Papers by Keyword: Hardfacing

Abstract: Using high-strength steels as substrates for hardfacing has become more and more influential over the years. The usage of high-strength steels started with S690QL steel, but nowadays the S1100QL is also applied as a substrate. Several applications can be found in the construction and demolition fields where the dynamic loading occurs beside the abrasive loading. To withstand this complex loading, the high-strength steel substrates are hardfaced by special welding wires with good wear resistance. In case of welding this type of material requires pre-heating especially for thick plates and requires very strict welding technology and necessary to adjust the right t8/5 cooling time for good results. The pre-heating can be very costly in case of hardfacing because of the relatively large surfaces and production time is also increasing. Additionally, in case of S1100QL steel, only softening happens in the heat-affected zone, and in most cases, it is necessary to minimize this effect to reach the highest strength. Previous investigations highlighted the effect of heat input on the softening, but pre-heating is always applied. Recent research focused on the need for pre-heating during hardfacing on S1100QL steel. Specimens were made with and without pre-heating using the same technological parameters and circumstances. Macroscopic and microscopic tests were performed on the hardfaced specimens to check the dimensional and microstructural differences. Then Vickers hardness measurements are performed on several points which resulted hardness maps on both cases. The subzones of heat-affected zones are identified with the help of hardness maps, and a comparison was made. The hardness results show remarkable differences in different subzones between the pre-heated and not pre-heated specimens. Hardened parts are not found in the heat-affected zones, but less softening happens with the not pre-heated technology.

Abstract: Welding in general is a production process of joining metals that is carried out in a hot state. One of the welding developments in additive manufacturing is hardfacing. Hardfacing is one of the efforts that can be made to improve the mechanical properties and wear resistance of materials that allow them to be used in all conditions. Some of the problems found in ship companies, especially on ship hulls, are a decrease in mechanical properties and wear due to external factors such as damage to the hull due to waves. This research was conducted to determine the amount of mechanical properties produced in welding using the hardfacing process. In this study, the hardfacing method is used as the addition of weld metal to ASTM A36 plates using the SMAW welding method with angle variations. Furthermore, it will be analyzed by tensile testing to determine the tensile strength of the test specimen. In the process, material with a thickness of 5 mm is then welded by the SMAW method to the hardfacing process steel plate using a 3.2 mm E7018 electrode with the addition of 5 mm weld metal. The results obtained from tensile testing with high mechanical properties are found at the highest angle variation with good tensile test results and continue to increase from the lowest angle variation. This research can produce materials that can be used in companies as new materials with high mechanical properties.

Abstract: In the case of hardfacing the usage of high-strength steels is more and more influential. Several applications can be found in the construction and demolition fields where the dynamic loading occurs beside the abrasive loading. Additionally, the applied steel strength is increased, and S690QL and S960QL base materials are used as base materials for hardfacing. These materials are quenched and tempered which means that the heat cycle of the welding / hardfacing can cause significant changes in the heat-affected zone. The heat cycles of hardfacing have a different effect on the heat-affected zone, than the welding. Additionally, there are sub-zones where 2 or 3 heat cycles cause softening or hardening due to microstructural changes. The properties of the heat-affected subzones basically depend on the heat input, the number of heat cycles, and the base material. In this research, the hardness of heat-affected zones was investigated in the case of S690QL and S960QL base material. Hardfacing was made by different heat inputs in the case of both materials and after comparison, differences are written. One butter layer and 3 hardfacing layers were made in each case by robotic MIG/MAG welding. Several heat-affected subzones are determined, so for exact results hardness maps were made in all cases by hundreds of hardness tests. These maps show perfectly the differences between the hardness of the zones and the differences between the dimensions of heat-affected zones. There are significant differences in the multiple times heated subzones according to heat input. In the case of S690QL, the hardening is more significant than the softening in the heat-affected zone, the S960QL shows the opposite reaction to the heat cycles of hardfacing. On the hardness maps, the differences between the hardfacing layers are almost visible, and it shows big drops in the hardness of these layers in all cases.

Abstract: The application of high-strength steels is increasing rapidly nowadays, and steels with more than 1000 MPa yield strength are usually used in welded structures. The welding of these materials has many difficulties, so very important the precise technology planning, and disciplined work during welding. The weldability of these materials is commonly investigated field in case of joining. The application of ultra-high strength steels expands rapidly, and in the last years, it started to use them as a base material for hardfacing. Besides the wearing, there is a claim about higher strength of base materials in case of relatively extremely loaded machines. Because this ultra-high strength steel appears as a base material for hardfacing and it brings new challenges for welding technologists. In case of joining, the welding technology is complicated, usually need preheating before welding, is important to calculate and to use the right t_8/5 cooling time, and basically necessary to decrease the heat input as much as possible. The bad effect of welding heat input can be compensated by the filler material too in some cases. In contrast in case of hardfacing the base material itself usually has a big thickness, and no joint preparation, additionally important to reach deep fusion on the surface. It basically determines the heat input which has a different heat cycle as in case of joining. Therefore, the heat affected zone (HAZ) differs from the HAZ in case of joining application. In this investigation, four different hardfacing were made with four different technological parameters by robotic gas metal arc welding on S1100QL steel. During the welding parameter determination, we try to find a series of heat inputs from the lowest to the practically usable highest heat input. For the experiments, two filler materials used, one for the buffer zone, and for the hardfacing itself. Microstructural evaluation and hardness tests were made on the specimens which can show the differences between the heat affected zones.

Abstract: The aim of this study is to investigate the effect of applying various welding current parameters of shielded metal arc welding (SMAW) on microstructure and the hardness of the hardfacing overlays. The investigation was performed on a 12mm thick ASTM A36 steel plate weld overlaid by hardfacing electrode HV-450 of 3.2 mm diameter at various welding currents, 90, 110, and 130 amperes, respectively. The investigation was conducted by using optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and hardness test on the hardfacing overlay. The results showed the hardness of the hardfacing overlay is higher than the base metal, indicating higher strength of the weld overlay. From the three welding currents applied, the highest hardness in the weld overlay is obtained at the lowest current.

Abstract: The article aims to comprehend the microstructural changes, in Plasma Transfer Arc (PTA) deposited M2 high speed steel (HSS) hardfacings upon incorporation of 10 wt% Mo alloying during deposition followed by laser surface melting. PTA deposited hardfacings were produced over 4140 steel. Then Mo alloyed and unalloyed PTA deposits were subjected to laser surface melting (LSM) process. A comprehensive microstructural characterization for all the resultant structures was carried out. Optical metallography using appropriate etching reagents and SEM microscopy in conjunction with XRD techniques were employed to ascertain the matrix structure and carbides morphology. The PTA microstructure was close to equilibrium structure of M2 HSS containing mixture of ferrite/austenite/martensite along with MC, M₂C and M₆C type carbides. While the LSM of M2 HSS caused higher fraction of martensite and finer grains in the structure resulting in increment in hardness. 10-wt% Mo addition changes the carbides from MC and rod like M₂C to fibrous M₂C and fishbone like M₆C carbides. The LSM of Mo alloyed M2 HSS PTA deposits led to an overall decrease in the fraction of M₆C carbides and fibrous M₂C carbides accompanied by a decrease in hardness.

Abstract: This work studies the surface welding parameters for a practical repair for pearlitic rail grades: R260 and R350HT. A filler metal containing low carbon (0.15 %), high silicon (0.5 %) and nickel (2.5 %), self-shielded flux-core welding electrode (FCAW-S) is the candidate in order to ensure the preferable carbide-free bainite. The film-like morphology of the retained austenite is reported to promote the wear resistance and is ensured by silicon and nickel. The effect of preheat temperature and dilution on the microstructure and resulting hardness can be concluded. Too high dilution, as a result of high current and travel speed, and the reheating during the welding of the second layer can result in martensite formation and too high hardness. Proper control of the dilution ensures satisfactorily hardness and avoids martensite formation.

Abstract: This work presented the hardfacing process of high-strength structural steel based on JIS G3106 standard grade SM490YA by semi-automatic flux-cored arc welding with a dual shielding process of flux-cored self-shielded and protective gas-shielded (FCAW-G). In the welding process, the surface of SM490YA specimen was hardfacing welded by metal cored wire based on chromium carbide which was in standard of 8555: E10-MF-65-G. The hardfacing welds from FCAW-G and traditional self-shielding FCAW (FCAW-S) with and without preheat were inspected by visual and penetrant tests for evaluating the welding quality. The macrostructure of the deposited layer was investigated by optical microscope and image analysis for analyzing the weld penetration and weld dilution. In addition, the hardness of the hardfacing welded specimens was tested for the evaluation of the surface durability of the welded SM490YA.

Abstract: This study addresses characterization of ED (electrode drying) effect on WC hardfacing welding microstructure. Medium carbon steel blade which used as CD (continuous digester) blade to mix up sulphuric acid together with ilmenite ore in a digester tank as a major part of production. Microstructure of WC hardfacing, elemental composition alongside hardness analyses are executed to investigate the effect of ED (electrode drying). The ED (electrode drying) effect on microstructure and hardness values of WC hardafcing coating are characterized by SEM (scanning electron microscope) analysis and micro-Vickers hardness tester correspondingly. Results revealed that ED (electrode drying) effect less significant in the larger carbides at overall coating zone. However, the absence of ED (electrode drying) led to distribution of uniform smaller carbide in non-carbide zone. The uniform carbide distribution increases the hardness of the WC hardfacing coating.

Abstract: A grapple is a device that includes at least one gripping arrangement. The gripping arrangement is configured to grip and traverse objects so as to reach a desired location on site and to anchor it, therefore allowing the work to be carried out. [1] A method for controlling the fill volume of a grapple, such as a bulk-material crane grapple which includes at least one hoist-and-closure unit, may include adjusting the fill volume of the grapple is during the grapple closure process by adjusting/controlling the grapple hoist height. The grapple hoist speed and/or grapple hoist height may be the controlling parameter for the adjustment of the fill volume of the grapple. [2]Grapples geometric configuration is established by calculating the useful load mass. In the experiments performed in the present paper the load mass was 3000 kg. In exploitation, in cases where relatively low density materials, if compared to standard materials, are being moved/processed, changes to the volume capacity must be done; [3] changes that need to be correlated with the new materials and the exploitation conditions.The tractor attachment is a grapple assembly, and the grapple assembly kit includes a mounting assembly, a plurality of clamping units, and a plurality of support units. [4] A connection system for coupling an claw to a work vehicle includes a receiver assembly that needs to be implement and configured to a connector assembly of an arm of the work vehicle. [5]The solution developed by the authors consists in prolonging and consolidating the active elements of the grapple, by equipping it with additional elements that take and process load tensions, in the present case hard wood logs; and a consolidation and protection system that protects it from wear, that mostly appears when the hook crane repeatedly hits the ground in order to collect the deposited logs.The additional elements for handling and processing logs are made out of low alloyed steel, thus by configuring the tips we assure the good gliding of processed materials on the active/used surfaces. The self-protection system to wear is made out of boron micro-alloyed steel sheets that have hardness values up to 500 HB. Joining the grapple ensemble with specialized elements was performed through welding.