Hardfacing Deposits Research Articles

Hardfacing of 3.5% Chromium Cast Steel by Flux Cored Wire Arc Welding Process

Hardfacing weld is a technique which mainly improves and extends the useful life of engineering components. The purpose of this research is to improve welding procedure for one layer and three layers hardfacing of 3.5% Chromium cast steel and to study wear behavior of hardfacing layers. Flux Cored Wire Arc Welding (FCAW) process has been used as a welding process of this research by choosing austenitic stainless steel and martensitic hardfacing wire to weld the buffer and hardfacing layer respectively. Preheating was also used in this study. Abrasive wear test of hardfacing deposit were conducted in accordance with procedure “A” standard of ASTM G65. In addition, microstructures and macrostructure of worn surface deposits were analyzed by using optical microscope. These results showed that there is no crack and defect in the Heat Affected Zone (HAZ) and other regions. The hardness of preheating sample in HAZ regions was lower than the ones without preheating. Therefore, preheating samples should be done before welding. The abrasive wear resistance of three layers hardfacing deposit was better than one layer hardfacing deposit because one layer hardfacing deposit was more diluted from buffer layer than three layers hardfacing deposit. Moreover, weight loss of one hardfacing layer was also higher than three layers.

Effect of hardfacing on wear reduction of pick cutters under mixed rock conditions

A pick cutter is a rock-cutting tool used in partial-face excavation machines such as roadheaders, and its quality is a key element influencing the excavation performance and efficiency of such machines. In this study, pick cutters with hardfacing deposits applied to a tungsten carbide insert were made with aim of increasing their durability and wear resistance. They were field-tested by being installed in a roadheader and compared with conventional pick cutters under the same excavation conditions for 24 hours. The hardfaced pick cutters showed much smaller weight loss after excavation, and therefore better excavation performance, than the conventional pick cutters. In particular, the damage to and detachment (loss) of tungsten carbide inserts was minimal in the hardfaced pick cutters. A detailed inspection using scanning electron microscope.energy dispersive X-ray spectrometry and three-dimensional X-ray computed tomography scanning revealed no macro- or micro-cracks in the pick cutters. The reason for the absence of cracks may be that the heads of pick cutters are mechanically worn after the tungsten carbide inserts have been worn and damaged. However, scanning revealed the presence of voids between tungsten carbide inserts and pick cutter heads. This discovery of voids indicates the need to improve production processes in order to guarantee a higher quality of pick cutters.

Influence of laser surface melting on the characteristics of Stellite 12 plasma transferred arc hardfacing deposit

Stellite 12 hardfacing alloy deposited by plasma transferred arc (PTA) process on the 4140 steel substrate was subjected to laser surface melting (LSM) process. The effect of LSM on the PTA deposit was studied in terms of changes in microstructure and resultant variations in sliding wear properties. In the PTA state the microstructure, which consisted of Cr-rich (Cr7C3 and/or Cr23C6) and complex ((CoCrW)6C) carbides in Co matrix, was altered upon the application of LSM process. In short, LSM process led to the formation of a duplex layer, on the surface, consisting of carbide deficient and rich zones whose thickness tended to decrease with increase in the laser scan speed. As the result of formation of carbide rich zone at the outermost surface, LSM process provided an enhancement in surface hardness. On the other hand, the positive effect of LSM process on wear resistance became more apparent at high wear testing load causing carbide cracking and removal on the contact surface of Stellite 12 PTA hardfacing deposit.

Microstructure and Abrasion Resistance of Fe-Cr-C and Fe-Cr-C-Nb Hardfacing Alloys Deposited by S-FCAW and Cold Solid Wires

This work assesses the wear resistance behavior of different high Cr and Nb alloyed hardfacing deposits carried out by Self-shielded Flux Cored Arc Welding, considering the resulting microstructures as base for the analysis. To obtain non-commercial alloys, an “in-situ” technique was employed with addition of cold wire into the weld pool. Six combinations of two commercial FeCrC and FeCrNbC tubular wires and three different solid wires (AWS ER 70S-6, ER308LSi and ER 430) were used to obtain white cast iron hardfacing deposits on plain carbon steel subtracts. The welding parameters were identical for all combinations. Each deposit was characterized taking into account the resulting microstructure, hardness and abrasion wear resistance. The addition of a ferritic stainless solid wire in the weld pool resulted in the best wear resistance, which was boosted if Nb is present in the S-FCAW wire. The reason for these results was microstructure refinement and the presence of NbC and M7C3, the latter being present in all combinations.

Effect of Alloy 625 Buffer Layer on Hardfacing of Modified 9Cr-1Mo Steel Using Nickel Base Hardfacing Alloy

Dashpot piston, made up of modified 9Cr-1Mo steel, is a part of diverse safety rod used for safe shutdown of a nuclear reactor. This component was hardfaced using nickel base AWS ER NiCr-B alloy and extensive cracking was experienced during direct deposition of this alloy on dashpot piston. Cracking reduced considerably and the component was successfully hardfaced by application of Inconel 625 as buffer layer prior to hardface deposition. Hence, a separate study was undertaken to investigate the role of buffer layer in reducing the cracking and on the microstructure of the hardfaced deposit. Results indicate that in the direct deposition of hardfacing alloy on modified 9Cr-1Mo steel, both heat-affected zone (HAZ) formed and the deposit layer are hard making the thickness of the hard layer formed equal to combined thickness of both HAZ and deposit. This hard layer is unable to absorb thermal stresses resulting in the cracking of the deposit. By providing a buffer layer of Alloy 625 followed by a post-weld heat treatment, HAZ formed in the modified 9Cr-1Mo steel is effectively tempered, and HAZ formed during the subsequent deposition of the hardfacing alloy over the Alloy 625 buffer layer is almost completely confined to Alloy 625, which does not harden. This reduces the cracking susceptibility of the deposit. Further, unlike in the case of direct deposition on modified 9Cr-1Mo steel, dilution of the deposit by Ni-base buffer layer does not alter the hardness of the deposit and desired hardness on the deposit surface could be achieved even with lower thickness of the deposit. This gives an option for reducing the recommended thickness of the deposit, which can also reduce the risk of cracking.

Influence of the Hardfacing Welds Structure on Their Wear Resistance

The contribution presents the research results of hardfacing metals’ resistance in conditions of abrasive wear. Two types of hardfacing electrodes with a different chemical composition were used in the creation of three layers of hardfacing metals. The chemical composition of electrodes determines the difference in a hardface deposit structure. We have investigated the influence of mixing the base metal and a filler metal and the influence of hardfacing welds structure on the resistance against abrasive wear. The results of the experiments have showed that the intensity of wear is very dependent on the parameters of wear as well as the morphology structure of hardfacing metals.

Some studies on three-body abrasive wear behaviour of hardfaced steel alloy for agricultural plough tool application

The influences of hardfacing deposit and deep cryogenic treatment on three-body abrasive wear behaviour of AISI 1013 steel were studied. The three-body abrasive wear tests were carried out using the dry sand/rubber wheel test rig as per ASTM G65 standard. Hardfacing was done by manual arc welding using ZEDALLOY VB hardfacing electrode. The deep cryogenic treatment was carried by using liquid nitrogen temperature at −196°C. The applied load, sliding velocity and sliding distance were considered as process parameters. Experimental results reveal that the hardfacing deposit showed the highest abrasive wear resistance as compared to deep cryotreated material. Worn-out surface observation by SEM witnessed same behaviour. The nature of material removal was microploughing or microcutting depending on the attack angle, due to cracks formed on the surface of material.

Wear Behavior of Hardfacing Deposits on Hadfield Steel

The objective of this research was to develop the welding procedure for multilayer hardfacing of 13% Mn cast steel and study behavior of hardfacing deposits after impact applied. Austenitic stainless steel and martensitic hardfacing electrode were selected as buffer and hardfacing, respectively. Two different atmospheric conditions were compared which the first was controlling cooling rate on specimen by water during welding and another was un-controlling (by air), using shielded metal arc welding (SMAW) process. Macrostructure and microstructure were investigated by optical microscope. The hardfacing deposits were also determined by the dry sand rubber wheel machine according to procedure A of the ASTM G65 standard. The results indicated that the hardfacing layers revealed martensitic type microstructure in both controlled and uncontrolled cooling rate but their grain shapes were a little difference. For buffer layer showed austenitic type microstructure. And base metal layer presented amount of carbide in controlled cooling rate is less than in another one. The best wear resistance was obtained from controlled cooling rate condition.

Wear Behavior of Hardfacing Deposits on 3.5 % Chromium Cast Steel

The objective of this research is to develop the welding procedure for multilayer hardfacing of 3.5 %chromium cast steel and study wear behavior of hardfacing deposits. Austenitic stainless steel and martensitic hardfacing electrodes were selected as buffer and hardfacing, respectively. Four types of welding procedures were investigated, using shielded metal arc welding (SMAW) process. Three different preheatings were applied in this study. Characteristic of the macro, microstructure and worn surface deposits was investigated by optical microscope. The hardfacing deposits were also determined by the dry sand rubber wheel machine according to procedure A of the ASTM G65 standard. The results indicated that the multilayer hardfacing with and without preheating revealed no crack or defect in the Heat Affected Zone (HAZ) and other regions. The wear resistance of hardfacing presented a little difference. The best abrasive wear resistance was obtained from sample without preheating. This was due to the full martensitic microstructure of the hardfacing.

Study of magnetism in Ni–Cr hardface alloy deposit on 316LN stainless steel using magnetic force microscopy

Nickel base Ni–Cr alloy variants are extensively used for hardfacing of austenitic stainless steel components in sodium cooled fast reactors (SFRs) to avoid self-welding and galling. Considerable difference in the compositions and melting points of the substrate and the Ni–Cr alloy results in significant dilution of the hardface deposit from the substrate. Even though, both the deposit and the substrate are non-magnetic, the diluted region exhibits ferromagnetic behavior. The present paper reports a systematic study carried out on the variations in microstructures and magnetic behavior of American Welding Society (AWS) Ni Cr–C deposited layers on 316 LN austenitic stainless steels, using atomic force microscopy (AFM) and magnetic force microscopy (MFM). The phase variations of the oscillations of a Co–Cr alloy coated magnetic field sensitive cantilever is used to quantitatively study the magnetic strength of the evolved microstructure in the diluted region as a function of the distance from the deposit/substrate interface, with the spatial resolution of about 100nm. The acquired AFM/MFM images and the magnetic property profiles have been correlated with the variations in the chemical compositions in the diluted layers obtained by the energy dispersive spectroscopy (EDS). The study indicates that both the volume fraction of the ferromagnetic phase and its ferromagnetic strength decrease with increasing distance from the deposit/substrate interface. A distinct difference is observed in the ferromagnetic strength in the first few layers and the ferromagnetism is observed only near to the precipitates in the fifth layer. The study provides a better insight of the evolution of ferromagnetism in the diluted layers of Ni–Cr alloy deposits on stainless steel.

The effect of microstructure on high-stress abrasion resistance of Fe-Cr-C hardfacing deposits

Surface modification of mild steel was undertaken using two covered electrodes and two tubular electrodes. The two covered electrodes are DIN 8555: E6-UM-60 and E10-UM-60GR; however, the two tubular electrodes are E10-GF-60GR1 and E10-GF-60GR2. Chemical analysis for the weld metal and XRD of the flux covering for covered electrodes and flux core for tubular electrodes were conducted. The most important factor in determining the wear resistance is the microstructure of the deposit layers. In similar carbon equivalent electrodes E10-UM-60GR and E10-GF-60GR1, electrode E10-GF-60GR1 (tubular) shows larger carbides area fraction and better wear resistance than electrode E10-UM-60GR (covered). This could be attributed to a lower dilution associated with tubular electrode compared with covered electrode. The two tubular electrodes showed higher wear resistance than the covered electrodes which is mainly due to the larger Fe-Cr carbide precipitation area fraction.

The effect of microstructure on high-stress abrasion resistance of Fe-Cr-C hardfacing deposits

The effect of microstructure on high-stress abrasion resistance of Fe-Cr-C hardfacing deposits

Resistance of Hard-Facing Deposit Created by Laser Surfacing Technology

Presented study deals with the resistance of a surface layer created by laser surfacing. Hard surfacing metal powder of type UltrAloy 10611 with a 50 % share of tungsten-carbide particles was used for laser surfacing. Created weld was tested in laboratory conditions (hardness HRC) as well as in field soil conditions (relative wear resistance). Obtained results confirm that this added material is suitable for use in conditions where high abrasive wear is present

Microstructural and Mechanical Properties Investigation of TiC Reinforced Hardface Alloy Deposited on Mild Steel Substrate

Wear is one of the major problems faced in industry that reduces the life of industrial components and increases the operating costs. Therefore, hardfacing is widely employed by engineers to minimize components’ wear, in which single or multiple layers of hard material that mainly consists of carbides deposited on the base metal. However, these carbide-based materials suffer from solidification cracking due to lack of ductility. In this study, titanium carbide (TiC) reinforced alloy steel deposited using self-shielded flux cored arc welding technique. The microstructure and phase analysis in the hardfaced deposit by scanning electron microscope, energy dispersive x-ray and X-ray diffractometer revealed that the microstructure consists of finely distributed TiC within matrix of martensite and some retained austenite. Microhardness test and pin-on-disk wear test had shown that the clad deposit posses better hardness and wear resistance. Retained austenite formation and TiC precipitation were discussed in detail and correlated with the mechanical properties.

Non-Destructive Characterization of Nickel-Base Hardface Deposit on Austenitic Stainless Steel Through Eddy Current and Magnetic Barkhausen Techniques

Nickel-base Colmonoy (AWS ER NiCr) alloys find extensive application for hardfacing of austenitic stainless steel (SS) components in Fast Breeder Reactors. Gas Tungsten Arc deposited Colmonoy alloys suffer from significant loss in hardness and wear properties due to dilution from the austenitic SS substrate. In a multilayer deposit, dilution in first layer is highest and dilution decreases progressively in the subsequent layers. Although, both Colmonoy alloys and austenitic SS are non-magnetic, the deposit of Colmonoy on austenitic SS is ferromagnetic. The susceptibility to magnetic attraction in the hardface deposits is highest for maximum level of dilution and reduces with decreasing dilution. In the present study, Colmonoy-6 alloy co-deposited with austenitic SS filler wire, to obtain deposits with different levels of dilution, have been non-destructively evaluated by eddy current (EC) and magnetic Barkhausen (MB) techniques. The deposits were also characterized by microstructural and hardness studies. The EC parameters viz. magnitude and phase angle of the induced voltage showed an increasing trend with increasing dilution of the deposits. MB root mean square (RMS) voltage and peak height also indicated similar trend with dilution. The results produced from nondestructive tests could be correlated with hardness and microstructure of the deposits. Thus, it is possible to develop a non-destructive technique to predict hardness of the Colmonoy hardfacing alloy, which can serve as quality control tool in estimating the hardness of the hardfaced coating to ensure that dilution of the deposit by the substrate does not bring down the hardness of the deposit below the acceptable minimum values.

Influence of Carbon Content on Shock Hardening Behavior of Cobalt-Base Hardfacing Deposits

In this investigation, an attempt has been made to study the influence of carbon content on shock hardening behavior of cobalt-base hardfacing deposits for hot forging dies. The welding consumables with different carbon additions have been developed to fabricate the deposited metals by shielded metal arc welding (SMAW) process. Results show that the shock hardening effect and shock toughness of cobalt-base hardfacing deposit both are decreased whereas the hardness of the hardfacing layers is increased with the increase of the carbon content. All deposited metals contain Co-rich matrix dendritic structure with a network of Cr-rich carbides. After room temperature (RT) shocking, the density of the network of carbides increases to some degree and metallic compound NiW precipitates from the matrix. After 600°C shocking, NiW disappears from the matrix. For as-deposited, stacking faults and dislocation are found to exist in the matrix sporadically. After RT shocking, the formation of dislocation walls and dislocation cells are present as a result of hair-like dislocation locking effect, and the twin is observed. These conduce to the hardness and strength of cobalt-base hardfacing deposits.

Comparison of abrasive wear of a complex high alloy hardfacing deposit and WC–Ni based metal matrix composite

The abrasive wear of hardfacing deposits of a complex high alloy (SHS9290) and a tungsten carbide–Ni based metal matrix composite (MMC) has been compared using silica, garnet and alumina grit. In dry sand rubber wheel tests with silica abrasive and pin-on-flat tests with garnet abrasive, the SHS9290 alloy has shown a lower wear rate than the WC–Ni MMC. In comparison, in pin-on-flat tests using alumina abrasive, a higher wear rate was measured for SHS9290 alloy than the WC–Ni based MMC. The wear data has been interpreted in terms of the hardness of the constituent phases relative to the abrasives. The combination of high resistance to abrasive wear and known fracture toughness of SHS9290 alloy are optimal properties for digging picks used in ore excavation except with minerals of extreme hardness.

Effect of dilution and cooling rate on microstructure and magnetic properties of Ni base hardfacing alloy deposited on austenitic stainless steel

Nickel base Colmonoy 6 alloy finds application in hardfacing of various components made of austenitic stainless steel used in fast reactors. Gas tungsten arc deposited Colmonoy suffers from significant loss in hardness and wear properties due to dilution from the substrate. Magnetic property of the deposit is also influenced by dilution, and variation in magnetic parameters with dilution can be employed for non-destructive assessment of hardness in the hardfaced coating of the finished components. During hardfacing deposition, cooling rate may vary with deposition technique and process parameters. Development of a procedure for measurement of hardness of hardface deposit, irrespective of cooling rate, can prove to be useful for practical application. In the present study, the effect of cooling rate on microstructure, hardness and magnetic parameters of the Ni–Cr–B–Si hardface deposits is evaluated, and for coating cooled at different cooling rates, good prediction of hardness from its magnetic property could be obtained.

Estimation of Hardness in Nickel-Base Hardafacing Deposits on 316LN Stainless Steel by Magnetic Techniques

Nickel-base Colmonoy-6 (AWS ERNiCr) alloy is the material chosen for hardfacing of austenitic stainless steel (SS) components used in Indias’s Prototype Fast Breeder Reactor. Gas Tungsten Arc deposited Colmonoy hardfacing alloys suffer from significant loss in hardness and wear properties due to dilution from the austenitic stainless steel substrate. Although both austenitic SS and the undiluted Colmonoy-6 alloy are non-magnetic, the hardfacing deposit diluted by SS becomes ferromagnetic. In a multilayer deposit, magnetism is highest in the first hardfacing layer and decreases progressively in the subsequent layers. As in actual hardfacing deposits, dilution is difficult to control for any deposited layer, it is not easy to study variations of magnetic properties as a function of dilution. Hence, a separate set of deposits (twin-deposits) were produced by co-deposition of Colmonoy-6 alloy rods and austenitic SS filler wire on a copper block. Magnetic properties of hardfacing and twin-deposits were examined using Magnegage and Feritscope equipments. The saturated magnetic moments and Curie temperature of the twin-deposits were measured from room temperature to 873 K. Further, optical, scanning electron microscopy, energy dispersive X-ray spectroscopy and hardness measurements were performed for both hardfacing and twin-deposits. Correlation between hardness, microstructure and bulk magnetic property of deposits with different dilution levels could be established. It was also possible to correlate hardness with the magnetic property of the deposits. Thus, the present study indicates a potential use of magnetic techniques for estimating hardness and dilution of the Colmonoy hardfacing deposit in a component, which cannot be subjected to destructive examination.

Hardfacing of a Modified 9Cr–1Mo Steel Component Using a Nickel-Base Alloy

A dashpot piston made of modified 9Cr–1Mo steel is hardfaced with NiCr-B alloy by the Plasma Transferred Arc (PTA) process. During initial trials, a large number of cracks were observed in the hardface deposit when hardfacing was carried out directly on the modified 9Cr–1Mo steel substrate using a preheat temperature of 723 K. Both the deposit and the martensitic structure formed in the heat affected zone of the substrate during deposition are hard and hence were unable to absorb the thermal stresses generated, leading to cracking. Subsequently, hardfacing trials carried out with an intermediate layer of 2 mm thick Inconel-625 alloy, were successful and deposits were crack-free. Use of a relatively soft Inconel-625 between the hardface deposit and the substrate reduced martensite formation in the substrate, and thus the cracking susceptibility of the deposit.