Effect of vanadium and rare earth (RE) oxide hardfacing on mechanical and sliding wear behavior of Fe based alloy

Hardfacing is one of the preferred ways to prolong the life of machine components. In the current paper, efforts have been made to evaluate the flux composition on the hardness and wear behavior of a hard-faced surface. The shielded metal arc welding process was used to deposit the hardfacing layer over low carbon steel. Six different types of iron-based multicomponent flux compositions were developed using FeCr (25–30%), FeV (5%), FeMo (3–4 %), FeTi (2–3 %), Nb (3–4 %), and CeO2 (1–5 %) for hardfacing. The properties of the overlayer were examined using the microstructure study, hardness study, and abrasive wear test. Microstructural characterization was done using an optical microscope and field emission scanning electron microscope. X-ray diffraction was performed to examine the nature of precipitate formation. The worn-out surface and the debris were further examined, employing scanning electron microscopy to study the wear mechanism. The hard-faced surfaces revealed the presence of columnar and dendritic grains. Equiaxed grains were also observed in the sample, which was hard-faced with FeV. The hardness of the hard-faced surfaces was determined using the Vicker’s macro-hardness tester. A maximum hardness of 846.5 ± 2.5 HV was observed for weld overlay. The sliding wear behavior of the surface was investigated using an abrasive wear test performed on the pin-on-disk apparatus. The addition of vanadium to Fe-Cr-C hardfacing flux increased hardness and wear resistance between 3.5 and 6 times, respectively.

Robust Parameter Design of Shielded Metal Arc Welding (SMAW) for Optimum Tensile Strength

Shielded Metal Arc Welding (SMAW), an arc welding process, is widely used in applications. In practice, SMAW is widely applied to the welding process on hollow square pipe. Performance expected from this welding is the tensile strength of weld joint. The tensile strength is influenced by parameters process which have possibility for an optimization process to become ‘robust’. Robust is a design which less sensitive to the effect of uncertain quantities or noise factors. Taguchi method is the most efficient optimization method which accommodates the noise factors effect and requires less experiment. This study is focusing on optimizing the welding process on hollow square pipe. Parameters process such as welding current (I), electrode angle (θ), root gap (d) and electrode type (E) are adopted as parameters design. Taguchi method are chosen as a strategy and L9 fractional orthogonal array are chosen as the design experiment, which only 9 experiment samples needed from 81 experiments that should have been carried out for full factorial design. The objectivity is to maximize the tensile strength of weld joint. Three replications of L9 fractional orthogonal array Taguchi had been performed to generate the tensile strength and estimates the fluctuation of the output caused by noise factors. This study found that the welding current of 100A (I), electrode angle (θ) of 90°, root gap (d) of 2 mm, and electrode type (E) of E7018 produce the optimum results. Tensile strength improved from this robust parameter design is about 98.39 MPa based on initial parameter design.

Influence of different hard-facing procedures on quality of surfaces of regenerated gears

During the process of regeneration of machine parts, certain phenomena occur that have a significant impact on the loss of their working ability. Hereditary properties are expressed by the interdependence of geometric and physical-mechanical-metallurgical parameters of gear teeth created during the technological operations of regeneration of worn teeth by hard-facing. The influence of the type of additional material (electrodes and their combinations) on the tribological characteristics of welded gear teeth was considered, whereby the so-called hard additional materials were applied. Those are the additional materials that give the required surface hardness of the teeth without subsequent thermal or thermochemical treatment. This research did not involve the regeneration of specific worn gears removed from machine systems, but the new gears were made, which were then damaged and then regenerated by hard-facing using the shielded metal arc welding (SMAW) procedure. Thus, all the tested gears were made of the same material, belonged to one batch and were machined on the same machines with the same machining regimes. The tests were performed on samples made of 20MnCr5 steel for cementation, on a tribometer by the “block on disc” method, which was designed to simulate the operating conditions of coupled teeth of concrete gears in the exploitation conditions. Based on the conducted tribological tests, the average coefficients of friction and topography of the surfaces were determined by measuring the wear trace and it was defined which additional materials give the best tribological characteristics of the surfaces of gears regenerated by hard-facing.

Current trends in welding flux development

Welding flux makes significant contribution to weld-metal quality, productivity of welding process and rapid deployment of new materials. Deployment of new materials has been hampered because of lengthy trial-and-test experiments and paucity of methodology for modelling and optimisation in the traditional welding flux development. This paper discussed the contributions made to mitigate the drawbacks of traditional welding flux development in areas of experimentations, prediction modelling and optimisation. Limitations of current efforts were identified and suggested for future research, namely (i) current response models are limited to well-behaved flux systems and do not account for edge and additive effects of flux ingredients (ii) non-incorporation of stakeholder’s preferences concerning the relative importance of quality attributes (iii) lack of prediction and optimisation tools for determining optimal coating factor and flux heights for Shielded Metal Arc Welding and Submerge Arc Welding respectively and (iv) non-continuous response functions and concave regions of the trade-off surface are not considered.

WELDING ANALYSIS OF GRAY CAST IRON ASTM A48 CLASS 40 USING SMAW

The mechanical and physical characteristics of gray cast iron are intricately bound to its application as an essential material in manufacturing various goods. SMAW (Shielded Metal Arc Welding) is the most simple and widely used electric arc welding method. In this work, ASTM A48 gray cast iron Class 40 was joining using the SMAW method with the welding position used was 1G or underhand position. The joining used is the Butt Joint using an open Singel V seam with a current of 120A. The joining of Welding was characterized through dye penetrant and hardness tests. Rockwell hardness tests on base metal and heat affected zone reveal that the heat affected zone has the highest hardness value of 56.5 HRC, while the base metal has the lowest hardness value (41 HRC). Graphite, pearlite, and pearlite were all visible in the microstructure study.

Pengaruh Variasi Arus pada Pengelasan Baja ST37 Menggunakan Las Shield Metal Arc Welding (SMAW) dengan Posisi Pengelasan 3F

Welding is a very important part in the development and growth of the industry because it has a role in engineering, repair and construction. Shielded metal arc welding (SMAW) is the process of joining two or more materials using a wrapped electrode as heat energy to melt the material. The purpose of this study was to determine the effect and welding defects that arise with current variations so that the optimal welding results obtained from 3 amperes were tested using E6013 electrode diameter 3,2 at the 3F welding position fillet joint. This study uses an experimental method with the material used is St 37 steel with a current variation of 90A, 100A, and 110A. From the research conducted, it was not found optimal welding results where from each ampere tested there was still a weld defect. The defects that occur in the three amperes are caused by the arc, electrode angle, and arc length that exceed the normal limit and are also influenced by the welding speed. From the three variations of the amperage used, the dominant welding results did not occur, namely the 90 amperage, while the 100 amperage welding leg showed good results.

Corrosion Behavior of CW6MC Nickel Cast Alloy (Inconel 625) Welded by Shielded Metal Arc Welding

The aim of this study concerns the effect of multi-pass shielded metal arc welding (SMAW) on the corrosion behavior of CW6MC cast nickel alloy. Using optical and SEM techniques the welded joint is analyzed. Vickers microhardness mapping and potentiodynamic polarization in NaCl and H2SO4 solutions are also evaluated. Both the Laves phase and NbC-type carbides are identified in the base metal (BM) and weld metal (WM) regions. The main microstructural difference observed between these regions is the morphology aspect and fineness of the dendritic arrays. The welding process promotes the finer columnar grains formation with refined intermetallic particles in the WM than equiaxed grains of the BM, which in turn results in higher microhardness values in the former region. However, no substantial changes were observed in the corrosion behavior between the BM and WM regions, considering both acid and saline media. Nevertheless, during the multi-pass SMAW process, some non-metallic micrometric inclusions (Mo and S-rich regions) can be constituted to occur in the WM region. This is associated with a significant drop in the corrosion performance of this region when the electrochemical tests are evaluated.