Hardfacing Alloy Research Articles

Effect of heat treatment on the microstructure of additive manufactured Ni-based hardfacing alloy deposits on stainless steel

Ni based (NiCrFeSiBC) hardfacing alloy was deposited on 304 L SS build plate by laser rapid manufacturing (LRM) process. As-deposited specimen showed nearly a precipitate free zone at the interface, grain boundary (GB) precipitation in stainless steel up to 10 µm, thin dilution layer (∼60 µm) followed by formation of zones with distinct microstructure, microhardness and microchemistry in the deposit. To investigate the effect of thermal exposure on the interface microstructure, deposits were heat treated in the temperature range of 823-1123 K for 5-100 h. Up to 923 K, structure of the LRM deposits resembled that of as-deposited specimen. A planar interface region devoid of precipitates was present even after thermal exposure up to 923 K. With further increase in the temperature, formation of CrB precipitates with globular morphology was observed along the deposit/build plate interface with simultaneous increase in hardness. Thermal exposures beyond 923 K promoted coarsening of M7C3 and Cr2B precipitates. Diffusion of carbon and boron from the deposit to the build plate promoted the grain boundary precipitation of chromium carbides up to a maximum distance of ∼1000 µm for the highest temperature of 1123 K.

Fracture Behavior of Hardfacing Alloy Coated Over Stainless Steel under Quasi-Static and Dynamic Loads

AbstractThe fracture behavior of bi-material made of Ni-Cr-B-Si hardfacing alloy deposited over SS316LN substrate was evaluated under quasi-static and dynamic loads. The crack growth started from notch made on the deposit side and progress toward the substrate deposit interface under both loading conditions was monitored. The displacement rate in quasi-static loading and the loading rate for dynamic loading varied and crack propagation was studied. It was observed that the crack was deflected at the interface and not penetrated to the substrate, irrespective of loading conditions. The reason for crack deflection at the interface was analyzed using the energy-based method. It is shown that the ratio of fracture toughness of the interface to that of the substrate (0.044) is lower than the ratio of energy release rate for the deflecting crack to that of the penetrating crack (0.235). Thus, this material combination satisfies the condition for crack deflection rather than penetration. The fracture toughness of the interface was estimated as ~ 68 MPa m1/2 and it falls between that of hardfacing alloy and SS316LN base metal. Optical and SEM examinations were conducted to corroborate the crack path deviations during crack growth. Results suggest that isolated cracks might be present on hardfaced coatings on critical components for which such cracks are usually not permitted. It may be allowed in preference to repair of these cracks, which is difficult and significantly increases the risk of additional cracks forming on the deposits because of the high susceptibility of the hardfacing alloy to cracking.

Mechanisms of elevated temperature galling in hardfacings

The galling mechanism of Tristelle 5183, an Fe-based hardfacing alloy, was investigated at elevated temperature. The test was performed using a bespoke galling rig. Adhesive transfer and galling were found to occur, as a result of shear at the adhesion boundary and the activation of an internal shear plane within one of the tribosurfaces. During deformation, carbides were observed to have fractured, as a result of the shear train they were exposed to and their lack of ductility. In the case of niobium carbides, their fracture resulted in the formation of voids, which were found to coalesce and led to cracking and adhesive transfer. A tribologically affected zone (TAZ) was found to form, which contained nanocrystalline austenite, as a result of the shear exerted within 30μm of the adhesion boundaries. The galling of Tristelle 5183 initiated from the formation of an adhesive boundary, followed by sub-surface shear in only one tribosurface, Following further sub-surface shear, an internal shear plane is activated. internal shear and shear at the adhesion boundary continues until fracture occur, resulting in adhesive transfer.

Revealing the microstructural evolution and mechanical response of repaired Fe–Cr–Si based alloy by directed energy deposition

This study investigates the microstructure and mechanical properties of wear-resistant hardfacing structures fabricated on an AISI 1045 carbon steel substrate using a specially designed Fe–Cr based powder for directed energy deposition (DED). Electron backscatter diffraction (EBSD) analysis reveals that the texture predominantly consists of cube rotated {001}<110> and cube {001}<110> textures, in addition to weaker Brass {112}<111> texture components. These textures contribute to the random orientations of martensitic grains and facilitate the tracing of austenite reconstruction. Notably, the as-printed samples exhibited superior yield strength (999.4 ± 86.3 MPa) and ductility (9.6 ± 2.6%) along the build direction (BD), compared to conventional samples, which demonstrated a tensile strength of 790 MPa and ductility of 2%. This improvement is primarily attributed to the hardening effects associated with a low volume fraction of retained austenite and the precipitation of Cr carbides. Comprehensive mechanical response, nanoindentation hardness profile across the interface, and microstructural analyses were conducted to confirm the feasibility of using a Fe-based hardfacing alloy for DED. The findings underscore the outstanding balance of strength and ductility exhibited by as-printed hardfacing alloy, further enhanced by its high printability, highlighting its potential in producing wear-resistant structures for repair applications.

Effect of powder composition, PTAW parameters on dilution, microstructure and hardness of Ni–Cr–Si–B alloy deposition: Experimental investigation and prediction using machine learning technique

The implementation of hard-facing alloy on the existing materials caters the need for high-performance surfaces in terms of wear and high temperatures. The present research explore the effect of Plasma Transferred Arc Welding (PTAW) parameters and powder composition on dilution, microstructure and hardness of the commonly used hard-facing alloy Ni–Cr–Si–B powder. The hard-facing alloy was deposited with three weight proportions of boron (2.5 %, 3 % and 3.5 %). The statistical-based Grey Relational Analysis (GRA) followed by a Machine Learning Algorithm (MLA) was implemented to identify the ideal parameters and degree of significance of each parameter and for the prediction of the responses. The dilution percentage, microstructure analysis, and phase detection were estimated through elemental analysis, Scanning electron Microscopy (SEM) and X-ray Diffraction Analysis (XRD) respectively. The experimental and modelling results revealed that 400 mm/min of scanning speed, 8 gm/min of powder delivery, 14 mm of stand-off distance, and 120 A of current were the optimal parameters along with 3.5 wt% of boron powder composition to yield a better dilution, microstructure and hardness.

Influence of pressure and powder characteristics on the properties and microstructure of Colmonoy-5 alloy sintered by spark plasma sintering

This study investigates the microstructure and final properties of Colmonoy-5, a nickel-based hardfacing alloy, consolidated via spark plasma sintering (SPS) as an alternative to traditional welding deposition on stainless steel substrates. Two batches of Colmonoy-5 alloy powders with different particle sizes used for sample processing. Sintering occurred at 900 °C under pressures of either 50 MPa or 60 MPa for 15 min. The evaluation of the sintered samples included density measurement through Archimedes' method, morphology assessment via confocal microscopy, phase composition analysis by X-ray diffraction (XRD), microstructural examination using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and hardness testing by Vickers method. Findings indicate that SPS is an effective technique for producing Colmonoy-5, achieving satisfactory densification. The study also reveals that the initial morphology of the precursor powders can influence the size of phases precipitated within the nickel matrix. Sintering pressure of 50 MPa seems to be the most effective in processing Colmonoy-5 via SPS.

Restoration of the Impact Crusher Rotor Using FCAW with High-Manganese Steel Reinforced by Complex Carbides

Abstract A new hardfacing alloy within the Fe-Ti-Nb-Mo-V-C alloying system was utilized to restore the working surfaces of cone crusher rotors using Flux-Cored Arc Welding (FCAW). TiC, NbC, Mo2C, VC, Mn, and ferromanganese powders were selected as the base materials for manufacturing the welding wire. The resulting hardfaced layer exhibits a composite structure, with manganese austenite as the matrix and complex solid solution reinforcements with a NaCl structure, closely resembling the formula (Ti0.3Nb0.3Mo0.3)C. The primary advantages of this hardfacing alloy include its capacity for intensive deformation hardening along with high abrasion resistance. The hardness of the hardfaced layer is approximately 47 HRC in the as-deposited state and increases to around 57 HRC after work hardening, surpassing typical hardfacing alloys derived from high manganese steel by about 10 HRC. The efficacy of the alloy was tested in restoring rotors made of Hadfield steel in a PULVOMATIC series crusher model 1145, during the milling of sand-gravel mixtures ranging from 25 to 150 mm into spalls measuring 5 to 20 mm. With an average productivity of approximately 60 tons per hour and a production volume of 300 tons, the utilization of this hardfacing alloy enabled multiple restorations of the rotor while maintaining productivity at a level of 15 thousand tons of spalls.

Erosion behavior of various high chromium cast iron alloys exposed to gas-blast stream of ferric oxide particles

Depositing hardfacing material onto a surface with the welding method is a common way of protecting surfaces against wear damage. In this study, five high chromium hardfacing alloys were used to prepare samples for the gas blasting erosion test. Erodent particles were ferric oxide specks with a hardness of 657 HV and an average size of 260 μm. Impinging stream eroded the surface of samples with the gas flow of 100 m/s at an angle of 30° while the particle feed was increased from 140 to 630 g. The results indicated that erosion resistance is dominated by bulk hardness of hardfaced alloys. In addition, the erosion rate for a sample containing Mo, Nb, V, and W was the lowest since it had the highest bulk hardness among all other samples.

Effect of alloy 625 buffer layer on corrosion resistance of nickel base hardfacing

Nickel base hardfacing alloys serve to mitigate corrosion losses at elevated temperatures. Efficacy of Nickel base hardfacing alloys can be compromised when applied onto Fe base substrates due to iron dilution in hardfacing. The degree of Fe dilution can be reduced by using advanced deposition methods and optimized deposition parameters. Gas Tungsten Arc Welding (GTAW) method is commonly employed for its cost-effectiveness and versatility, but it tends to induce higher Fe dilution due to increased heat input. This study aims to reduce the degree of Fe dilution and enhance corrosion resistance by introducing a nickel base buffer layer (alloy 625) between the nickel base hardfacing alloy and AISI 316L stainless steel substrate. For comparative purposes, Ni base hardfacing alloy was deposited on the substrate without any buffer layer. Hardfacing depositions were prepared using manual GTAW process. Process parameters namely, deposition current, voltage, travelling speed, pre-heating temperature, and cooling method were kept constant. Samples underwent aging at 1123 K for 4 h, followed by microstructural examination via optical and scanning electron microscopes. Iron (Fe) dilution quantification was performed using energy dispersive spectroscopy (EDS). The EDS analysis showed that the use of buffer layer between the hardfaced deposit and the substrate decreased the degree of Fe dilution in the hardfaced deposit. X-Ray diffraction (XRD) analysis was performed to identify various phases formed in the hardfaced deposit. Potentiodynamic polarization test was performed to assess the corrosion resistance of hardfaced deposit in 3.5 wt% NaCl solution. Results show significant improvement in corrosion resistance of hardfacings deposited sample with buffer layer as compared to those without buffer layer. Aging treatment further enhanced corrosion resistance. The corrosion resistance data is correlated with the microstructure and phases formed in various samples.

Development of novel carbon-free cobalt-free iron-based hardfacing alloys with a hard π-ferrosilicide phase

Recently, iron-based alloys with a π-ferrosilicide phase have emerged as potential alternatives to cobalt-based hardfacing alloys. Here, we present the development of two π-ferrosilicide containing alloys: one with a ferritic matrix and the other with a ferritic-austenitic matrix. In the as-cast condition, both alloys revealed fine Ni- and Si-rich coherent cubic shaped D03 precipitates in the BCC matrix. The π-ferrosilicide phase was found to have an orientation relationship with the ferrite phase, nucleating within ferrite matrix and from ferrite grain boundaries. In contrast to carbide-strengthened hardfacing Fe-alloys, here the dissolution of the π-ferrosilicide phase at 1200 °C enables easy thermomechanical processing of these alloys, which results in refinement of the π-ferrosilicide and additional formation of χ-phase precipitates in the ferrite. Nano-scratch tests provided evidence of a resilient silicide-ferrite interface, likely to due to it possessing some coherency. Both alloys also displayed compressive strengths approaching 2 GPa and ductility in compression of approximately 25 %. The combination of processability and attractive mechanical properties suggests that these alloys have the potential to serve as alternatives to carbide-reinforced hardfacing Fe-alloys.

Crack-free hard facing options for orifice plate used in oil refinery applications

The purpose of this study is to select a suitable tubular wire electrode as an alternative hardfacing material for Stellite 1 in the production of SS304 orifice plates used in oil refineries. It is also intended to develop an efficient deposition procedure for crack-free hardfacing. Compatible cobalt, nickel, and iron-based hardfacing alloys were selected so as to match the hardness and hot hardness properties of stellite 1. Moving heat source analysis was performed to find the heat affected zones and the thermal stress distribution during hardfacing. The significance of weld speed, bead width, and weld concentration on the weld deposition process was analysed using ANSYS, to extract an efficient deposition procedure. The hardfacing alloys were tested for stress and deformation at working temperature (up to 815 οC) to understand the performance. Seven materials were taken into consideration as options along with six parameters. The results revealed a higher longitudinal residual stress of 2000 MPa for Talonite and Tribaloy hardfacing alloys. Colmonoy 6 was found to be having the least stress value of 2186 MPa. Furthermore, the von mises stress values arrived for different conditions showed that the optimal welding condition is 5 mm/s welding speed, 3 mm radius of beam and 455 °C preheat temperature. Microstructural study revealed the dendrite growth in the surface of Colomony 6 hardfacing during solidification, which led to the improvement in mechanical properties.

Effect of manganese and vanadium additions on the microstructures and two-body abrasive wear behaviors of Fe–B hardfacing alloys

Fe–B wear-resistant alloys often exhibit brittleness and suboptimal wear resistance, making them unsuitable for severe operational conditions. In this study, we incorporated ferromanganese powder and ferrovanadium powder were compounded into the Fe–B wear-resistant alloy by plasma cladding technology. The results indicate that the addition of a minor percentage of vanadium, such as about 2 wt%, does not induce any changes in the phase composition. The alloy layer primarily consists of (Mn,Fe)2B and γ-Fe, with vanadium predominantly dissolving in the primary (Mn,Fe)2B phase. This dissolution enhances the toughness of the hard phase and refines the grain structure. At around 4 wt% vanadium, a spherical VB phase precipitates. This inclusion elevates the impact toughness of the alloy layer. The impact toughness of the high manganese content with 4.69 wt% vanadium is the highest, up to 39.11 J/cm2, which is about 30 %higher than that of the sample without vanadium. As vanadium content rises, both the hardness and wear resistance of the alloy layer improve. The most optimal performance was observed with a manganese content of 20.15 wt% and vanadium at 4.69 wt%, achieving a hardness of 65.5 HRC and wear amounts of 48.1 mg (24 N load) and 85.0 mg (48 N load).

Prediction of phase composition and mechanical properties Fe–Cr–C–B–Ti–Cu hardfacing alloys: Modeling and experimental Validations

Alloys of the Fe–Cr–C–B–Ti alloy system are characterized by brittleness, which can be eliminated by the copper alloy, while corrosion resistance and abrasive wear resistance are significantly reduced. In this article, comprehensive investigations are carried out on the microstructure and mechanical properties of the proposed high-copper boron-containing alloy 110Cr4Cu7Ti1VB. Systematic theoretical and experimental studies encompassed thermodynamic calculations in ThermoCALC, production of flux-cored wires for hardfacing and welding, receipt of SEM images, acquisition of load and unload diagrams (discharge) via instrumental indentation on various phases of the deposited metal, and determination of chemical composition at indentation points through local chemical analysis. Mechanical properties of some phases such as γ–Fe phase (austenite), hemioboride Fe2(В,С) and boron cementite Fe3(В,С) and titanium carbide TiC in Fe–Cr–C–B–Ti–Сг alloy were determined by using density functional theory (DFT) implemented in the CASTEP code. We also compared these compounds; properties with other available commercial compounds, where available. With the knowledge of calculated elastic constants, the moduli, the Pugh's modulus ratio G/B, the Poisson's ratio v and the hardness of the title phases, 110Cr4Cu7Ti1VB were further predicted and discussed.

Enhanced mechanical properties of Fe-based hardfacing alloy with Al additions fabricated by laser cladding

Laser cladding was used to prepare an Al-containing Fe-Cr-C hardfacing alloy layer on a 316 L stainless steel substrate. The effects of Al addition on the elemental distribution, physical phase composition, and properties of the cladding layers were systematically investigated using experimental observations, finite-element simulation, and performance tests. Aluminum promoted the flow and elemental homogenization of the molten pool, leading to a more dispersed carbide distribution. Aluminum increased the thermal conductivity of the material and accelerated the cooling rate of the melt pool, which suppressed the eutectic reaction L → γ + (Fe,Cr)7C3 and promoted the peritectic reaction L + (Fe,Cr)7C3 → γ + (Fe,Cr)3C. Consequently, the (Fe,Cr)7C3 content decreased, whereas that of (Fe,Cr)3C increased. Aluminum improved the stability of ferrite and promoted its formation. The Al addition resulted in fine-grain, load-transfer, dislocation, and Orowan strengthening, thereby improving the hardness and wear resistance of the Fe-Cr-C hardfacing alloys. Dislocation and Orowan strengthening were the largest contributors, followed by fine-grain and load transfer strengthening.

Residual Stress Map for 75Ni13.5Cr2.7B-3.5Si Clad 316 Stainless Steel

Plasma Transfer Arc (PTA) process uses the intense heat of electric arc to melt and fuse the 75Ni13.5Cr2.7B-3.5Si hard-facing alloy and the base metal. This process develops substantial residual stresses near the hard-faced surfaces during deposition and subsequent solidification and cool down. Furthermore, when a material interface is present, additional residual stress is formed because of the thermal strain mismatch of the dissimilar materials caused by their different thermal expansion coefficients. These stresses can cause cracks in the overlay during the component’s service life or even earlier during manufacturing which can lead to partial or total loss of the part structural integrity. To start optimizing the process to avoid these defects, it is necessary to know the residual stress distribution in the part and how it is related to the process parameters. Hard-faced components are having distinct microstructures with a step change in material properties, and this makes the residual stress measurement more challenging. This paper presents 2D residual stress maps of the deposit cross sections for PTA hard-faced samples using the contour method. This study is part of an ongoing research on the influence of process parameters on the residual stress and local microstructure of 75Ni13.5Cr2.7B-3.5Si clad 316 stainless steel.

Microstructure and wear resistance of in situ TiC-reinforced low-chromium iron-based hardfacing alloys

Microstructure and wear resistance of in situ TiC-reinforced low-chromium iron-based hardfacing alloys

Thermodynamic Analysis of the Corrosion Behaviour of Hardfacing Alloys Containing Chromium Nitrides

Chromium nitrides such as CrN and Cr2N are often used for corrosion and wear resistant applications. In order to understand the thermodynamic stability of the nitrides, Pourbaix diagrams will be extremely useful. In this paper, Pourbaix diagrams are constructed for CrN and Cr2N using thermodynamical data for species at 298 K (25 °C) and at a concentration of 10−6 M for aqueous species. These diagrams are useful indicators for the stable regions in which these compounds can be used. The diagrams show that passive Cr2O3 films form on the surfaces where chromium nitride was present. It is argued that the formation of Cr2O3 films will degrade chromium nitride and make it much less useful as a wear resistant layer. However, the presence of nitrogen in solid solution is better for the stability of passive films.

Phase Selection and Microstructure Evolution in Laser Additive Manufactured Ni-Based Hardfacing Alloy Bush

Phase Selection and Microstructure Evolution in Laser Additive Manufactured Ni-Based Hardfacing Alloy Bush

Material Health of NiCrBSi Alloy Parts Produced via the Laser Powder Bed Fusion Process

Laser powder bed fusion (L-PBF) is a novel process representing a possible solution for producing resistant parts using NiCrBSi hard-facing nickel alloys with complex geometry. Process parameters for more common alloys are explored with a standard Renishaw AM400 device (Renishaw, Wotton-under-Edge, UK) and an SLM Solution 250 device (SLM Solutions Group AG, Lübeck, Germany) modified with a baseplate preheated at high temperatures (300 °C and 500 °C). Laser remelting is also investigated in hopes of further improving material health. The origin of the main defects is studied. A lack of fusion is likely to be generated by spatters ejected from the melting pool while cracks are induced by the alloy’s lack of toughness. Using image analyses, those defects are quantified and correlated with processing parameters. Lack of fusion and total crack length decrease with an increase in baseplate’s preheating temperature. However, crack width increases with preheating temperature. Therefore, via a careful optimization of process parameters, samples with a surface density of 99% and narrow cracks are obtained.

Microstructure and mechanical properties of ZrC modified Ni60 hard-facing alloy fabricated by laser metal deposition

Crack-free specimens were prepared from ZrC-modified Ni60 alloy by laser metal deposition. The effects of ZrC powder adulteration on the mechanism of microstructure refinement were investigated. The results demonstrated that the adulteration of ZrC powder did not provide nucleation sites for the hardening phase. The ZrC powder was added to Ni60 alloy powder to reduce the content of columnar dendrites and the eutectics of laser metal deposition specimens. The transformation of the dendritic hardening phase into a massive hardening phase was induced. The fine Ni–B–Si eutectic microstructure changed to a massive NiZr eutectic and peritectic microstructure with increasing ZrC powder mass fraction. The microstructure transformation mechanism constrained the initiation and propagation of cracks in the deposited specimens. The present research provides a method for improving the cracking defect of laser additive manufacturing Ni–Cr–B–Si system alloys and a theoretical basis for promoting the application of the alloy in additive manufacturing.