M23C6 Phases Research Articles

Microstructure and wear resistance of multi-layer graphene doped AlCoCrFeNi2.1 high-entropy alloy self-lubricating coating prepared by laser cladding

A novel AlCoCrFeNi2.1 high-entropy alloy self-lubricating coating was prepared by multilayer graphene (MLG) enhancement. The AlCoCrFeNi2.1-MLG (3 wt%) high-entropy alloy self-lubricating coating was prepared on AISI1045 steel using laser cladding by introducing lubricant named MLG. The microstructure, phase structure, wear resistance and corrosion performance of the AlCoCrFeNi2.1-MLG coating were studied. It is shown that the microstructure of the AlCoCrFeNi2.1-MLG coating has typical dendritic (DR) and interdendritic (ID) structures, with the dendrites consisting of high density M23C6 phase precipitation and FCC phase distributed in the interdendritic region. With the addition of MLG, the average hardness of the AlCoCrFeNi2.1 coating increases from 306.71 HV to 486.68 HV (an increase of 58.68 %). The average coefficient of friction decreases from 0.59 to 0.48 (a reduction of 22.92 %). The wear rate decreases from 1.678 × 10- 6 mm3·N− 1 m−1 to 0.825 × 10- 6 mm3·N− 1 m− 1 (a reduction of 50.83 %). This is due to the formation of a lubricant film in the AlCoCrFeNi2.1-MLG coating. The wear mechanism changes from plastic deformation and abrasive debris wear to slight delamination and spalling of the lubricant film. However, the corrosion performance of the AlCoCrFeNi2.1-MLG coating is slightly reduced by the occurrence of micro-electro-coupling corrosion on the corroded surface. The M23C6 phase is used as the anode and the FCC phase is used as the cathode. The subsequent generation of a passivation film prevents the appearance of severe electro-coupling corrosion. The wear resistance of the AlCoCrFeNi2.1-MLG coating is substantially improved while taking into account the corrosion performance. This study provides important values for laser cladding of self-lubricating composite coatings of high-entropy alloys.

Study on the Effect of Co Microalloying on the High‐Temperature Tensile Behavior of 4Cr5Mo2V Hot Work Die Steel

The hot work die steel 4Cr5Mo2V has insufficient high‐temperature strength, making it difficult to meet advanced manufacturing requirements. Herein, a novel modified 4Cr5Mo2V‐Co steel with 0.5% Co addition is designed and subjected to tensile tests at room and high temperature, and the precipitation formation and microstructure evolution are characterized by optical microscopy, scanning electron microscopy, electron backscatter diffraction, X‐ray diffractometer, and high‐resolution transmission electron microscopy. The results show that Co microalloying increases the strength of 4Cr5Mo2V steel while slightly decreasing its plasticity with temperatures ranging from 25 to 700 °C. The increased high‐temperature strength of 4Cr5Mo2V‐Co steel is mainly attributed to dislocation and precipitation strengthening. This can be attributed to the addition of Co lowering the stacking fault energy of bcc grains, preventing dislocation climb and cross slip, thus increasing the dislocation density. In turn, the dislocations provide more nucleation sites for M2C phase precipitation, promoting more dispersed nanoscale M2C phase formation. During high‐temperature tensile deformation, the recrystallization softening phenomenon of 4Cr5Mo2V steel is more pronounced due to the presence of continuous dynamic recrystallization.

Microstructure and tribological performances of laser cladded FeCoCrMoSi amorphous coating under different normal loads

PurposeThe aim was to investigate the effect of normal load on the tribological performance of laser cladded FeCoCrMoSi amorphous coating, which might choose the appropriate normal load for the friction reduction and wear resistance.Design/methodology/approachA FeCoCrMoSi amorphous coating was prepared on 45 steel using laser cladding, and the tribological performance of obtained coating under the different normal loads was investigated using a ball-on-disk tribometer.FindingsThe FeCoCrMoSi amorphous coating is composed of M23C6, Co6Mo6C2 and amorphous phases, where the M23C6 hard phase enhances the coating hardness to increase the wear resistance and the Co6Mo6C2 with the vein shape forms the strong mechanical interlock to play the role of friction reduction. The average coefficients of friction of containing amorphous FeCoCrMoSi coating under the normal loads of 3, 4 and 5 N are 0.68, 0.65 and 0.53, respectively, and the corresponding wear rates are 17.7, 23.9 and 21.9 µm3•N−1•mm−1, respectively, showing that the appropriate normal load is beneficial for improving its friction reduction and wear resistance. The wear mechanism is composed of adhesive wear, abrasive wear and oxidative wear, which is attributed to the high hardness of amorphous coating by the amorphous phase.Originality/valueThe FeCoCrMoSi amorphous coating was first applied for the improvement of 45 steel, and the effect of normal load on its tribological performance was investigated.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2024-0304/

Research on Ni-WC Coating and a Carbide Solidification Simulation Mechanism of PTAW on the Descaling Roll Surface

The descaling roll is a critical component in a hot-rolling production line. The operating conditions are significantly impacted by water with high-pressure and dynamic shocks caused by high-temperature steel slab descaling. Roll surfaces often experience wear and corrosion failures. This is attributed to a combination of high temperatures, intense wear, and repeated thermal, mechanical, and fluid stresses. Production costs and efficiency are significantly affected by the replacement of descaling rolls. Practice shows that the use of plasma cladding technology forms high-performance coatings. Conventional metal surface properties can be significantly improved. In this study, a Ni-WC composite coating was prepared on the descaling roll surface by plasma-transferred arc welding (PTAW) technology. The microstructure and phase composition of the welding overlay were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results show that the WC hard phase added to the molten pool dissolves, and subsequently M7C3 and W2C phases are formed. To further explore the morphological evolution mechanism of the hard phase, numerical simulations were performed using a phase-field method to model M7C3 phase precipitation. The evolution from nucleation, rod-like growth, to eutectic structure formation was revealed. Experimental and simulation results show high consistency, validating the established phase-field model. In this study, a theoretical foundation for designing and preparing high-performance coatings is provided.

Enhanced wear resistance and fracture resistance of spherical WC reinforced nickel-based alloy coating by adding non-spherical WC

Spherical WC particles are widely employed as hard phases to reinforce metal matrix coatings; however, their deposition during the surfacing process presents a significant challenge, resulting in limited improvements in coating hardness and wear resistance. In this work, these spherical WC as well as spherical/non-spherical WC particles have been used to prepare the WC reinforced nickel-based alloy coatings. The microstructure, mechanical, wear and fracture behavior of these coatings were investigated by detailed characterization. Results showed that spherical WC exhibited rapid sedimentation, and the primary decomposition products existed lump-like W2C. The ultimate decomposition process was based on the exfoliation of the diffusion layer. The spherical WC/Ni coatings exhibited a hardness of 13 GPa and an elastic modulus of 253 GPa, respectively. Notably, the wear rate of these coatings was relatively high, measuring 7.038 × 10−6 mm3/(N·m), while the stress and strain were comparatively low, standing at only 272.5 MPa and 0.72 %. In contrast, spherical/non-spherical WC/Ni coatings demonstrated distinct differential sedimentation behavior. Spherical WC particles settled at the bottom of the coating, whereas non-spherical WC particles were dispersed in the middle and upper regions. The decomposition of non-spherical WC particles was governed by the dissolution and diffusion of W2C, forming a skeleton-braided structure of M7C3, γ, and M23C6 phases on the coating surface. This unique structure increased the hardness of the coating to 21 GPa and the elastic modulus to 369 GPa, while reducing the wear rate to 2.853 × 10−6 mm3 (N · m) −1. In addition, the stress and strain reached 497.10 MPa and 1.97 % respectively, shifting the fracture mode to quasi-cleavage fracture with tear ridges. Overall, the spherical/non-spherical WC/Ni coating exhibited improved deformation resistance and superior wear resistance.

The effect of the menstrual cycle phases on back squat performance, jumping ability and psychological state in women according to their level of performance -a randomized three-arm crossover study

ObjectiveThe influence of the menstrual cycle on practical power performance such as barbell back squats and jumping performance in women has not yet been fully investigated. In addition, the performance level of athletes has not been considered in previous studies. This study aimed to investigate the influence of different cycle phases on acute back squat performance, jumping ability and psychological state concerning the performance level.Methods24 female strength athletes (age: 25.2 ± 3.3 years; height: 169.5 ± 3.4 cm; body weight: 67.7 ± 7.3 kg) were recruited for the study. Level of performance was classified according to Santos et al. (intermittent (n = 13), advanced (n = 6), highly advanced (n = 5)). Participants were tested for 1RM barbell back squat and jumping performance (countermovement and squat jump) as well as two questionnaires assessing their psychological states in the menses (M), late follicular phase (FP) and mid-luteal phase (LP) in three MC. Saliva estradiol and progesterone concentrations with a menstrual cycle diary were used to confirm a normal MC. A principal components analysis for power performance, well-being, relaxation and alertness was carried out and a linear mixed model was used for statistical evaluation.ResultsNo significant differences were found between the MC phases in performance scores (p > 0.05), readiness (p > 0.05) and alertness (p > 0.05). However, a high correlation between MC phases, performance level and back squat performance was detected. Correlation analyses indicate that a higher performance level results in a higher variation depending on the MC of the squat performance. For well-being, a significantly lower score was detected in M than in FP and LP.ConclusionIn general the performance score of the lower body is not influenced by the MC. If strength performance and jumping ability are considered separately, there are indications that strength capability is influenced at a higher performance level. In addition, individual variance was also observed, so this should also be considered. However, further studies are needed to confirm this assumption due to the small sample sizes of the individual performance levels.Trial registrationGerman registry for clinical studies (DRKS00034816, Date: 08/01/2024).

Research on the multi environmental corrosion characteristics and mechanism of B4C doped Fe–Cr–Ni composite coating produced by laser cladding

Different Fe–Cr–Ni composite coatings doped with B4C were produced on the surface of Cr12MoV steel by laser cladding. Special attention was paid to the effects of B4C content on the phase composition, microstructure, and corrosion resistance of the cladded layers. The results indicated that the Fe–Cr–Ni composite coating was primarily composed of α-(Fe, Cr) and γ-(Ni–Cr–Fe) solid-solution phases, as well as Fe2B, M7C3, Fe3Si and M23C6 phases. Once the B4C content increased to 10 wt%, the microstructure of the cladding layer became coarse and exhibited the prominent carbide agglomeration. The composite coatings with different B4C contents exhibited superior corrosion resistance compared to the pure substrate in both 3.5 wt% NaCl and 1 mol/L HCl solutions. Furthermore, as the B4C content increased, the corrosion resistance of the coating initially increased and then declined. In particular, the Fe–Cr–Ni composite coating with an 8 wt% B4C content experienced the pronounced passivation in the corrosive media and possessed the optimal corrosion resistance due to the synergistic effect of the passive film and carbide barrier layer.

Influence of ultrasonic assistance on the microstructure and friction properties of laser cladded Ni60/WC composite coatings

The effects of different ultrasonic vibration powers on the distribution, phase structure, friction and wear properties of WC reinforced particles in laser melted Ni60/WC composite coatings are investigated. The effects of ultrasonic vibration on the microstructure, elemental distribution, crystal orientation, friction and wear properties of the fused coatings are analyzed. The experimental results show that the deposition of WC particles in the lower and middle parts of the coating is significantly improved after the introduction of ultrasonic vibration during the fusion cladding process. In particular, at 600 W ultrasonic power, not only the distribution uniformity of tungsten carbide particles in the coating is optimal, but also the composite coating shows better wear resistance. However, too much ultrasonic power increases the possibility of particle agglomeration. In addition, although the phase pattern of the coating does not change after ultrasonic vibration, the width of the columnar crystalline region of the coating is reduced, and the coating is covered by a homogeneous lamellar nanoscale eutectic structure with the phase compositions of the γ-(Fe, Ni) and M23C6 phases. The ultrasonic vibration improves elemental segregation of the coating, reduces the large number of precipitated phases in the coating, weakens the grain growth orientation, and relieves the local stress concentration in the coating. In addition, the mechanism of the influence of WC particles on the microstructure evolution and wear resistance of the composite coatings is discussed.

Tracking research on the performance changes of S31042 steel under long term service

S31042 is widely used in ultra-supercritical units due to its excellent comprehensive performance at high temperatures. Tracking and monitoring research was conducted on as-received S31042 tubes and tubes in service for 13 k hours, 31 k hours, and 52 k hours at 650 °C. The results show that as the service time increased, a large quantity of M23C6 phase precipitated along the grain boundaries, gathered and grew up into the bulk. This weakened of the grain boundaries, which facilitated crack propagation and significantly reduced the plasticity and toughness of the S31042 heat-resistant steel. After 13 k hours of operation, the dispersion strengthening of the precipitated phase inside the grain and grain boundary led to a substantial increase in hardness, while there was no obvious change in strength. However, after 52 k hours of operation, the dispersed precipitated phase within the grain slowly aggregated and grew, decreasing the effectiveness of dispersion strengthening. Consequently, both the high-temperature strength and hardness of the S31042 steel gradually decreased. As the service time increased, the continuously distributed and similarly sized M23C6 phases on the grain boundaries of S31042 developed into an inhomogeneous coarsening chain structure. Additionally, the appearance of nanoscale secondary NbCrN and M23C6 phases within the grain and their resulting precipitation strengthening effects were the main reasons for the significant change in S31042 hardness values. Based on these findings, the residual life of S31042 heat-resistant steel in service was predicted using an extrapolation method based on high-temperature creep rupture tests and the relationship model between hardness and the P function. A comparison of the L-M parametric life prediction results with the strength extrapolation life prediction results based on the standard creep rupture test shows that the creep rupture strength extrapolation method is slightly conservative. Therefore, the prediction results based on the hardness L-M parameter method, which is simple and easy to perform, can be used for preliminary life prediction.

Influence of menstrual cycle and oral contraceptive phases on strength performance, neuromuscular fatigue, and perceived exertion.

The primary aim of the study was to assess differences in strength performance, neuromuscular fatigue, and perceived exertion across phases of the menstrual cycle [MC; early follicular (eFP), late follicular (lFP), and mid-luteal phase (mLP)] and oral contraceptives [OCs; active pill phase (aPP) and nonactive pill phase (nPP)]. The secondary aim was to analyze the influence of fluctuating serum 17β-estradiol and progesterone concentrations on these parameters in naturally menstruating women. Thirty-four women (21 with a natural MC and 13 using OCs) completed three or two experimental sessions, respectively. Mean propulsive velocity (MPVmean) and total number of repetitions (REPtotal) were assessed during a power [3 × 8 at 60% 1RM (one-repetition maximum)] and hypertrophy squat loading (3 sets to failure at 70% 1RM), respectively. Changes in bench press and squat MPV at 60% 1RM in response to the loadings were used as surrogates for nonlocal and local fatigue, respectively. Total blood lactate accumulation (BLAA) and markers of perceived exertion were assessed in each session. No significant differences between any of the MC or OC phases were observed for MPVmean, REPtotal, nonlocal and local fatigue, and markers of perceived exertion (all P > 0.050). A higher intraindividual 17β-estradiol concentration was significantly associated with a lower MPVmean (P = 0.019). BLAA was significantly higher in the lFP than in the mLP (P = 0.019) and negatively associated with the intraindividual progesterone concentration (P = 0.005). Although 17β-estradiol may negatively influence the MPV, it appears that fluctuations of both sex hormones across the MC and OC phases are not prominent enough to induce significant or practically relevant changes in the assessed parameters.NEW & NOTEWORTHY Although a high intraindividual 17β-estradiol concentration was associated with a lower movement velocity, markers of strength performance and surrogates for nonlocal and local fatigue remained unaffected by MC and OC phases. Blood lactate accumulation was significantly reduced in the mLP. Furthermore, our findings suggest that the impact of the MC phases varies greatly among individuals. Individuals with high fluctuations in sex hormone concentrations may experience relevant changes in the assessed parameters.

Long-term thermal aging effects in ferritic-martensitic steel HT9

The ferritic-martensitic steel HT9 is a candidate material for fuel cladding and core components in advanced nuclear reactors, such as sodium-cooled fast reactors, thanks to their high temperature mechanical properties and low susceptibility to irradiation induced swelling phenomena. However, thermal stability and elevated temperature microstructural evolution in these alloys may impact their long-term behavior and reliability. In this work, the effects of thermal aging on the microstructural and mechanical properties of HT9 have been investigated through complementary electron microscopy, synchrotron X-ray diffraction, microhardness, and thermodynamic modeling. Plates of HT9 were aged up to 50 kh at relevant sodium-cooled fast reactor operational temperatures (360 °C - 700 °C). Trends in microstructure as a function of aging time and temperature were apparent from qualitative and quantitative analysis. These observations were further supported by thermodynamic modeling of the bulk and precipitate phases. Specific phases observed include BCC Fe, FCC M23C6, HCP and FCC MX phase and Laves M2X phase. Through the application of our multi-scale and multi-modal approach, clear information on the aging mechanism of HT9 was obtained, allowing for a more informed prediction, and understanding of the long-term behavior, performance and thermal stability of ferritic-martensitic alloys exposed to elevated temperatures.

Experimental Study on the Microstructure and Tribological Properties of Laser-Clad Ni60-WC Composite Coatings.

To address the wear issues faced by the leg components of offshore platforms in harsh marine conditions, a Ni60-WC composite coating was fabricated on the surface of E690 high-strength steel using laser cladding. The microstructure, elemental distribution, microhardness, and tribological properties of the composite coating were characterized and tested using XRD (X-ray diffraction), SEM (scanning electron microscopy), EDS (energy-dispersive spectrometry), a microhardness tester, and a multifunctional tribometer. The study focused on the microstructure and tribological properties of the Ni60-WC composite coating. The results show that the composite coating primarily consists of γ-(Fe, Ni), WC, W2C, M23C6, and M6C phases, with cellular and dendritic structures at the top. WC and W2C, along with M23C6 and M6C, are precipitated from the W and C elements. The average hardness of the composite coating reached 569.5 HV, representing a 103% increase over the substrate hardness. The prepared composite coating exhibited a 32.6% increase in corrosion potential compared to the substrate. Additionally, the corrosion current density was reduced by 62.0%, indicating a significant enhancement in the corrosion resistance of the composite coating. The friction coefficient of the composite coating was reduced by 17.4% compared to the substrate, and wear volume was reduced by 79%, significantly enhancing the tribological performance of the coating due to reduced abrasive wear and fatigue wear.

Wear performance of CoCrFeMnNi and CoCrFeMnNi-SiC coatings on 0Cr18Ni9Ti stainless steel fabricated by plasma transfer arc cladding

To enhance the wear resistance of stainless steel, CoCrFeMnNi and CoCrFeMnNi-SiC coatings were deposited on 0Cr18Ni9Ti via plasma transfer arc cladding. Effects of SiC particles on microstructure, microhardness and tribological properties of the CoCrFeMnNi coating were investigated. Results demonstrate that, in addition to the FCC solid solution and a small amount of oxide, the CoCrFeMnNi-SiC coating contains M23C6 and M7C3 phases, which exhibit an average hardness approximately 2.3 times that of the CoCrFeMnNi coating. Meanwhile, the wear resistance of the composite coating under different loads was improved, which was attributed to the fact that the high hardness SiC reduced the shear and adhesion between the coating and the mill ball, and the composite coating received abrasive and oxidative wear.

Synergistic optimization of microstructure and mechanical properties of AISI 430 ferritic stainless steel via dual-phase zone annealing process

This study systematically evaluated the impact of dual-phase zone annealing on the microstructure and mechanical properties of cold-rolled 430 Ferritic Stainless Steel (FSS), focusing on the phase transformation process from ferrite to austenite and the dissolution and precipitation behavior of the M23C6 phase. The annealing process significantly affects the microstructural characteristics of ferrite and martensite, including grain size, the distribution of grains of various sizes, aspect ratio, and phase content. The amount of martensite first increased and then decreased with rising annealing temperatures. The sample annealed at 1050 °C exhibited the highest martensite content of 29.5%. The variation in martensite content reflects the complex interplay between phase transformation kinetics and thermodynamic equilibrium. As the annealing time increased or temperature rose, the M23C6 phase at ferrite grain boundaries gradually dissolved and re-precipitated at higher temperatures. At lower temperatures, the M23C6 phase precipitated within martensite, but as the temperature increased, the precipitated phase diminished until it disappeared. Temperature changes affect the solubility of precipitates, atomic diffusion rates, and the uniform distribution of atoms across different phases. Appropriately increasing annealing temperature or extending annealing duration enhances the strength and hardness of 430 FSS. However, excessively high annealing temperatures lead to a decline in mechanical properties. The sample annealed at 1000 °C demonstrated the best mechanical properties, achieving a tensile strength of 783 MPa and an elongation of 16.0%. Furthermore, the analysis of fracture morphology and yield behavior in stress-strain curves further elucidated the macroscopic mechanical performance of the material.

Identification of nano-sized precipitates in CLAM steel induced by 3.5 MeV Fe13+ ion irradiation

Nano-sized precipitate phases in normalized-and-tempered CLAM steel (HEAT-0912) before and after 3.5 MeV Fe13+ ion irradiation at 400 °C to 0.61, 1.29 and 2.77 dpa were studied using transmission electron microscope and high-resolution transmission electron microscope. Six types of nanoprecipitate phases based on Cr23C6, TaC, Ta3C2, VC, Cr7C3, and V2C were identified in unirradiated steel. During irradiation, a large number of nanoprecipitates uniformly distributed in the matrix occurred, and the number density of nanoprecipitates initially increased and subsequently decreased with increasing the irradiation dose. Nanoscale Cr-rich M23C6, V-rich MX and M2X phases but no nanoscale phases based on TaC, Ta3C2 and Cr7C3 were identified in the steel irradiated up to 2.77 dpa. After irradiation, five types of irradiation-induced nanoscale new phases were identified in the irradiated steel. These include Fe-rich M3X2 (Cr3C2 types I and II) carbonitrides with the same simple orthorhombic lattice and totally different lattice parameters (approximately a/b/c = 1.146/0.552/0.2821 nm and 0.285/0.925/0.696 nm), Fe-rich M2C, M3C and M5C2 carbides, but the occurrence of which under irradiation varied with the irradiation dose. Fe-rich M3X2 (Cr3C2 type I) and Fe-rich M5C2 phases were identified in the steel irradiated up to 1.29 dpa and only to 2.77 dpa, respectively. Fe-rich M2C and M3C in addition to Fe-rich M3X2 (Cr3C2 type II) phases were identified in the steel irradiated up to 2.77 dpa. The irradiation-induced Fe-rich M3X2 (Cr3C2 type I & II), M5C2 and M2C precipitates appear to be identified, for the first time, in reduced activation ferritic/martensitic steels including CLAM steel. The formation mechanism of these irradiation-induced precipitate phases is also discussed.

Corrosion behavior of laser directed energy deposited SS316L/Inconel718 functionally graded materials

Functionally graded material (FGM) can exhibit a variety of excellent properties by controlling layer-by-layer gradients in composition and microstructure. In this paper, SS316L/Inconel718 FGM was fabricated by laser directed energy deposition (LDED) to investigate the microstructures and corrosion behaviors at the transitional interfaces. The results indicate that the microstructures in gradient regions along the build direction include cellular crystals, dendritic structures, columnar crystals, and equiaxed crystals. With increasing mass fraction of IN718, the precipitates within the FGM matrix transition from metal oxides to Laves phases and MC phases, accompanied by elemental segregation of Nb and Mo at the grain boundaries. The enhanced corrosion resistance is attributed to the increased pitting corrosion resistance elements within the FGM matrix. Additionally, the high content of Cr2O3 and NiO in the passive film enhance the corrosion resistance. The SKP and LEIS test results indicate that the LDED-manufactured SS316L/IN718 FGM exhibits no apparent galvanic coupling corrosion and maintains excellent corrosion resistance transition. This investigation offers a reference for the study of corrosion-resistant composite materials.

Friction behavior and wear mechanism of laser cladded FeNiCr-WC composite coatings in comparison with different friction pairs

Complex formation structures lead to significant differences in the failure mechanisms of hobs. WC-reinforced medium entropy composite coatings exhibit excellent comprehensive properties. However, the wear mechanism of coatings in different formation structures is still unclear. In this study, FeNiCr-WCx (x = 0, 40, 50, 60 wt%) composite coatings were prepared on the surface of H13 steel using laser cladding technology. The friction and wear mechanism of FeNiCr-WC composite coatings under different friction pair conditions was discussed. The results show that FeNiCr-WC composite coatings mainly consist of reinforced phase, lamellar eutectic structure and solid solution phase. As the WC content increases, the content of M6C and carbide phases in these coatings increases. The average microhardness of 40WC, 50WC and 60WC coatings is 3.28 times, 3.61 times and 4.20 times that of H13 steel, respectively. The wear rates of 40WC, 50WC and 60WC coatings are respectively about 0.25, 0.10 and 0.06 times that of FeNiCr coating under Al2O3 friction pair conditions. Three-body wear and oxidation wear mainly occurred on the surface of FeNiCr-WC composite coatings. The wear rates of 40WC, 50WC and 60WC coatings are respectively about 0.34, 0.35 and 0.16 times that of FeNiCr coating under Si3N4 friction pair conditions. Glaze layers with high Si content were formed on the surface of 50WC and 60WC coatings. The glaze layer is prone to cracking and peeling, resulting in increased wear rates for both coatings. As the hardness of the coating increases, the GCr15 friction pair undergoes severe abrasive wear.

Dissolution behaviour of WC particles and evolution of precipitated phases in the plasma transfer arc Ni-based composite coating reinforced by 30 wt% WC particles

Ni-WC composite coating was prepared on Q235 steel substrate by plasma transfer arc (PTA) with welding current ranging from 70 A to 85 A. The results show that the dissolution behaviour of WC particles and the elemental diffusion at the interface promoted by the increased welding current promote the formation and evolution of precipitates, including M7(B, C)3 and M6C. The increased current reduced the volume fraction of WC particles in the coating, but increased that of the precipitates. At welding currents of 75 A and 80 A, dendritic-like M7(B, C)3 presented a regular distribution at the bottom of the coating. At a welding current of 80 A, M6C phase began to form at the bottom of the coating. When the welding current reached 85 A, the dendritic structure was broken, and the M6C phase aggregated and grew. The Ni-WC coating had visible delamination. WC particles at the upper part of the coating dissolved more severely compared to those at the middle and bottom of the coating. Ni3Si compound was formed at the upper and middle of the coating, and it had a crystal orientation relationship of [011]Ni3Si∥[011]γ-Ni, (11-1)Ni3Si∥(11-1)γ-Ni, (−200)Ni3Si∥(-200)γ-Ni, (-11-1)Ni3Si 1.3° from (-11-1)γ-Ni with γ-Ni. The average hardness of the coating decreased slightly due to the dissolution of WC, but the hardness at the interface increased, showing an improved bonding of the interface. The newly formed high hardness precipitates can share the load coming from the friction paired ball, thus reducing CoF and wear loss of the coating.

Investigation of high-temperature wear behavior of Ni-Mo alloyed hardfacing coatings applied on hot strip mill vertical rolls by submerged arc welding

In this study, hot strip mill vertical rolls made of AISI 4140 steel, commonly used in the iron and steel industry's hot rolling section, were coated with ER430 and E430+EC410NiMo using the submerged arc welding (SAW) method. The coatings were characterized through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), microhardness, and wear testing (room 24 °C, 300 °C, and 600 °C). XRD analysis showed that in the ER430 sample, the dominant phase was α-ferrite phase and a small amount of γ (austenite) phase observed, while in the ER 430+EC410NiMo sample, the α-ferrite phase was the dominant phase, but the γ (austenite) phase in the structure was more severe and additionally M6C carbide phase was formed. Coating thicknesses and microhardness values of ER430 and ER430+EC410NiMo coatings were measured as 1.5 mm and 3.75 mm thicknesses, and 533±42 HV0.1 and 473±35 HV0.1 respectively. The increase in hardness on the surface of coated specimens resulted in higher wear resistance compared to the uncoated specimens under all conditions. Regarding average friction coefficient values, coated specimens generally exhibited lower values, although in some cases, the average friction coefficient was higher. In the wear tests, the lowest wear volume losses occurred in the tests conducted at 300°C, while the highest wear volume losses were observed in the tests at 600°C. Upon evaluating the wear mechanisms, it was determined that adhesive and oxidative wear mechanisms were generally dominant in the coated specimens. At higher temperatures, oxidative wear mechanisms became more prominent. ER430+EC410NiMo coatings exhibited better wear resistance compared to ER430, which can be attributed to the toughness effect of γ (austenite) and M6C phases in these coatings. Consequently, it was concluded that applying powder deposition coatings onto hot strip mill vertical rolls made of AISI 4140 steel could enhance their wear resistance, thereby increasing productivity in manufacturing processes.

Synergistic toughening by a layered microstructure and texture of Si-enriched ferritic/martensitic(F/M) heat resistant steel

In order to achieve favorable heat corrosion resistance, it is effective to add high Si contents to F/M heat resistant steel. Unfortunately, the high Si content results in a significant deterioration of impact toughness. Determining how to balance heat corrosion resistance and impact toughness has been a challenge. In this paper, we optimize austenite isothermal hot-rolling (AIHR) technique to the 10Cr1SiY F/M dual-phase heat resistant steel with 1% Si(wt.), to obtain layered microstructure with thread-like δ-ferrite. This decreases ductile-brittle transition temperature (DBTT) from 149 °C to 15 °C, and increases impact energy from 8 J to 107 J, compared to the quenched and tempered steel with the same chemical composition. According to the instrumented Charpy impact tests, higher impact energy derives from the absorbing energy during crack propagation, accounting for 94.9% of the total absorbing energy. The weak interfaces in the layered microstructure effectively deflect cracks, while the {110} slip plane induced by strong textures from multi-pass rolling promoted dislocation slip, thus rendering plastic deformation and weakening the crack tip stress; synergistic interaction is responsible for the improved toughness, resulting in the delamination fracture of the steel. The reduced grain size and M23C6 phases also contributes to the improved toughness.