetration depth for a given laser power, which can translate to faster welding speeds or fewer number of passes necessary for one-sided welding of thick plates. In this work, a new hybrid fiber laser – arc welding system was successfully applied to fully penetrate 9.3 mm thick butt joints using a single-pass process through optimization of the groove shape, size and processing parameters.

Effect of nickel and molybdenum additions on weld metal toughness in a submerged arc welded HSLA line-pipe steel

Abstract: The effects of alloy additions of nickel (Ni), molybdenum (Mo), and Ni and Mo together on the impact toughness of an API HSLA-70 steel by submerged arc welding in the laboratory were investigated and micro-structural factors which affect the impact toughness were discussed. Ni additions resulted in a low impact toughness and an increased fracture appearance transition temperature (FATT) in weld metal (WM). The above influences of Ni should be attributed to the formation of acicular ferrite (AF) suppressed by increasing the Ni content. Conversely, the combined presence of Ni and Mo in the WM decreased the volume fractions of grain-boundary ferrite (GBF) and promoted formation of high toughness of AF. The increase of Mo content created an acicular ferrite-predominant weld metal microstructure with impressively improved toughness. Mo addition of 0.881 wt.% in the WM gave the optimal impact toughness at −45 °C with a microstructure of 77% AF and 20% granular bainite (GB).

Optimization of deep penetration laser welding of thick stainless steel with a 10kW fiber laser

Abstract: Deep penetration laser welding of 12 mm thick stainless steel plates was conducted using a 10 kW high-power fiber laser. The effect of the processing parameters on the weld bead geometry was examined, and the microstructure and mechanical properties of the optimal joint were investigated. The results show that the focal position is a key parameter in high-power fiber laser welding of thick plates. There is a critical range of welding speed for achieving good full penetration joint. The type of top shielding gas influences the weld depth. The application of a bottom shielding gas improves the stability of the entire welding process and yields good weld appearances at both the top and bottom surfaces. The maximum tensile stress of the joint is 809 MPa. The joint fails at the base metal far from the weld seam with a typical cup–cone-shaped fracture surface. The excellent welding appearance and mechanical properties indicate that high-power fiber laser welding of a 304 stainless steel thick plate is feasible.

Microstructure, adhesion, microhardness, abrasive wear resistance and electrical resistivity of the plasma sprayed alumina and alumina–titania coatings

Abstract: Al 2 O 3 and its mixtures with TiO 2 powders were prepared by a fused and crushed method. Prepared powders were sprayed at 10, 12 and 16 kW power in atmospheric plasma spraying. Microstructure of the coatings was analysed by SEM. Alumina coatings showed better quality than composite coatings. Different types of pores were observed in alumina–titania (AT4016) coating. Pore forming mechanisms are reported. Adhesion strength, microhardness and abrasive wear resistance of alumina and alumina–titania coatings were measured and results are explained. The influence of the power to the plasma torch, powder particle size and its distribution and feed rate of the powder on the abovesaid properties of the coatings are explained. Electrical resistivity was measured in composite coatings. The electrical conductivity increases with increased titania content in the coating.