Wear-resistant Hardfacing Research Articles

Microstructure formation in the powder HIPed hardfacing alloy Tristelle 5183 (Fe-21%Cr-10%Ni-7.5%Nb-5%Si-2%C in wt%)

Tristelle 5183 (Fe-21%Cr-10%Ni-7%Nb-5%Si-2%C in wt%) is an alternative material to cobalt-based alloys for wear resistant hardfacing applications. In this work, gas atomised powder was consolidated by hot isostatic pressing (HIPing) at 1120 ± 10 o C which is ∼ 100 o C below the melting onset point. The microstructure formation in the alloy, following densification, was investigated using X-ray diffraction, scanning and transmission electron microscopy and electron backscatter diffraction. The hot isostatically pressed (HIPed) alloy contains principally fcc γ -Fe, NbC, and M 7 C 3 with a small fraction of bcc α/δ -Fe and a π -ferrosilicide phase. This contrasts with the metastable gas atomised powder microstructure in which M 7 C 3 formation is largely suppressed and NbC precipitation is reduced. Following HIPing, a wide distribution of γ -Fe grain sizes is found. The larger grains exhibit sub-grain structures with significant intra-grain misorientations as identified by kernel average misorientation (KAM) maps. The smaller grains (< 10 μm) contain annealing twins, indicating that recrystallization had occurred only in certain localised regions which underwent sufficient plastic deformation in the early stages of HIPing. The work demonstrates the potential for HIPing hardfacing alloys to achieve a fine scale homogeneous microstructure. • HIPing homogenises the rapidly solidified powder microstructure of the alloy. • Insufficient recrystallisation of the powder results in a bimodal matrix grain size. • A mainly austenitic iron matrix contains NbC and M 7 C 3 precipitates. • M 7 C 3 is largely suppressed in the powder but precipitates out during HIPing.

Corrosion behavior of a wear resistant Co-Mo-Cr-Si alloy in molten fluoride salts

Evaluating the corrosion performances of wear resistant alloys is important for designing the molten salt-wetted bearings and valves in molten salt reactors. In this study, the corrosion behavior of wear-resistant Tribaloy T-400 alloy (Co-29Mo-8.5Cr-2.8Si) in molten FLiNaK salt (LiF–NaF–KF: 46.5–11.5–42 mol.%), with and without the presence of UNS N10003 alloy, were investigated through static immersion tests at 650 °C. After 400 h corrosion, T-400 alloy showed greater weight loss than UNS N10003 alloy, and the presence of UNS N10003 alloy further increased the weight loss of T-400 alloy. Electron microscopic and salt chemistry analyses showed that Cr and Co were selectively dissolved from T-400 alloy matrix after corrosion, resulting in a porous structure. On the other hand, the Laves phase precipitates were hardly corroded but showed signs of carbide formation on the surface. In addition, when tested with UNS N10003 alloy, some of the Co dissolved from T-400 alloy transferred to the surface of UNS N10003 alloy, hence promoted the corrosion of T-400 alloy. The results have indicated that even T-400 alloy has a relatively low Cr content among high temperature wear-resistant hardfacing alloys, its corrosion resistance is still inadequate in a typical molten salt reactor environment where UNS N10003 alloy and graphite are also present.

Circular economy practice: From industrial metal waste to production of high wear resistant coatings

Recently, recycling has become an essential issue in the industrial sector due to the soared consumption of materials and energy. One of the few possible ways to recycle metal waste is re-melting and converting the waste to new products. However, it requires a lot of energy, causes environmental contamination and is not applicable worldwide. Landfilling is no longer an option. This research paper focuses on finding an alternative way to recycle industrial waste by using the Submerged Arc Welding method (SAW) and metal waste, what is collected by manufacturing companies, in order to produce wear resistant hard-facings. When selecting metal waste, the greatest attention was given to waste of alloys with carbide forming elements. Turnings, shavings, and chips, as well as debris of high speed tool steel (HS6-5-2), ledeburitic high chromium cold work steel (X210Cr12), cast iron chips, waste of boron carbide B4C, worn grinding wheels (SiC), sintered hardmetal (H123, HG30) all were chosen as the remedy for reinforcement. Five possible compositions of above mentioned waste were discussed and tested on wear. SAW technique with properly chosen parameters: current 180–200 A, voltage 22–24 V, travel speed – 14.4 m/h was adapted for the production of hard-facings. Two methods to introduce waste metal powder to the weld zone were utilized: spreading of powder over the surface of substrate, and mixing with standard flux. Hard-facings obtained from waste materials were tested on abrasive emery wear. Volume-wear loss in most cases was compared to commercial steel grades. Wear results confirmed expectations as wear resistance of waste based hardfacings ∼2 times exceeded the wear resistance of commercial alloys.

Influence of niobium on the microstructure and wear resistance of iron-based hardfacings produced by pre-placement technique—a novel approach

This study introduces a novel approach to produce hardfaced alloys via pre-placement technique using the shielded metal arc welding process. The comparison between the microstructural, mechanical, and tribological properties of the Nb-free and Nb-additive hardfacings was characterized by optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray mapping, dry sliding wear, and hardness measurements. From the optical microscopy results, it was observed that the hardfacing alloys obtained by pre-placement technique with premixed powders are free of pores or cracks and show good metallurgical bonding with the substrate. SEM images revealed that the Nb-additive alloys are comprised of net-like carbides in interdendritic region and NbC particles in the matrix with a grain size ranges from 0.5–2 μm, which were found to be beneficial for enhanced hardness and wear resistance. Nb-additive alloy showed 2.63% increase in wear resistance in comparison with the Nb-free hardfacing. It has shown possible to obtain the high hardness and wear-resistant hardfacings with pre-placement technique.

Wear resistance and mechanisms of composite hardfacings at abrasive impact erosion wear

Tungsten carbide based hardmetal containing sprayed and melted composite hardfacings are prospective for protection against abrasive wear. For selection of abrasive wear resistant hardfacings under intensive impact wear conditions, both mechanical properties (hardness, fracture toughness, etc.) and abrasive wear conditions (type of abrasive, impact velocity, etc.) should be considered.This study focuses on the wear (wear rate and mechanisms) of thick metal-matrix composite hardfacings with hardmetal (WC-Co) reinforcement produced by powder metallurgy technology. The influence of the hardmetal reinforcement type on the wear resistance at different abrasive impact erosion wear (AIEW) conditions was studied. An optimal reinforcement for various wear conditions is described. Based on wear mechanism studies, a mathematical model for wear prediction was drafted.

FREIGHT AND PASSENGER VEHICLES PARTS RECONDITIONING TECHNIQUE

High accuracy and efficiency indices of machining of worn-out after continuous service parts, reconditioned using materials with high physical and mechanical properties have been studied; a reconditioning technique for worn-out surfaces of parts have been presented; to restore the dimensions of some parts, thermal spraying technique without inadmissible excessive heating of the parts has been chosen, and for another group of parts the process of manual argon-arc surfacing has been chosen; some specifications of the parts of the tram, trackless trolley bus, "KAMAZ", DT-75 tractor reconditioned by means of surfacing, coating and machining are given. Theoretical analysis of the conditions of the reduction of the elastic displacement value, appearing in a technological system during mechanical processing and determining the parameters of machining precision has been performed. Machining accuracy and efficiency improving features for grinding and cutting with cutting tools of parts with hardened (wear-resistant hardfacing materials with hardness up to HRC 63) function surfaces have been theoretically substantiated; some regularities of stock removal while grinding parts reconditioned using wear-resistant hardfacing materials have been analytically described, ways to improve the efficiency of their machining involving application of the method of deep grinding with the wheel periphery with rather low parts speed have been defined. Some ways to increase machining efficiency, to reduce energy consumption of machining and thickness of the cutting by grains of the wheel, and thus the wheel wear rate are presented. By means of calculations it was found out that realizing deep grinding of facing material, machining efficiency can increase by up to 8 times (with the same cutting thickness by a wheel grain) compared with the deep grinding of a solid (homogenous) material. Significant potential for grinding parts restored using wear-resistant surfacing materials, which opens new prospects for machining of resurfaced and face-hardened parts for freight and passenger vehicles, is shown. Potential for machining efficiency enhancement of the mentioned parts with cutting tools made of superhard synthetic materials, hard alloys with wear-resistant coatings, the use of damping cutters, and diamond-abrasive grinding is specified.

Application of titanium machining chips in welding consumables for wear-resistant hardfacing

Equipment of sugar cane plants and mineral extraction are submitted to severe abrasive wear conditions. Welded hardfacings are usually applied to repair this kind of damage, where commercial chromium/carbon-rich welding consumables have usually been employed. In the present work we investigated the microstructure of experimental hardfacings made by addition of residues (chips) collected from the machining of ASTM F67 (unalloyed Ti, grade 4) alloy. Mixtures with different carbide-formers (Cr/Nb ferro-alloys) were also tested. Two layers of ‘pure’ chips (Ti), chips plus Fe–Cr (Ti–Cr), and chips plus Fe–Nb (Ti–Nb) were applied on low-carbon steel specimens by the GTAW/TIG process. The microstructure of hardfacing layers was observed by optical and scanning electron microscopy (SEM) equipped with EDS microanalysis. The microstructural characterization has determined that carbide distributions change significantly with the chemical nature of the hardfacing. SEM observations coupled with EDS microanalysis have confirmed the formation of complex carbides within the metal weld, whose stoichiometry was determined by X-ray diffraction (XRD) analysis. Mixed carbides of MC type and some cementite have been found. As a result it was suggested that use of ASTM F67 chips as carbide formers for composition of welding consumables can contribute to improved wear resistance of hardfacings, if compared with traditional chromium-based hardfacings.

Hardfacing Corrosion and Wear Resistant Alloys

Hardfacing can be broadly defined as the application of a wear-resistant material, in depth, to the vulnerable (or worn) surfaces of a component by a weld overlay or thermal spray process.In the paper are presented the main hard facing iron-base and nonferrous alloys together with their properties and applications, together with a comparison of its performances.In addition, hardfacing alloys are applied to critical wear areas of original equipment or during reclamation of parts. These alloys, which are referred to as buildup alloys, are not designed to resist wear but to return a worn part beck to, or near, its original dimensions and/or to provide adequate support for subsequent layers of more wear-resistant hardfacing alloys.

Processing and wear of cast MMCs with cemented carbide scrap

Multiphase metal matrix composites (MMCs) which consist of recycled cemented carbide scrap and iron based matrices were produced, using different casting procedures, optimising the wear behaviour of these MMCs. The abrasive wear resistance of the MMCs was compared to different established materials for wear protection. Low stress abrasion tests were performed at room temperature and high stress abrasion tests at 500°C to characterise their wear behaviour at different stress and temperature levels. The manufactured composites show promising microstructural features with low level of dissolution effects and good metallurgical bonding of hard phases. Wear results point out that the developed cast MMCs show much better abrasion resistance than existing commercial wear resistant steels and are competitive to established wear resistant hardfacings at ambient and elevated temperature levels.

Wear Behavior of Weld Overlays on Excavator Bucket Teeth

An excavator is a typical hydraulic heavy-duty human-operated earth engaging machine tool used in general as a continuous digging machine in large-scale open pit mining operations. However, under dynamic loading, excavator bucket teeth are subjected to severe abrasive wear. The objective of this work was to improve the service life of the excavator bucket teeth in order to decrease the idle time required to reinstate the teeth periodically during excavation. This objective was carried out by overlaying the excavator bucket teeth (of high tensile steel) with four different wear resistant hardfacing alloys by manual metal arc welding. Comparative wear tests on a regular tooth and overlayed excavator bucket teeth were conducted in the field and laboratory (ASTM G-99, pin-on-disc apparatus), where the effect of hardfacing alloys on the extent of wear and the wear characteristics of the excavator teeth were examined.

Development of Hardfacing Alloys for Power Generation Applications

Abstract Development of wear-resistant hardfacing materials using powder metallurgy/hot isostatic pressing technology offers an alternative to today's cobalt-based materials and those that suffer delamination damage. Ongoing research and development at the Electric Power Research Institute (EPRI), detailed in this article, examines the application of wear-resistant hardfacing materials using the PM/HIP process. The hope is to eliminate weldability and residual stress challenges associated with some hardfacing alloys, as well as to provide a wider range of potential alloy solutions to reduce cobalt use and to address delamination issues with incumbent materials.

Microstructure and properties of Fe–Cr–C hardfacing alloys reinforced with TiC–TiB2

Different amounts of TiB2 powder were added to flux cores of wear resistant hardfacing flux cored wires for the preparation of new flux cored wires. Fe–Cr–C hardfacing alloys reinforced with TiB2 were produced by arc hardfacing. The microstructure, hardness and wear resistance behaviour of the hardfacing alloys were investigated using an optical micrograph, scanning electron micrograph (SEM), X-ray diffractometer, macrohardness tester, microhardness tester and abrasive wear tester. The results showed that, among the hardfacing alloys, a new hard phase, i.e. TiC–TiB2 composite compound particles, was formed and dispersed in the primary carbides and matrix structures. The TiC–TiB2 reinforced Fe–Cr–C hardfacing alloys imparted greater hardness and better wear resistance. The presence of TiC–TiB2 hard phase particles is the main reason for the improvement in hardness and wear resistance of Fe–Cr–C hardfacing alloys.

Room and high temperature wear behaviors of nickel and cobalt base weld overlay coatings on hot forging dies

The lifetime of dies used for production of forged parts is variable and determined by wear rate, plastic deformation, thermal and mechanical fatigue. These tools are subjected to extreme temperature at high unit pressures for short durations and must withstand multiple cycles while maintaining dimensional stability. This paper is an investigation into the use of nickel and cobalt base superalloys as wear resistant hardfacing materials on H11 tool steel. Three weld overlay alloys including Inconel 625, Stellite 6 and Stellite 21 were deposited on H11 steel substrates using tungsten inert gas welding (TIG) process. Wear tests were carried out using a pin-on-disk wear tester at room temperature and 550 °C. Microhardness of the weld overlays was obtained and the worn surfaces were examined by scanning electron microscopy (SEM). The results of the laboratory tests were then compared with the results obtained from field studies. The results showed a much lower wear at high temperature with the weld overlays due to formation of smooth compacted oxide layers on the wear surfaces. Inconel 625 showed the best wear behavior among the weld overlays at high temperature.

Microstructure and Hardness of High Cr Wear Resistance Materials Made by Ferro Materials

This study was performed to investigate the characteristics of the synthesized powder type ferro materials for wear resistant hardfacing. The powder type filler materials were made from ferro Cr and ferro Mn. Those ferro materials are two types, such as high carbon and low carbon contained. The alloy composed of high carbon ferro Cr and high carbon ferro Mn exhibited the best properties in terms of microstructure and hardeness for wear characteristics. Further, the alloys produced by the synthesized powders and wire type filler, were also evaluated in terms of microstructures and microhardness measurements. The results indicated that the synthesized powders displayed reasonable properties compared to commercial grade materials. The hardness value of the alloy produced by the synthesized powders were approached about 90% of the commercial grade`s hardness. The hardness values of the alloys closely depended on the amount of the dissolution of the ferro Cr, the hardness and the volume of the eutectic phase.

Study on the cavitation erosion behavior of hardfacing alloys for nuclear power industry

The cavitation erosion behavior of wear resistant hardfacing alloys for nuclear power industry Co-base Stellite 6 and new Fe-base alloy was investigated using 20 kHz vibratory cavitation erosion test equipment. Although the crack was initiated at the carbide-matrix interfaces, the matrix hardened by strain-induced phase transformation from austenite to martensite effectively repressed the crack propagation. The cumulative weight loss of new Fe-base alloy was about 2.40 mg/cm 2 after exposing to cavitation for 150 h and the cavitation erosion characteristic was similar to that of Stellite 6 on the whole range. The improved cavitation erosion resistance of new Fe-base alloy was due to the matrix hardening by the strain-induced phase transformation and to the small volume fraction of the carbide-matrix interface acting as crack initiation sites.

A novel procedure for fabrication of wear-resistant bushes for high-temperature application

Wear-resistant bushes, for high-temperature application, made of hardfacing alloys are required in various components for in-sodium service in the prototype fast breeder reactor (PFBR). For this purpose, bushes of Colmonoy 6, a nickel-base high-temperature wear-resistant hardfacing alloy, have been fabricated using a novel procedure involving weld deposition of the hardfacing alloy on austenitic stainless steel (SS) rods by the gas tungsten arc welding (GTAW) process followed by precision machining of the hardface deposits. Ultrasonic examination of the hardface deposits and the machined bushes, as also achieving the dimensional tolerance and surface finish on the bushes as per specification, confirmed the success of this fabrication procedure. Microstructural examination showed uniform distribution of precipitates throughout the thickness of the bush. The hardness obtained across the thickness and along the surface of the bush was well above the specified limit of 540 VHN (52 R C). Dimensional measurements after fabrication and thermal ageing at the service temperature of 823 K for 24 h and 1000 h confirmed dimensional stability of the bushes fabricated using the above procedure.

The Study on the Cavitation Erosion Behavior of Hardfacing Alloys for Nuclear Power Plants

The cavitation erosion behavior of wear-resistant hardfacing alloys such as Co-base Stellite 6, Fe-base Norem 02 and new Fe-base alloy were investigated up to 50 hours by using a 20kHz vibratory cavitation erosion test equipment. The crack, initiated easily at the interfaces between matrix and hard second phase, was repressed effectively in Stellite 6 because the matrix was hardened by phase transformation. For this reason, Stellite 6 showed an excellent cavitation erosion resistance compared to Norem 02. The phase transformation also occurred in Norem 02, but the increase of volume fraction of the interfaces caused the crack to be initiated frequently, thus resulting in a 1arge material loss. The matrix of NewAlloy was hardened effectively by vlongrightarrow<TEX>$\alpha$</TEX>' phase transformation and the volume fraction of the interfaces was very small compared to Norem 02. This caused the propagation of crack to the matrix to be repressed effectively. Therefore, NewAlloy showed a very excellent cavitation erosion resistance. It wasn't considered that the cavitation erosion resistance of NewAlloy was influenced the temperature of the bath filled with a distilled water up to <TEX>$80^{\circ}C$</TEX>.

Improving the reliability, durability, and efficiency of drill-rig shock absorbers with shell-type elastic elements

The technical-economic indices of deep-well drilling in hard, strong, and very strong rocks are improved by the use of drill-rig shock absorbers (henceforth referred to simply as shock absorbers). These devices reduce the vibrations of the drill rig, which in turn reduces the incidence of fractures of the heavily loaded drill pipes and the threaded couplings, lengthens the time between repairs of the bottom-hole engines, and makes it possible to optimize the service conditions of the bits. The use of such shock absorbers has a particularly significant effect on the technical-economic indices of drilling. The most important characteristics of any shock absorber are its durability and performance inside the well and the efficiency of its use. The reliability and service life of a shock absorber with shell-type elastic elements are determined by the durability of the parts of its housing, since the reliability and service life of the elastic element and the other parts are considerably greater. This circumstance is related to the operating conditions of the shock absorber: �9 the geometric dimensions of well are limited, which makes it impossible to maintain the necessary gap between the shock-absorber housing and the wall of the well, assuming that the shock absorber itself is of the necessary strength; �9 poor cleaning of the bottom of wells leads to the accumulation of abrasive sludge in the bottom region and along the well: �9 the shaft of wells is curved, and constrictions and projections are formed; �9 wells contain metallic and hard-alloy fragments of the teeth of the bits, as well as entire teeth tom from the cutter during drilling. All this creates very difficult conditions for the operation of the housing parts of shock absorbers [1, 2]. Thus, special protection must be provided to ensure their reliability, durability, and efficiency during the drilling of wells. In shock absorber installed on the shafts of motors, it is best to combine the housing of the shock absorber with the housing of the radial-thrust bearing of the turbodrill, electric drill, or screw motor (or the so-called spindle). This prevents vibration of the housing and its parts in an abrasive medium [3]. During rotary drilling, it is impossible to keep the shock absorber from also rotating. In this case, it is necessary to resort to technological and design solutions to protect the parts of the shock-absorber housing. Figure la shows a shock absorber with straight ribs equipped with hard-alloy inserts (teeth) or a wear-resistant hard facing [4]. It can be seen that the ribs are secured to a thick-walled adapter and a bushing, and the ends of the ribs overlap the thrust ends of the conical threads. Those threads are the most vulnerable and most dangerous parts from the viewpoint of the strength of the shock absorber. If the strength of the housing is increased (with its wall being at least 17.5 mm thick), the ribs can be attached directly to the housing (see Fig. lb). The ribs of the shock absorber can be made in helical form [5]. This reduces the number of ribs located about the perimeter.

Low Stress Abrasive Wear Behavior of a Hardfaced Steel

A plain carbon steel was overlayed with a wear-resistant hardfacing alloy by manual arc welding. Low stress abrasive wear tests were conducted with an ASTM rubber wheel abrasion tester using crushed silica and as the abrasive medium. The wear rate decreased with sliding distance, and there was an overall improvement in the abrasive wear resistance as a result of overlaying. The wear behavior of the samples has been discussed in terms of microstructural features while the examination of wear surface and subsurface regions provides insight into the wear mechanisms.

Wear-resistant hardfacing with powder wire

Wear-resistant hardfacing with powder wire