Flux-cored Wire Research Articles

Wear Resistance and Characteristics of the Friction Surface of Metal Coatings with Nitride-Boride Alloying

The wear resistance and characteristics of the friction surface of metal coatings with nitride-boride alloying are investigated. The object of the study was the steel deposited with flux-cored wire containing 15% chromium, 0.5% boron nitride, 1.25% titanium di-boride and 0,5% zirconium di-boride. It was established that the average value of the relative wear per test was 0.00416 g/m, which is 1.8 times less than that of the coating metal without borides. The average value of linear wear was 0.0122 mm/m, which is 1,9 times less than that of the coating metal without borides. The average value of the friction torque for the entire friction path in 339 m was 20.96 Nm. The coefficient of friction was 0.425. The hardness of such a metal reaches a maximum value of 57 HRC. The micro-hardness of structural objects is for the matrix 617-648 HV, eutectic 764-847 HV and strengthening phases 1128-1247 HV. It is shown that the metal structure is an iron-chromium martensitic matrix with a eutectic component, formed on the basis of boride (Fe, Cr)2B and high-strength nitride ε-(Fe, Cr)2-3N, which is an effective obstacle to dislocation slip under conditions of plastic deformation of the surface at wear.

Application of X-ray diffractometry in the study of deposited metal with rare earth elements

The residual stresses in the weld metal and heat affected zone welded by experimental flux-cored wires (FCW) modified by rare-earth elements from the Tomtor deposit (Yakutia, Russia) were studied using X-ray diffraction methods. Alloy powders with 10 different concentrations of rare earth elements (REE) were designed and mixed with the filler material of UONI 13/55 covered electrode. The results showed that tensile internal residual stresses occurred in the weld metal and in the heat-affected zone with rare-earth metals. At the same time, compressive internal residual stresses were found in the weld metal and in the welded joint welded by flux-cored wire with 0.7 wt. % total content of REE, which prevent the formation and propagation of post-weld cracks. Microscopy indicated the formation of fine grain weld metal structure with increased hardness. There is a tendency to decrease the width of the heat-affected zone in all samples with REE compared to the heat affected zone (HAZ) width of the samples deposited by covered electrode. An optimal composition of flux-cored wires with a modifying additive with rare-earth metals is proposed.

Study on Residual Stress by Neutron Diffraction in SM570-TMC Welded by Flux-Cored Wires Containing Different Nickel

Study on Residual Stress by Neutron Diffraction in SM570-TMC Welded by Flux-Cored Wires Containing Different Nickel

Вплив складу шихтових матеріалів порошкових дротів на механічні характеристики та корозійну стійкість електродугових покриттів

The influence of charge materials of flux-cored wires on their mechanical characteristics, chemical microheterogeneity and corrosion resistance in an aqueous solution of 3% NaCl was established. It is shown that, in contrast to coatings made of solid wires, coatings sprayed using flux-cored wires (PO) have a high chemical heterogeneity. This is due to the fact that the droplets that disperse from the PD melt and form a coating have different chemical compositions. This is caused by incomplete fusion of the charge and steel shell at the ends of the PD during electric arc spraying of coatings. To reduce the chemical micro-heterogeneity, it is proposed to add powders of ferroalloys FeSi, FeMn and self-flux PG-10H-01 to the charge of powder wire containing chromium, boron, carbon-containing components (Cr, FH, PG-100, B4C, FCB) between the components of the charge, homogenize the melt of PD and, as a consequence, reduce the microheterogeneity of the coatings. The presence of chromium, ferrochrome, ferro-silicon and ferromanganese in the charge of PD 90Х17РГС and PD 75Х19Р3ГС2 determines the minimum chemical microheterogeneity of coatings from these wires and, as a result, ensures their high corrosion resistance, which is close to corrosion steel18. To increase the completeness of fusion of the components of the PD charge between itself and its steel shell, it is proposed to add to the PD charge powders of ferroalloys Fe-Mn, Fe-Si, which have a low melting point, able to interact with refractory components of the charge to form low-temperature eutectics. The addition of ferro-silicon, ferromanganese and self-flux alloy PN-10H-01 powders based on ferrochrobor and ferrochrome provided high hardness of electric arc coatings, low heterogeneity in terms of chromium content in coating lamellae and, as a consequence, high corrosion resistance.

Tribological properties and wear resistance of the metal deposited by chromium flux-cored wire with carbide-boride alloying

The wear resistance and the tribotechnical properties of chromium steel of the Fe-C-Cr-B system deposited by flux-cored wire with boron carbide alloyed were investigated. It is shown that this steel has high wear resistance. The average values of the mass wear of the deposited metal is 0.0028 g/m, and the linear values are 0.00723 mm/m. The average value of the friction moment was 21.82 N·m, and the coefficient of friction was 0.412. The hardness of such a metal reaches a maximum value of 58 HRC. The microhardness of structural objects for the matrix is 499-603 HV, for hardening phases is 859-924 HV. The metal structure is a martensitic matrix with a large number of reinforcing phases, formed on the basis of type carboboride (Cr, Fe)7(CB)3. It is shown that the mechanism of metal wear is associated with its high hardness due to the dispersed hardening by particles of compounds, which are effective obstacles to dislocation slip under conditions of plastic deformation of the surface during wear and a decrease in the role of the abrasive component of wear.

Corrosion properties of metal deposited by chromium flux-cored wire with boride-nitride-intrmetallic alloyng

The corrosion properties of the metal deposited with chromium flux-cored wire with boride-nitride-intermetallic alloying are investigated. It was established that the metal deposited with wire PP-Kh15+0.5%BN+1.25%TiB2+0.5%ZrB2 at the initial stage of corrosion behavior, estimated by the time until the first signs of corrosion appear, exceeds the metal welded with standard wire Sv-20Kh13 in 3.6 times, and long-term corrosion resistance 2.22 times. In this case, only a slight degree of etching of the matrix is observed in such a deposited metal, there is practically no dissolution of the boundaries of the boride eutectic, and the hardening phases do not undergo any changes, which determines the lower corrosion rate of such a coating. The powder wire PPKh15+0.5% BN+1.25% TiB2+0.5% ZrB2 can be recommended for surfacing wear-resistant coatings on parts of petrochemical equipment operating in an aggressive environment under abrasive wear.

Structural Features of Welded Joint of Medium-Carbon Chromium Steel Containing Metastable Austenite

Phase transitions during crystallization and subsequent thermal and deformation effects under the influence of various mechanical loads in welded joints of the plates of medium carbon steel by a consumable electrode in shielding gases with a flux-cored wire based on Fe–C–Cr matrix are studied. The test results for weldability, abrasive wear resistance, and stress state formation and the results of metallographic, electron microscopic, and X-ray diffraction studies are analyzed. It is shown that the structure of welded seam consists of metastable austenite, δ-ferrite, and high-strength carbon–chromium martensite. Welded joints have a high capability of intense hardening under local deformation owing to the TRIP effect (transformation-induced plasticity).

Study of the influence of the addition of an exothermic mixture and the ratio of the components of the exothermic mixture on the melting indices at FCAW

An important issue in the processes of strengthening and restoration of surfaces exposed to abrasive, abrasive-corrosive and hydroabrasive wear, using the process of self-protective flux-cored arc welding (FCAW), is to increase the productivity of hardfacing and the quality of the hardfacing metal. The literature review showed that one of the ways to increase the productivity of hardfacing and improve the quality of the hardfaced metal is to add an exothermic mixture to the core filler of flux-cored wire electrode. The effect of composition of filler core during FCAW on the fusion parameters, namely the addition of exothermic mixture (TM), the ratio of exothermic mixture components (CuO/Al), and the ratio of exothermic mixture oxidant to carbon content in the core composition (CuO/C) has been studied. It has been found that the optimum areas for the deposition rate (Gd), deposition factor (ad) and spattering factor (ψs) are observed for the following values of the core components: TM = 25…39, CuO/C = 5…6, CuO/Al = 3…4.

Mechanized surfacing of the end face of screw coils of a screw conveyor operating under abrasion conditions in a corrosive environment

The purpose of the work was to determine the possibility of the regenerative surfacing of the upper surface of screw conveyor coils. The screw conveyor, used for the transport of bulk materials in a corrosive environment, was originally surfaced with chromium cast iron. The research work discussed in the article resulted in the development of a MAG method-based technology enabling the repair surfacing of screw conveyor coils. The technology involved the use of an EnDOtec DO*11 flux-cored wire and required the previous removal of the hardened upper layer.

Rail surfacing repairing technique with self-shielded flux-cored wires

A newly self-protecting flux-cored wire was used for simulated U75V rail repairing and five welding process parameters were applied. The influence of welding parameter on the hardness and microstructure of the wire and solder layers was investigated. The single-pass welding process with different preheating parameters and post-treatment parameters were also taken into research. The results showed that the welding process parameters have a significant influence on the weld quality, and mismatched parameters will increase the welding defects. The number of welding layers has a great influence on the hardness and structure. Increasing preheating temperature and a post-heat treatment at a high-temperature can enhance the hardening effect.

Rare earth elements in self-shielded flux-cored wires and their effect on the weld toughing of U75V rail steel

Self-shielded flux-cored wire is a new type of welding material that has the advantages of outdoor and high-efficiency application, and it has been used widely for rail repair. A self-shielded flux-cored wire with high alkalinity and rare earth elements was taken for research, and the microstructure, inclusions, hardness and the impact toughness were studied. Rare earth elements could eliminate the oxygen and sulfur when they were added into the molten pool. The addition amount has been optimized to the range of 4% in the self-shielded flux-cored wire when used for rail repairing.

Effect of Ti element on the microstructure and properties of high chromium surfacing layer

The self-made high chromium content flux-cored wire was used to surfacing low carbon steel under self-protection. The effect of Ti contents on the microstructure, hardness and wear resistance of surfacing layer was investigated. The results showed that the surfacing layer was mainly composed of martensite, [Formula: see text] carbide and residual austenite. As Ti content in surfacing layer increased, the shape of carbides in surfacing layer varied from lath to granular and the amount of carbides was gradually increased. The hardness of the surfacing layer was slightly increased while the wear resistance was significantly enhanced. The improved wear property could be ascribed to the increasing Ti content and the corresponding increasing amount of Ti (C, N). Ti (C, N) takes the role of heterogenous nucleation particles in the surfacing layer and promotes the formation of fine-grained hard phase (e.g., [Formula: see text] carbide). With the increase of the density of fine-grained hard phase in the surfacing layer, the resistance of cutting motion during abrasive wear test also increased, resulting in a decreased wear loss and significantly enhanced wear performance.

Effect of Filler Si content on the Microstructure and Properties of Underwater Hyperbaric Welded Duplex stainless steel

Abstract Two flux-cored wires with 0.36% Si and 0.63% Si respectively were employed for this study. Welding using a type of wire with low Si content need one more weld pass than using the other type of wire with high Si content to fill the groove at a pressure of 0.45 MPa. The microstructures and mechanical properties of the welded metals were studied. The average austenite content was higher in the welded metal with low Si content than that in the welded metal with high Si content. More and larger inclusions were another important factor for the higher austenite content in the welded metal with low Si content. The excessive inclusions in the welded metal with low Si content decreased the grain sizes of ferrite and austenite and induced a greater number of special ferrite-austenite boundaries. Compared with the welded metal with high Si content, the welded metal with low Si content had more inclusions and a less pronounced solid strengthening effect, which deteriorated its mechanical performance. The hardness, yield strength, tensile strength elongation and impact toughness of the welded metal with high Si content were all higher than those of the welded metal with low Si content. Wire with more Si content could guarantee preferable microstructure, less inclusions and better comprehensive mechanical properties of the welded metal.

Structure and Tribological Properties of the Wear-Resistant Coatings Deposited Using Flux-Cored Wires Modified by Tantalum and Tungsten

Test flux-cored wires for arc spraying technology are developed. Tantalum and tungsten powders are selected as modifying additives. A PGSR-4 (Ni–Cr–B–Si) commercial powder is the basis of the powder material. The structure of the modified coatings is studied by metallographic analysis. Wear tests of the modified coatings are performed by slipping friction. The friction coefficients and the roughness characteristics are measured.

Thermodynamic Aspects of Cr2O3 Reduction by Carbon

In order to save chromium resources, technology of flux-cored wire surfacing is of great practical interest. In this case, Cr2O3 chromium oxide and carbon as a reducing agent are used as fillers. The thermodynamic probability assessment of 16 reactions between them under standard conditions, as well as for certain reactions under different standard conditions, was carried out using tabulated thermodynamic data of reactants in the temperature range of 1500–3500 K. The following were considered as standard states for reactants: Cr(ref) (reference state, melting point 2130 K, boiling point 2952 K), Cr(liq), Cr(gas), Cr2O3(cr, liq), Cr2O3(gas), C(ref), and as possible reaction products and standard states for them CO(gas), CO2(gas), Cr23C6(сr), Cr7C3(cr), Cr3C2(cr). The reaction probability was estimated using standard Gibbs energy and was calculated using the Van Goff isotherm equation. The chromium dissolution in metal of surfacing bath or probable partial pressures of CO and CO2 in gas phase was considered and then calculated from the equilibrium of carbon gasification reaction. The carbon presence in flux-cored wire with chromium oxide Cr2O3 as a reducing agent will necessarily lead to the occurrence of reduction reactions with chromium carbide generation, and possibly chromium itself. The generation of Cr7C3(сr) carbide is likely. With a longer life span of chromium oxide and carbon at a temperature above 2500 K, chromium generation as a component of the surfacing bath is more thermodynamically probable than carbide generation. Chromium oxide has the highest reactivity in Cr2O3(liq) state. Direct reduction is preferential. The generation of CO(gas) as a carbon oxidation product is more probable. The chromium dissolution in metal increases the thermodynamic reaction probability with its generation, as well as further reduces the reaction probability in which chromium is the starting material.

Wear resistance and characteristics of the friction surface of the coating metal with carbide-boride-nitride-intermetallic alloying

The metal deposited by flux-cored wire containing 15% chromium, 0.5% boron carbide, 0.5% boron nitride, 2.5% titanium diboride and 1.0% zirconium diboride was investigated. The hardness of such a metal reaches a maximum value of 58 HRC. The microhardness of the structural objects is 521-593 HV for the matrix, 829-978 HV for eutectics and 1262-1342 HV for reinforcing phases. It was established that the average value of the relative mass wear per test was 0.0034 g/m, and linear wear was 0.00862 mm/m, which is 2.2 times, respectively, and 2.7 times less than that of the coating metal without borides. The average value of the friction moment for the entire friction path of 452.16 m was 19.075 N⋅m. The coefficient of friction was 0.364. It is shown that the metal structure is an iron-chromium martensitic matrix with a eutectic component formed on the basis of boride (Fe, Cr)2B, having a frame structure, dispersed inclusions of (Fe, Cr)7(C, B)3 carboronides and high strength nitrides ε –(Fe, Cr)2-3N. High-chromium flux-cored wire alloyed by a complex of boron and nitrogen compounds provides a composite-type metal with high wear resistance and can be used for hardening the surfacing of parts operating under conditions of significant frictional loading.

Study of the properties of flux cored wire based on dust from gas cleaning plant of ferrochrome for surfacing on the cutting bodies of tunneling machines

The possibility of producing flux-cored wires based on dust from gas cleaning plant of aluminum production, silicon and aluminum powders (as a reducing agent) and gas cleaning dust from ferrochrome production (as a reducible component – chromium oxide) was studied. In the laboratory conditions samples of flux-cored wires were produced, surfacing, hardness measurement, abrasion rate and metallographic studies were performed.

Microstructure and mechanical properties of laser fusion welded Al/steel joints using a Zn-based filler wire

Laser fusion welding technique was used for lap joining of Q235 steel to AA5052 aluminum alloy using a flux-cored Zn-22Al filler wire. The influence of laser power on the microstructure and mechanical properties of laser Al/steel joints was investigated. A fusion welded region and a brazed region were formed at the fusion zone/steel interface: Fe2Al5−xZnx and FeZn10 were formed at the both regions, while a new FeAl IMCs with much lower hardness and brittleness was observed in the welded region. The phase constitutions at the both regions were unvaried with the change of laser power, while the phase morphologies were slightly changed. The tensile-shear testing results showed that the joint fracture load first increased then decreased with the rising laser power and the maximum value reached 1225 N at laser power of 2800 W. The joint fractured at the fusion zone/steel interface when the laser power was less than 2800 W and it changed into fusion zone when the laser power reached 3000 W. The change of joint fracture load and fracture behavior was mainly attributed to the change of morphology of IMC and interfacial bonding length.

Effect of Parameters Change on the Weld Appearance in Stainless Steel Underwater Wet Welding with Flux-Cored Wire

The underwater wet welding (UWW) technology is rapidly developing as a crucial method in the maintenance work of marine equipment and offshore platform. The rapid development of UWW technology has also exposed the problems to be solved urgently. Therefore, the influence of welding parameters on the weld appearance and welding spatters was investigated in this paper. The main welding parameters used in the study are welding current, arc voltage, welding speed and the contact tip-to-work distance (CTWD). Through the orthogonal test, it is found that, as each welding parameter increases within a certain range, the amounts of welding spatter decreases first and then increases, and the weld forming effect first becomes better and then deteriorates. The amount of wet welding spatter is mainly affected by the welding speed. When the welding speed is low, the splash is more, and the change of the welding current and the arc voltage has a little effect on the number of spatters. When the welding speed is large, the spatter is most with a small welding current and a large arc voltage. After evaluating the weld morphology obtained by welding under various parameters, a set of optimal parameters was obtained. The best parameters for the underwater wet welding of stainless steel with self-shielded flux-cored wire are determined to be 200 A-29 V-2.0 mm/s-15 mm (CTWD).

High variability in toxicity of welding fume nanoparticles from stainless steel in lung cells and reporter cell lines: the role of particle reactivity and solubility

Millions of people in the world perform welding as their primary occupation resulting in exposure to metal-containing nanoparticles in the fumes generated. Even though health effects including airway diseases are well-known, there is currently a lack of studies investigating how different welding set-ups and conditions affect the toxicity of generated nanoparticles of the welding fume. The aim of this study was to investigate the toxicity of nine types of welding fume particles generated via active gas shielded metal arc welding (GMAW) of chromium-containing stainless steel under different conditions and, furthermore, to correlate the toxicity to the particle characteristics. Toxicological endpoints investigated were generation of reactive oxygen species (ROS), cytotoxicity, genotoxicity and activation of ToxTracker reporter cell lines. The results clearly underline that the choice of filler material has a large influence on the toxic potential. Fume particles generated by welding with the tested flux-cored wire (FCW) were found to be more cytotoxic compared to particles generated by welding with solid wire or metal-cored wire (MCW). FCW fume particles were also the most potent in causing ROS and DNA damage and they furthermore activated reporters related to DNA double- strand breaks and p53 signaling. Interestingly, the FCW fume particles were the most soluble in PBS, releasing more chromium in the hexavalent form and manganese compared to the other fumes. These results emphasize the importance of solubility of different metal constituents of the fume particles, rather than the total metal content, for their acute toxic potential.