M2 Steel Research Articles

Evidence of Tribological Adaptation Controlled by Tribosynthesis of FeWO4 on an WC-Reinforced Electron Beam M2 Steel Coating Rubbed against a HSS Disk in a Range of Sliding Speeds.

In the present work, the tribological experiments on sliding the electron beam composite M2+WC coating have been carried out with characterization of the sample microstructures and phases both before and after the testing using metallography, SEM, EDS, and XRD. The sliding in the speed range 0.8-3.6 m/s resulted in simultaneous reduction in both wear rate and coefficient of friction with the sliding speed. Investigations showed that such a tribological adaptation was due to the tribochemical generation of lubricative FeWO4 and Fe2WO6 mixed oxides and the generation of a mechanically mixed composite layer on the worn surfaces that consisted of carbide fragments, an oxidized metal matrix, and was lubricated by in-situ formed mixed iron-tungsten oxides.

Improving mechanical and wear properties of multiphase M50 steel by tailoring bainite morphology

The martensite/bainite multiphase microstructure has shown excellent strength-toughness matching compared with the traditional martensitic microstructure. The ratio of martensite/bainite has always been the focus of performance optimization for the multiphase microstructure. However, the effect of bainite morphology on mechanical properties and wear properties remains unknown. In this work, the microstructure, mechanical, and wear properties of multiphase M50 steel with different bainite morphologies have been investigated. The austempering parameters were controlled to obtain a similar bainite fraction (around 10%) and different bainite morphologies. The microstructure characterization shows that the properly introduced lower bainite can significantly refine the lath structure due to the significant microstructure segmentation effect. When the bundle width and length of lower bainite are respectively 0.107 μm and 3.758 μm, the finest lath microstructure is obtained considering the balance of martensite growth space. The mechanical properties results show that the toughness increases without loss of strength under the tailored bainite. The high-temperature wear performance shows that the multiphase microstructure with tailored bainite results in the decrease of friction coefficient by 42% and a decline of wear loss by 37.9% due to the optimized lubrication layer. This work provides a novel perspective to further improve the mechanical and wear properties of multiphase M50 steel by finely tailoring the bainite morphology on the basis of fixed bainite content.

Исследование микротвердости и структуры инструментальных сталей после ионно-плазменного азотирования в тлеющем разряде

In this paper, the effect of ion-plasma nitriding (IPA) on the microhardness and structure of tool steels is investigated. Samples of HSS M2 and P18 steels, quenched at 1300°Cand then tempered three times at 550°C, were used for the study. The IPA was carried out in a gas mixture consisting of 50% argon, 35% nitrogen and 15% hydrogen at a pressure of 250 Pa and a surface temperature of 400°C, 500°C and 600°C for 3h, 6h and 9h, 9 h. It was found that the highest surface hardness of 1600 HV for HSS M2 steel specimens and 1500 HV for P18 steel specimens were observed after IPA in TR at 500°Cfor 9 h. The maximum hardened layer depth of 120 μm for HSS M2 specimen and 100 μm for P18 specimen were observed after treatment at the same temperature for 6 and 9 hours

Effect of scanning speed on microstructure and properties of 300M steel cladding C276 coating

Effect of scanning speed on microstructure and properties of 300M steel cladding C276 coating

Effect of silicon-doping on the wide-temperature tribological behavior and lubrication mechanism of WC/a-C film

To expand the lubricating temperature range of a-C based film in air atmosphere, a novel Si and WC co-doping Si/WC/a-C film was proposed. The Si/WC/a-C film with different Si contents were prepared by an unbalanced magnetron sputtering system. The effects of Si on the microstructure, thermal stability and mechanical properties of WC/a-C films were explored, and its wide-temperature tribological behaviors against M50 steel were researched at temperatures ranging from 25 °C to 500 °C in air atmosphere. The Si-doping inhibited the crystallization of WC in films, leading to the microstructural transformation from nanocrystalline-amorphous to amorphous. The introduction of Si significantly improved the nanohardness, thermal stability and wide-temperature lubrication properties of WC/a-C film. Therein, the Si/WC/a-C film with 18.85 at.% Si exhibited the best tribological performance featuring the average friction coefficients less than 0.25 at 25–500 °C. Its prominent wide-temperature lubrication performance can be attributed to the successive generation and their combined effect of the self-lubricating phases of sp2-rich carbon, Si–O–C and WO3 in different temperature ranges. Remarkably, appropriate Si-doping can effectively inhibit the oxidation of sp2-rich carbon in tribological layers, thus it is the dominant lubrication phase throughout the wide temperature range of 25–500 °C.

Primary Carbide Refinement in AISI M50 Steel by Dislocation Engineering via Pre-deformation Treatment

Primary Carbide Refinement in AISI M50 Steel by Dislocation Engineering via Pre-deformation Treatment

Effect of Stabilization Treatment on Size and Properties of Austempered M50 Steel

By using SU‐8010 thermal field scanning electron microscope, JEM‐2100 transmission electron microscope, MHRS‐150 Rockwell hardness tester and X‐ray diffractometer to observe the microstructure and detect residual stress, and the measurement of the hardness and the tensile properties, the effect of stabilization treatment on the microstructure, size change, and mechanical properties of the austempered M50 steel is studied. Results show that the residue of austenite and the carbides precipitated during the bainite transformation after austempering lead to lattice shrinkage, which reduces the size of the bearing ring. The release of quenching stress after tempering increases the size. During austempering and tempering, the size fluctuates between −0.29 and 0.23 mm. After the bearing ring is stabilized for 3 times, the precipitation of filamentous carbides reaches the maximum, and the number of carbides does not increase obviously after 5 times of stabilization. The size fluctuation range is −0.9 to 0.7 μm. After M50 steel is stabilized, the transformation of residual austenite to martensite and the precipitation of carbides increase the hardness, and the coarsening of carbides reduces the ductility. The tensile strength increases from 2550 to 2650 MPa, which is related to the dispersion strengthening of carbides and their pinning effect on dislocations.

Effect of Hot Deformation Parameters on Heat-Treated Microstructures and Mechanical Properties of 300M Steel.

The high strength of 300M steel originates from the heat treatment process after forging, but how hot deformation affects the heat-treated microstructure and mechanical properties is unclear. In this study, compression tests under different hot deformation parameters and post-deformation heat treatment experiments were carried out, and the martensite transformation process was investigated using in situ observation. The results show that the grain size of the specimen deformed at low temperature and high strain rate is smaller, and annealing twins will be formed. Both austenite grain boundaries and twin boundaries hinder the growth of martensite blocks, reducing the size of martensite units after heat treatment and thus resulting in higher yield strength. Besides, the mathematical models were established to describe the relationship between hot deformation parameters and grain size after deformation, martensite packet size and martensite block width, respectively, after heat treatment. The relationship between yield strength and hot deformation parameters was also analyzed. According to the results and models, the hot deformation parameters would be optimized more reasonably to improve the final mechanical properties of 300M steel forgings.

Structural Analysis of the Nose Landing Gear of a Fighter Aircraft

The landing gear, which is one of the most important mechanical systems in aircraft, is the structure that is exposed to landing loads, one of the most important and critical loads that the aircraft is exposed to throughout its life cycle. In addition to the fact that the landing gear system must have high strength to these loads, long life, high performance, low volume, minimum weight, and low cost are important criteria. For this purpose, the optimum design is created by making a structural analysis using the landing gear finite element method. The main purpose of this study is to analyze the strength criteria by performing the structural analysis of the nose landing gear of a fighter aircraft. For the design, the most critical static and dynamic loads in the landing condition were calculated and applied as vertical, side, and drag forces. The displacement and stress values obtained as the final result by using metallic materials such as Aluminum 7075 T6 alloy, Titanium Ti-6Al-4V alloy, PH13-8Mo, 300M Steel, SAE 1035, and AISI 4340 steel alloy in the nose landing gear fork, torque links, side stay arms, and main strut were compared. The safety of the parts was examined from the results of the analysis. CAD drawings were made using Siemens NX and ANSYS SpaceClaim program. Structural analysis was applied with the ANSYS Workbench program, which uses the finite element method.

Hot workability and microstructure evolution of wire arc additive manufactured 300M steel

Wire arc additive manufacturing (WAAM) technology offers a material-saving and efficient method of manufacturing the 300M steel components, but the obtained microstructure and properties hardly reach the level of wrought materials. By combining WAAM technology with forging process, a novel forming process is proposed. The preferred shape pre-forgings are easily prepared, and the number of forging steps significantly decreases. The WAAMed as-cast microstructure also can be transformed into the wrought state by the proposed forming process. The aim of this study is to investigate the hot deformation behavior and microstructure evolution of WAAMed 300M steel under various deformation temperatures and strain rates. The results show that the WAAMed 300M steel exhibits a higher plastic deformation resistance than the wrought 300M steel. With the increase of deformation temperature and strain rate, the difference of flow stress between the WAAMed and wrought 300M steel decreases. The hot deformation activation energy of WAAMed 300M steel is calculated as 374.1 kJ/mol, which is much higher than that of wrought 300M steel (332.3 kJ/mol). The possible processing windows obtained from the hot deformation activation energy maps are 1040-1120 °C/0.01-10 s−1 for the WAAMed 300M steel and 1010-1130 °C/ 0.1-10 s−1 for the wrought 300M steel. The constitutive model considering strain compensation is established to describe the hot deformation behaviors of WAAMed and wrought 300M steel. The high correlation coefficient and low average absolute relative error confirm the suitability of the developed constitutive models for predicting the flow stresses of WAAMed and wrought 300M steel.

Effect of different heat input on the microstructure and mechanical properties of laser cladding repaired 300M steel

Laser cladding repair technology is valued for its ability to repair of damaged parts with high performance. However, there are so many parameters affect the repair quality that it takes a lot of work to determine the optimal parameters. In this article, a variety of parameters were combined as dimensionless heat input (Q∗), and the effect of Q∗ on the microstructure and mechanical properties of 300M steel repaired samples were studied. Results showed that with the increase of Q∗, microstructure of heat affected zone transformed from tempered martensite to tempered martensite and low bainite. The microstructure of the repaired zone transformed from untempered martensite to untempered martensite and a small amount of retained austenite. With increasing of Q∗, residence time above the austenitizing temperature was extended, and more uniform microstructure were obtained in the repaired zone. What's more, at Q∗ = 5.1, the repair efficiency increases twice than Q∗ = 1. The tensile strength of the repaired samples reached 1017.6 MPa and the elongation reached 6.9%, which were far lower than that of forged samples. The heat treatment was carried out on the repaired parts, which eliminated the microstructure difference due to different Q∗. Compared with the repaired samples without heat treatment, the tensile strength increased by 75% to 1783.8 MPa and the elongation increased by 86% to 10.4%.

Flow Stress Characteristics and Constitutive Modeling of Typical Ultrahigh‐Strength Steel under High Temperature and Large Strain

Hot compression experiments are conducted to explore the deformation behaviors of 300M steel under large strain, which can mimic the forging process of large components. It is found that the variations of flow stress are affected by the deformation parameters and the rivalry between work hardening and dynamic softening. A novel constitutive model is proposed to forecast the flow stress at different deformation parameters. The Pearson correlation coefficient between the experimental flow stress and the predicted flow stress by the newly proposed constitutive model is 3.489%, and the relative error is within the range of ±5%. It implies that the newly proposed constitutive model can describe the variations of flow stress appropriately. Furthermore, the prediction accuracy of the newly proposed constitutive model is compared with that of the strain‐compensated Arrhenius constitutive model, the modified Johnson–Cook constitutive model, and the Hensel–Spittel constitutive model. Results demonstrate that the novel constitutive model provides the highest accuracy, followed by the strain‐compensated Arrhenius constitutive model, then the Hensel–Spittel constitutive model, and the modified Johnson–Cook constitutive model has the weakest accuracy. The establishment of the novel constitutive model is helpful in accurately predicting the flow behavior of materials during the forging process.

Effect of Short-Time Carburizing Treatment on Microstructure and Mechanical Properties of M50 Steel

Effect of Short-Time Carburizing Treatment on Microstructure and Mechanical Properties of M50 Steel

Study on the surface integrity distribution of 300M ultrahigh strength steel subjected to different surface modification treatments

The surface integrity of 300M steel subjected to shot peening (SP), laser shock peening (LSP), ultrasonic surface rolling process (USRP), and hybrid laser shock peening with ultrasonic surface rolling process (LSP + USRP) processes were compared. The results indicate that USRP and LSP + USRP generate a smooth surface with Ra in the range of 0.05 μm ~ 0.10 μm while SP and LSP increase the Ra magnitude regarding grinding by 56.5 % and 18.8 %, respectively. Severe plastic deformation is introduced on the treated specimens, owing to which a gradient microstructure with nanostructured grains at the topmost surface (320 nm ~ 1130 nm in thickness) is observed. The depth of the compressive residual stress layer after SMTs achieves in the range of 200 μm ~ 2000 μm, of which the LSP + USRP generates the maximum value. The magnitude of surface compressive residual stress significantly increases compared with the control sample, which locates in the range of −709 MPa ~ −1167 MPa. An obvious work hardening is characterized after SMTs, of which the SP process presents a 31.2 % increase in the magnitude of surface microhardness and LSP + USRP holds the deepest hardening layer of 600 μm ~ 700 μm. Comparing the single SMT, the hybrid LSP + USRP treatment was found to be the most effective surface modification technique.

Influence of vacuum graded austempering treatment on microstructure and mechanical properties of M50 steel

By means of microstructure observation and mechanical property tests, the effects of vacuum graded austempering treatment on carbide precipitation, bainite transformation, hardness and impact toughness of M50 steel were studied. Results show that after the steel was vacuum grading treated at 560 °C for 10 min, 20 min, 30 min and 60 min and austempered at 200 °C for 2 h, the microstructure is mainly composed of martensite, acicular lower bainite, retained austenite, and carbides (C) in different shapes. With the extension of the grading time from 10 min to 60 min, the content of precipitated carbides after austempering treatment increases from 2.38% to 3.79%, that of the lower bainite increases from 13.14% to 16.03%, and the hardness decreases from 65.06 HRC to 64.26 HRC. After tempering treatment at 550 °C × 2 h for 3 times, the content of precipitated secondary carbides increases from 3.86% to 5.37%, and the hardness of the steel decreases compared to the corresponding austempered steel. Thereinto, the hardness of the tempered steel with the grading time of 20 min is the highest to be 62.92 HRC. After vacuum grading treatment at 560 °C × 10 min, austempering and tempering treatments, the impact toughness of the M50 steel is 16.63 J/cm2, which is enhanced by 50.6% compared to the steel only with vacuum quenching and tempering. This is related to the formation of bainite after graded austempering treatment and the uniform precipitation of fine carbides after tempering.

Evaluación de métodos de medición destructivos y no destructivos para determinar el espesor de un recubrimiento de titanio depositado por evaporación física

The purpose of this research is to develop reference Ti-coatings and analyze the thicknesses evaluated via destructive (DT) and non-destructive (NDT) measurement techniques. The Ti coating was deposited on a mirror finished AISI M2 steel by the magnetron process. The nominal value of the coating thickness was 1 μm. The NDT was the X-Ray Fluorescence (XRF) method, the thickness for the portable analyzer was 1.18 ± 0.19 μm and the thickness using the spectrometer XRF was 1.17 ± 0.24 μm. For DT, thickness measurements were carried out in the cross-sections of the Ti-coatings, using the Field Emission - Scanning Electron Microscopy equipped with Energy Dispersive Spectrometer (FE-SEM-EDS). The coating thickness measurements were performed with image analysis of secondary electrons (SE), backscattering electrons (BSC), mapping (MAP) and elemental profiles (LS) using ImageJ and Aztec software. The results of the thickness measurements are SE: 1.12 ± 0.15 μm, BSC: 1.14 ± 0.13 μm, LS: 1.25 ± 0.13 μm and MAP: 1.29 ± 0.6 μm. Variations in the results were identified and estimated in the uncertainty models proposed for each method.

Influence of various counter-bodies on the sliding friction and wear response of M50 steel

ABSTRACT The primary aim of the present investigation is to evaluate the sliding wear response of M50 steel against three different counter-bodies as function of applied load and sliding velocity. The investigation is essentially undertaken to understand the sliding friction of hybrid bearing and ordinary bearing used in spacecraft and aeroengine. Towards that purpose, M 50 steel was made to slide against three different counter-bodies such as M50 steel, 52100 steel and Si3N4, at three different applied loads and at three different sliding velocities. The results show that the friction coefficient of M50 steel decreases with the applied load and the sliding velocity against all types of counter-bodies. The wear rate of M50 steel against Si3N4 counter-body increases with the applied load and the sliding velocity. In contrast, the wear rate is generally independent of the applied load and the sliding velocity against 52100 steel and under self-mating condition.

A novel ReN/TiAlN multilayer coating on M2 steel by magnetron sputtering: Development and electrochemical behavior

By DC magnetron sputtering ReN and multilayers of TiAlN/ReN films were produced. The coatings were deposited onto high-speed steel (AISI M2) samples and silicon wafers. Analysis of the microstructure and phase composition showed that the ReN monolayer, which was the same as the coating used subsequently for the manufacture of the multilayers of TiAlN/ReN, possessed a cubic crystalline structure. The ReN coating had preferential columnar growth in the direction of the plane (111) and presented precipitates of the rhenium oxides ReO2 and ReO3. A detailed study of the electrochemical behavior and corrosion resistance of the coated steel substrate as a function of the number of TiAlN/ReN bilayers was carried out using electrochemical impedance spectroscopy and polarization measurements. The coatings exhibited a relative high hardness and Young's Modulus, and a better performance against corrosion in aqueous media rich in chlorine ions when the bilayer number and period were 5 and 221.2 nm, respectively. It was observed that the formation of rhenium oxide particles influences the electrochemical behavior of coatings.

Droplet size dependent localized corrosion evolution of M50 bearing steel in salt water contaminated lubricant oil

Corrosion of M50 steel in salt water contaminated lubricant oil (SCO) were systematically studied in combination with settling dynamics of droplet and characterization of localized corrosion area (LCA). Results show that LCA on steel surface existed in two forms: eye-like LCA and isolated outer zone. Larger outer zone was more likely to create and enlarge inner zone inside it. Outer zone actually resulted from larger droplet, because larger droplet had higher approaching velocity in oil, allowing longer duration at stabilization stage. Underlying formation mechanisms of sunken inner zone and bulging outer zone were respectively given as galvanic and uniform corrosion.

A novel quenching-electroshocking-tempering process for toughness improvement by microstructure refining and austenite stability tailoring in aviation bearing steel

In this work, the microstructural evolution and mechanical properties of aviation M50 steel under a novel quenching-electroshocking-tempering (Q-E-T) process were investigated. Microstructural observations indicate that the carbon concentration and volume fraction of retained austenite (RA) in Q-E-T specimens are higher than those in conventional quenching‐tempering (Q‐T) specimens due to the significant carbon partition induced by the introduced electroshocking treatment (EST). Meanwhile, the diameter of packets in the Q-E-T specimens is refined from 1.71 μm to 1.34 μm, which is attributed to the segmentation of blocky as-quenched RA by bainite transformation during EST. The mechanical analysis shows that an excellent combination of ultimate tensile strength and impact toughness is achieved for M50 steel subjected to the Q-E-T process. Compared with the conventional Q-T process, the impact absorbing energy of M50 steel is increased by 24.1% without any loss of tensile strength. Additionally, the thermal and mechanical stabilities of RA in the Q-E-T specimens are both improved. This work provides a novel strategy for improving the impact toughness of M50 by refining the microstructure and appropriately tailoring the stability of RA via an efficient Q-E-T process.