Fe–24wt.%Cr–4.1wt.%C hardfacing alloy: Microstructure and carbide refinement mechanisms with ceria additive

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.

Effects of Ce doping on mechanical properties of M7C3 carbides in hypereutectic Fe–Cr–C hardfacing alloy

The effect of microstructure on abrasive wear of a Fe–Cr–C–Nb hardfacing alloy deposited by the open arc welding process

In order to improve the mechanical properties of the wear-resistant layer of the hob cutter ring in shield construction, the influence of different composite matrix powders on the comprehensive performance of the cladding layer was investigated. In this study, TiC-reinforced Fe-Ni-based cladding layers with different matrix compositions were prepared on a modified H13 steel base material using plasma cladding (PC) technology. The matrix powders included Ni-based alloy powder, iron powder Y, and iron powder R. The two iron powders were mixed in different proportions, and then an equal amount of Ni-based alloy powder and TiC ceramic particles were added to form five kinds of composite cladding layer alloy powders. The cladding layers of five different matrices were obtained by cladding. The microstructure and mechanical properties of the composite cladding layer were studied using a metallographic microscope (OM), an X-ray diffractometer (XRD), a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), an electronic universal testing machine, an image processing microhardness tester, and an abrasive belt friction and wear testing machine. The results showed that the cladding layers of different samples had good metallurgical bonding with the base material. And the microstructure gradually refined from the bottom of the cladding layer to the top of the cladding layer. The cladding layer phases were mainly composed of Fe, FeO, TiC, FeNi, and CrNi. With the increase in the iron powder R ratio, the aggregation of alloy elements gradually alleviated. The ratio of iron powder R was increased from 1/10 to 2/5, the longitudinal shear strength between the cladding layer and the matrix was increased from 318 Mpa to 333 Mpa, and the transverse shear strength was increased from 303 Mpa to 342 Mpa. The hardness of the modified wear-resistant layer was better than that of the cladding layer without iron powder R, but the hardness of the cladding layer gradually decreased. After the modification of iron powder R, the wear resistance of the cladding layer was improved to varying degrees. When Y:R was 9:1, its wear resistance was the best, and the change trend of the wear resistance was consistent with that of hardness. The wear forms of different samples were adhesive wear and abrasive wear. And the height difference of the wear surface gradually increased with the improvement in wear resistance.

Effect of Ta on the microstructure and hardness of Stellite 6 coating deposited by low power pulse laser treatments

Nitrogen alloying of Fe–Cr13–C hardfacing alloy produces marked precipitation strengthening to achieve an improvement in high‐temperature wear resistance. Two hardfacing alloys of Fe–Cr13–C (with and without nitrogen) are slid on carbon steel at high‐temperature of 600°C and high load of 600 N, and wear behaviors are studied systematically. It is found that abrasive wear occurrs on the surface of the hardfacing alloy due to abrasive action of crushed oxide particles coming from the surface of carbon steel on the high temperature. The wear resistance is determined by the size and distribution of precipitates. The results show that the hardfacing alloy can obtain a great increase in hardness and a marked decrease in wear depth of grooving due to the effect of carbonitirde precipitates. The high‐temperature wear resistance of the Fe–Cr13–C hardfacing alloy is improved by nitrogen alloying, and the wear mechanism is mainly plastic deformation with minimum depth of grooving caused by the oxide particles.

The microstructure of the heat affected zone (HAZ) and fusion zone (FZ) in the as-welded condition of a single-pass weld performed by the flux-cored arc welding (FCAW) process was studied in a P91 steel using microhardness measurements, field-emission scanning electron microscopy, transmission electron microscopy, and x-ray diffraction. The evolution of precipitates in each region of the single-pass weld was analyzed, and particular attention was paid to the presence of retained austenite (RA). Experimental observations indicated that M23 C6 carbide played a major role in the thermal cycle associated with the weldment. On one hand, the dissolution of M23 C6 led to the precipitation of spherical NbCN in the finegrained HAZ (FGHAZ) near the coarse-grained HAZ (CGHAZ). On the other hand, the total or partial dissolution of M23 C6 carbides changed the chemical composition of the initially formed austenite. In the regions where the M23 C6 carbides were completely dissolved (i.e., the CGHAZ and FZ), retained austenite was observed as a thin, continuous film along primary austenite grains and lath boundaries. Instead, a shell of retained austenite was observed around some partially dissolved M23 C6 of the intercritical HAZ (ICHAZ) and FGHAZ.

Stellite 6, Colmonoy 56, and SKS3 tool steel are typically the materials used as weld hardfacing claddings or as-cast to provide the needed wear resistance to a base material with the required mechanical properties. In this study, a series of Co- and Ni-based hardfacing alloys are successfully fabricated on a substrate of S45C carbon steel using the plasma transferred arc process with Stellite 6 and Colmonoy 56 powders. An Fe-based hardfacing alloy is used on commercial SKS3 tool steel for comparison. The microstructure, hardness and wear resistance of the three materials are investigated systematically. The two claddings and the as-cast SKS3 examined belong to the categories of Co-, Ni- and Fe-based hardfacing, respectively, with hard carbides/borides in their microstructures. The two different claddings are not only tested against SKS3 tool steel but also against each other using the ring-on-disk wear test. After the wear test, the worn surfaces are examined using scanning electron microscopy and energy dispersive spectroscopy to identify the dominant wear mechanisms. The experimental results show adhesive wear is confirmed by metal transfer from a hard surface to a softer one in Stellite 6 against SKS3, and in Colmonoy 56 against the Stellite 6 specimens, while surface deformation testifies to abrasive wear. The transfer layer formed on the surface prevents direct metal-to-metal contact and reduces the wear loss. For Colmonoy 56 against SKS3, adhesion does not occur; instead, Colmonoy 56 causes serious abrasion on SKS3 due to its greater degree of hardness and causes significant wear loss for SKS3.

Abrasion resistance of Fe–Cr–C coating deposited by FCAW welding process

An analysis of common reinforcement methods of machine parts and theoretical bases for the selection of their chemical composition were carried out. Prospects for using flux-cored arc welding (FCAW) to restore and increase the wear resistance of machine parts in industries such as metallurgy, agricultural, wood processing, and oil industry were presented. It is noted that conventional series electrodes made of tungsten carbide are expensive, which limits their widespread use in some industries. The scope of this work includes the development of the chemical composition of tungsten-free hardfacing alloys based on the Fe-Mo-B-C system and hardfacing technology and the investigation of the microstructure and the mechanical properties of the developed hardfacing alloys. The composition of the hardfacing alloys was developed by extending the Fe-Mo-B-C system with Ti and Mn. The determination of wear resistance under abrasion and impact-abrasion wear test conditions and the hardness measurement by means of indentation and SEM analysis of the microstructures was completed. The results obtained show that the use of pure metal powders as starting components for electrodes based on the Fe-Mo-B-C system leads to the formation of a wear-resistant phase Fe(Mo,B)2 during FCAW. The addition of Ti and Mn results in a significant increase in abrasion and impact-abrasion wear resistance by 1.2 and 1.3 times, respectively.

This study shows the effect of Fe-based hardfacing alloy deposited by GMAW on low carbon steel substrate on the microstructure and wear resistance. Optical microscopy and scanning electron microscopy were performed to examine and evaluate the microstructure of hardfacing alloy. Also, pin-on-disc wear test was performed on the weldment and wear resistance of the weldment was found to increase, due to the formation of carbide. The optical micro-graph of weldment shows the formation of carbide leading to increase in the hardness. No discontinuity and crack were in the weld zone.

The dissolution behavior of carbides in martensitic stainless steel and its effect on microstructure and hardness were investigated by using X-ray diffractometer (XRD) and field emission scanning electron microscopy (FE-SEM) with energy dispersive spectrometer (EDS) and electron backscattering diffraction (EBSD). The results indicated that the microstructure after austenitizing heat treatment and oil quenched consisted of martensite, M23C6 carbides and retained austenite. The temperature and particle size had great influence on the dissolution of carbides. The EBSD results showed that the twin-related variant pair V1/V2 governed the phase transformation. Meanwhile, the density of high-angle grain boundaries (HAGBs) increased with the increase of austenitizing temperature from 950 to 1150 °C. The hardness test results indicated that the hardness first increased and then decreased with the increase of the austenitizing temperature, and the peak appeared at 1050 °C with a Rockwell hardness value of 59.8 HRC. A model was established to quantitatively explain the contribution of different microstructures to hardness. The contribution to hardness came mainly from martensite. The retained austenite had a negative effect on hardness when the volume fraction was more than 10%. In contrast, carbides contributed less to hardness due to their small content.

Microstructure and wear resistance of the hypereutectic Fe–Cr–C alloy hardfacing metals with different La2O3 additives

The effect of vanadium on microstructures and properties of Fe–Cr–C self-shielded metal cored hardfacing alloys was investigated with four hardfacing alloys that contain 0˙73, 2˙3, 3˙1 and 4˙1% vanadium respectively. The effects of vanadium element on microstructures and mechanical properties were analysed. Results indicate that the metal matrix of hardfacing alloys transforms the properties from austenite to austenite and martensite with increasing vanadium content. The metal matrix turns completely into martensite when the vanadium content is up to 4˙1%. Primary carbide is changed from long bulk faceted morphology to spherical and irregular shapes, and a large number of secondary carbides are precipitated and dispersed in the metal matrix of hardfacing alloys with increasing vanadium content. The hardness and wear resistance are also enhanced with increasing vanadium content.

Effect of different carbides on the wear resistance of Fe-based hardfacing alloys