Weld Overlays Research Articles

Investigations on hardfacing and wear characteristics of nickel-based Inconel 625 overlaid welds over AISI 347 pipe

The article focuses on investigating the effect of process parameters and wear behaviour of overlaid welds. Gas metal arc (GMAW) hardfacing is widely employed for repairing and to improve the performance of the engineering components. In this research, hardfacing is performed in the range of 130–150 A with filler wire of Inconel alloy (IN625) on the AISI 347 substrate. Successful overlaid welds were made for 150 A current at a speed of 250 mm/min and observed a continuous and even layer on the substrate. A primary current of 150 A or more can be used to overlay a uniform and continuous layer to the substrate by varying the welding speed. Higher contact angle and lower dilution were noticed at higher current and higher overlaying speeds. The increase in primary current increased the dilution and reduced the contact angle with lower bead width. In-depth microstructural examination exposed defect-free Inconel 625 hardfaced overlays with better metallurgical bonding at the interface. The overlay weld thickness varied in the range of 1.50–2.62 mm on the substrate. The hardfaced layers contain dendritic and interdendritic precipitates of Nb along the AISI 347 substrate. The intermetallic precipitates in the upper region of the overlaid weld are combined with columnar dendrites to form the Laves and (Nb, Ti) C phases. The EDS plots show the lower concentration of Fe in the IN625 overlay welds. EDS examination shows the Fe elemental dispersion and increase in the wt% of Fe in the partially melted zone of the substrate. The as-deposited overlay consists of Ni3Si, M23C6 and Ni3B phases. The micro-Vickers hardness of the hardfaced layers revealed the presence of HAZ in the substrate by GMAW process. At the applied load of 90 N, The wear rate increased with the increase in applied load on the overlaid welds from 20 to 90 N. The wear trend varies with applied load and wear time. The successfully deposited overlay welds can be suitable for worn surfaces and engineering applications to protect the stainless steels.

Microstructure and Characterization of Overlay Welding Layer using Fe-based Composite Powders

Microstructure and Characterization of Overlay Welding Layer using Fe-based Composite Powders

Properties of weld overlays on regenerated wheel hub of a mining vehicle

The paper presents problems related to the regeneration of wheel hubs for mining machinery vehicles carried out with arc welding using the MAG method. Hubs made of medium-carbon cast steel, type LII500, were weld surfaced with filler metal grade of G4Si. The tests were aimed at determining welding imperfections and metallographic properties of the surfacing welds. The influence of heat treatment on the properties of surfacing was investigated. Hardness distributions in welded hubs after various heat treatment operations were determined. Recommendations for the technology of weld surfacing the wheel hubs were formulated.

The Comparison of Cracking Susceptibility of IN52M and IN52MSS Overlay Welds

Overlay-welding of IN52M and IN52MSS onto CF8A stainless steel (SS) was conducted by a gas tungsten arc welding process in multiple passes. An electron probe micro-analyzer (EPMA) was applied to determine the distributions and chemical compositions of the grain boundary microconstituents, and the structures were identified by electron backscatter diffraction (EBSD). The hot cracking of the overlay welds was related to the microconstituents at the interdendritic boundaries. The formation of γ-intermetallic (Ni3(Nb,Mo)) eutectics was responsible predominantly for the hot cracking of the 52M and 52MSS overlays. The greater Nb and Mo contents in the 52MSS overlay enhanced the formation of coarser microconstituents in greater amounts at the interdendritic boundaries. Thus, the hot cracking sensitivity of the 52MSS overlay was higher than that of the 52M overlay. Moreover, migrated grain boundaries were observed in the 52M and 52MSS overlays but did not induce ductility dip cracking (DDC) in this study.

TIG 육성용접을 위한 모재 온도와 오실레이션에 따른 비드형성 특성에 관한 연구

오버레이 용접은 해양 플랜트 분야, 원자력 발전소 분야, 다양한 발전 설비, 중장비 및 대형 디젤엔진 등과 같은 많은 산업 분야에 적용되고 있다. 오버레이용접은 지속적으로 발전하고 있으며 그 수요 또한 계속해서 증가하고 있다. 따라서 높은 생산성과 고품질의 오버레이 용접이 요구되고 있다. 오버레이 용접에서 LF는 비드 겹침부에서 빈번히 발생하며 비드의 퍼짐성이 낮다는 것이 주요 원인이다. 비드퍼짐성이 좋지 않은 경우, 비드의 산골차가 커지는 외관결함의 문제와 LF와 같은 문제가 발생한다. 본 연구에서는 목적은 비드 퍼짐성의 특성을 파악하기 위해 C형 용가재를 이용한 TIG 용접으로 모재 온도와 오실레이션 증가에 따른 특성을 연구 하였다. 모재의 온도와 오실레이션 폭이 증가함에 따라 비드 폭은 비례하여 증가하는 결과를 나타내었다. 오실레이션의 폭의 특성에 따라 용입의 형태가 변하고 오실레이션폭이 커질수록 비드 퍼짐비는 1로 수렴하는 비드형성 특성의 결과를 확인하였다.

Ductility-dip cracking susceptibility in dissimilar weld metals of alloy 690 filler metal and low alloy steel

The effect of dilution ratio and chemical composition on the ductility-dip cracking (DDC) susceptibility of dissimilar overlay welds of Alloy 690 filler wire and low alloy steel (LAS) was investigated. We measured the hot ductility curve using a hot tensile test coupled with an in-situ measurement system. The minimum critical strain of Alloy 690 was 4.0% at 943 °C. The minimum strain and the temperature decreased with increasing LAS content from 3.2% (901 °C) to 2.4% (842 °C) and 2.2% (802 °C) at LAS contents of 25%, 50%, and 75%, respectively. The formation of tortuous grains resulting from microconstituents containing niobium improved the DDC susceptibility. With increasing dilution of LAS, the niobium content decreased, resulting in a reduction in the tortuosity ratio at the cracked grain boundaries. In addition, the grain boundaries embrittled with increased dilution ratio owing to an increased phosphorous and sulfur content. Therefore, at high LAS content, the combination of low tortuosity ratio of the grain boundaries and high phosphorous and sulfur content increases DDC susceptibility.

Metallurgical and mechanical investigations of Inconel 625 overlay welds produced by GMAW-hardfacing process on AISI 347 pipes

Inconel 625 is a widely employed material for hardfacing to protect components of aircrafts, oil refinery and power generation, possessing better corrosion resistance behaviour at high temperature applications. These characteristics are related with the hardfacing material composition and microstructure of overlaid welds which is influenced by the process parameters and the substrate composition of the component to be protected. Hardfacing has been extensively used for modifying surface and repairing. In this research, single bead overlays of Inconel 625 were deposited on the surface of AISI 347 pipe by GMAW process. Overlaid welds were deposited at three different heat inputs (0.48 kJ/mm, 0.53 kJ/mm and 0.59 kJ/mm) to synergic mode, while the voltage and wire feed rate are pre-programmed. The overlaid weld thickness varied from 1.5 mm to 2.62 mm on substrate with suitable overlaying parameters. This study was explored with Optical microscopy, Energy-dispersive x-ray spectroscopy (EDS), scanning electron microscopy (SEM), and mechanical tests were used for microstructural and mechanical characterization. The results showed that the overlay welds of Inconel 625 exemplified a noticeable microstructure upon solidification, while the bond interface can be observed and divided into distinct zones. Near the bonding interface, a non-mixed zone with precipitated ferrite of different formations were observed. The surface of overlaid weld microstructure to interface of substrate/weld overlay comprised of cellular, columnar and fine dendrites. An increase in Fe wt% in the partially mixed zone is corroborated to the melting and dispersion of the substrate. Uni-axial tension test and Vickers-micro hardness test were carried out on the specimen sectioned from overlay welds. The mechanical test responses revealed that the tensile strength and micro-hardness of the overlaid welds improved significantly compared to substrate. The mechanical properties of hardfaced area were better than bonding area and superior to substrate, revealing an excellent overlay weld deposition using Inconel 625.

Nitridation of grate in a biomass‐fired boiler

AbstractAfter a straw‐fired power plant in Denmark had been in operation for 16 years with 93,815 hr operation, there was a need for overlay welding repair of the grate due to a decrease in wall thickness from erosion/corrosion. The grate consisted of 15Mo3 (Werkstoff nr. 1.5415) tubes where water/steam flows through, which were welded together with fins, and where one side faced the combustion zone coming into contact with the fuel (the side that required weld overlay). The water/steam temperature was 320°C and the surface metal temperature was estimated to be 350°C. However, there were difficulties when trying to overlay weld the grate as the weld pool was unstable. The microhardness measurements on cross‐sections of the tubes revealed a higher hardness of the tube facing the combustion zone compared to opposite the combustion zone. In addition, there was higher hardness adjacent to the combustion side than the steam/water side. Analysis of etched cross‐sections with light optical and scanning electron microscopy revealed the presence of acicular structures at the convex surface. Further analysis has been conducted with X‐ray diffraction and a LECO nitrogen analyser indicating the presence of iron nitrides. Reasons for their evolution and implications for the repair welding are discussed.

Numerical Analysis of the Influence of Electrode Inclination on Temperature Distribution during GMAW Overlaying

In the work, an analysis of the influence of electrode inclination on the distribution of temperature in the weld overlaying has been conducted. In the analytical description of the temperature field, a volumetric heat source model with an inclined axis with respect to the direction of surfacing was adopted. In the numerical simulation, the own theoretical model of heat source, algorithm, and program performed in the Borland Delphi environment were used. In the calculation examples, different electrode inclination angles were adopted in relation to the welded plate, in the direction of surfacing, opposite to the direction of welding, and perpendicular to the weld bead.

A Study on Process Development of Deformation Reduction in TIG Overlay Welding

Overlay welding is a technique to obtain surface layer having a corrosion resistance or heat resistance. Because plant industry has developed, demand of overlay welding also increases. In the overlay welding, uninform heat cycle can cause a lot of welding deformation. Deformation of overlay welding has problems such as diminished dimensional accuracy and reduced product reliability. A lot of deformation is corrected in a number of ways. However, correction of deformation costs a lot of time and cost. Also correction of deformation requires skilled techniques. In addition, heat straightening produce a large amount of green-house gas and effect on global warming. In this study, the effect of welding process on the deformation was examined. The amount of deformation by the conventional TIG welding process and Super-TIG welding process was compared quantitatively. As a result, the amount of angular distortion was as follows: Conventional TIG > Super-TIG stringer bead > Super-TIG oscillation bead. It’s considered that the angular distortion by Super- TIG welding was small because heat input ratio of Super-TIG welding was low. Therefore, Super-TIG welding process has advantages in overlay welding because of low deformation and low dilution ratio. Key words: Angular distortion, TIG welding, Super-TIG welding, Overlay welding, Deformation, STS316L, Dilution ratio, Penetration

Operational behavior of the switchback GMAW process using a mechanized rig for arc movement

Switchback Gas Metal Arc Welding (GMAW) consists of a forward and backward periodic oscillation of the welding torch in the longitudinal direction of the joint. The present work has two objectives, to evaluate the use of a simple and practical device proposed for the switchback manipulation of the torch and to analyze the effect of the switchback parameters on the operational characteristic of the process. Two series of bead-on-plate depositions were planned, using the GMAW process with or without the switchback technique. To find an operational envelope, two levels of equivalent welding speeds were used for covering ranges of oscillation frequency and amplitude. A Ni superalloy was employed as deposition material, aiming at simulating weld overlays. Wire feeding speed, set voltage and contact tip-to-work distance (CTWD) were kept constant. The proposed device was evaluated and proved to be able to make the overlays with all combinations of planned parameters. It was demonstrated that if the backward length (B) is larger than half of the forward’s (F), the torch passes more often over the same point of the deposit, and the oftener the torch passes over the same point, the lower the incidence of intermittent narrowing of the bead. By evaluating the surface aspect of the beads, the greater the F, the higher the likelihood of this irregularity. Penetration is shallower with switchback (reason demonstrated based on the fraction of stroke length that the arc is over the subtract), yet the bead surface presents more ripples. Another incident non-geometric conformity is the "dragon back" aspect of the bead, which is favored by faster equivalent welding speeds and high values of forward and backward speeds. The found operational envelope for the GMAW process with switchback was stablished with low-values of speeds and lengths of forward and backward strokes.

The laboratory tests of hybrid layers combining hardfacing and nitriding dedicated to increase the durability of forging tools in hot forging processes

In response to the growing need to use wear-resistant layers that increase durability of tools in forging pro-cesses, hybrid layers have been proposed that combine hardfacing with nitriding treatment. This article presents the results of laboratory tests of surface wear-resistant layers made with a new hybrid technology Gas-Shielded Metal Arc surfacing (hardfacing) with ZeroFlow gas nitriding. Specimens made with hardfacing or nitriding were prepared and examined. Analysis covered the thorough microstructure study, EDX chemical composition analysis and microhardness analysis. In experiment, 3 different types of nitrided layers were proposed for alpha, gamma prim and epsilon nitrides in the surface layer. The results of metallographic research in the surface layer was presented. The analysis of chemical composition in the particular overlay welds was performed to determine the content of alloying elements in the particular overlay welds. The susceptibility to nitriding of used weld materials as well as the ability to form particular types of nitrides on selected welded substrates was also tested.

Low heat input gas metal arc welding for dissimilar metal weld overlays part III: hydrogen-assisted cracking susceptibility

Dissimilar metal weld overlays of nickel-base alloys on low-alloy steel components are commonly used in the oil and gas, petrochemical, and power generation industries to provide corrosion and oxidation resistance in a wide range of service environments and temperatures. Traditionally, dissimilar weld overlays are produced using cold or hot wire gas tungsten arc welding. This study aims to identify and evaluate potential advantages of low heat input gas metal arc welding processes over the conventional gas tungsten arc welding in the production of such overlays. Parts I and II of this publication series described characteristics of the heat-affected zone and the transition zone region of alloy 625 on grade 22 steel overlays. These results indicate a good resistance against hydrogen-assisted cracking, which is being verified within this third part of the publication series. To determine the hydrogen-assisted cracking susceptibility, welded samples are tested using the delayed hydrogen-assisted cracking test. Fractography is performed using scanning electron microscopy along with energy dispersive spectroscopy. The results confirm the suitability and efficiency of low heat input gas metal arc welding for dissimilar weld overlays. Variation of the postweld heat treatment procedure bears potential for improvement in this respect.

Performance of the INCONEL 625 alloy weld overlay obtained by FCAW process

Nickel-based weld overlays (cladding) are commonly used in oil & gas industry to extend the life of equipment under corrosive environment, as it improves the corrosion resistance without a significant increase in the manufacturing cost, when compared to a full nickel-based alloy equipment. Although there are extensive literature involving overlays applied by SMAW, GMAW or GTAW processes, works about the use of FCAW process are limited. Consequently, an investigation of the performance of the overlays deposited by this process, which provides a higher productivity in comparison to the processes usually used, can be an interesting option for this application. The present work evaluates the mechanical and microstructural properties of the nickel-based superalloy 625 weld overlay deposited on a ASTM A516 Grade 70 carbon steel plate by the flux cored arc welding process (FCAW), both in as welded and heat treated conditions. Bending and microhardness tests were performed in order to verify possible effects of welding thermal cycles on the mechanical properties. The microstructure was evaluated through both optical (OM) and scanning electron microscopy (SEM), with the use of electron backscatter diffraction (EBSD) technique. Corrosion tests were conducted on samples removed from the top layer of the weld overlay according to ASTM G 48 Method A. All results obtained with this welding process, in both as welded and heat treated samples, were considered satisfactory. Keywords: Clad; Inconel 625; FCAW; post weld heat treatment.

Microstructure, Mechanical and Corrosion Behaviour of Weld Overlay Cladding of DMR 249A steel with AISI 308L

Abstract Medium strength low alloy steel is an attractive material for naval and defence applications for its excellent mechanical properties. DMR 249A is extensively used for application of ship building for its superior mechanical properties but owes poor corrosion resistance. In order to overcome the corrosion problem, Weld overlay cladding is used as an effective technique which improves the strength and corrosion resistance but also helps in manufacturing lightweight structures. Aim is to combat the corrosion by weld overlay surface coating using conventional arc welding process and observe the dilution. In the current study, Weld overlay cladding on medium strength low alloy steel (DMR 249A) of 50mm thick is done using manual metal arc welding process (MMAW) with corrosion resistant austenitic stainless steel (308L) electrode. Two layers of coating were done one over the other (each 2mm thick). Weld overlay clads were characterized for metallographic studies to observe the microstructure changes using image analyzer attached to optical microscopy and scanning electron microscopy (SEM). Mechanical testing were carried out using micro vickers hardness tester andductility bend test using Universal Testing Machine (UTM). Pitting corrosion behaviour is determined by the potentio-dynamic polarization tests in acidic chloride environment. Inter Granular Corrosion (IGC) was performed in boiling copper sulphate solution as per ASTM A-262 for 15 hours duration. The present investigation established that microstructure studies revealed increase in δ-ferrite in the weld overlay cladding. Superior mechanical properties are observed in second overlay coating compared to first overlay coating and base metal. Pitting potential in second overlay coating is observed to be more positive when compared with first overlay coating due to increase in chromium content. IGC studies showed that first overlay coating with AISI 308L observed to be more sensitized and having more weight loss which tends to be highly susceptible than second layer coating. It is attributed to the formation of high amount of delta ferrite.

Study of Mechanical Behavior and X-Ray Elastic Constants of Nickel Alloy Weld Overlay

Study of Mechanical Behavior and X-Ray Elastic Constants of Nickel Alloy Weld Overlay

A method for evaluation of weld overlays exposed to combined wear and very high cycle fatigue conditions

Key machinery components used for diminishing, transporting or processing massive volumes of material in heavy industries are severely exposed to combinations of different wear mechanisms, like abrasion and surface fatigue. The microstructure and wear properties of state of the art iron based welding alloys used as surface protection do not only depend on the nominal chemical composition of the welding consumables and their manufacturing route, but also on the base material, variations in process technology and applied welding parameters. Commonly used wear and hardness and test or microstructural investigations are either cost and time consuming or do not provide a complete understanding about the material behavior of surface coatings exposed to combined wear including fatigue. Thus the aim of this study was to prove the concept of using ultrasonic fatigue testing as new method to understand and predict the behavior of welded surface coatings in a fast and reproducible way. Two flux cored wires from different manufacturing lines, but of the same nominal chemical composition were compared applying identical welding parameters. As a result, the two wires could be distinguished clearly by applying the ultrasonic fatigue test method.

Stellite Surfacing Technology

Currently, there are no methods for calculating the operating conditions of automatic submerged overlay welding (surfacing) with a sintered strip that would concider the features and technological parameters affecting the formation of weld metal. The dependences presented in the article indicate that the magnitude of the welding current has the greatest influence on the penetration depth, while the dependence on the voltage and the welding speed is insignificant. Accordingly, as the voltage increases, an increase in penetration occurs, but in the case of a surfacing rate, an inverse relationship is observed. The developed models are 95% adequate.An experiment was performed to determine the influence of the parameters of the overlay strip on the structure and properties of the weld metal.

High Temperature Erosive Wear Resistance of Overlay Welding Metal in Various Boiler Furnace Wall

High Temperature Erosive Wear Resistance of Overlay Welding Metal in Various Boiler Furnace Wall

A Study on the Characteristics of Laser Cladding Using the LC-190 Cemented Carbide Powder(I) - Characteristic Analysis of One-pass Clad Layer with Parameters -

Cladding is an alloy layer that is superior in abrasion resistance by spraying, overlay welding, laser cladding or the like on its surface in case of abrasion due to repeated abrasion, impact, corrosion. Laser cladding is a process in which a clad material and a part of a substrate are melted with a high power laser beam to form a coating layer completely metallurgically bonded to the substrate. In this study, laser cladding was performed using Co-based LC-190 alloy powder for hard facing of ship exhaust valve. One-pass cladding was performed by varying the preheating temperature, laser output and beam feed rate of the base material using a diode laser with a maximum output power of 8.0 kW. The shape, dilution rate, Characteristics were observed. As a result, defects could be suppressed by applying preheating, and as the heat input increased, the width of the clad layer increased and the height decreased. In addition, the average hardness value was gradually decreased as a result of hardness measurement, and it was found that dilution was increased by EDS component analysis. Key words: Hardfacing, Laser cladding, LC-190, Preheating temperature