M2 High Speed Steel Research Articles

Surface modification of high-speed steel (HSS) drills by plasma nitriding and cathodic cage tin deposition

Cutting tools made of high-speed steel have significant economic and technological importance. To enhance their productivity, thermochemical treatments are sought to improve both surface mechanical and tribological properties. Plasma nitriding and thin film deposition are widely employed for this purpose. In this study, modifications were made to M2 high-speed steel drills through plasma nitriding at temperatures of 400°C and 450°C. Cathodic cage TiN plasma deposition was also performed, varying the dwell time at a fixed temperature of 450°C. Characterization techniques included optical microscopy, X-ray diffraction (XRD), Vickers microhardness testing, and scanning electron microscopy (SEM). Performance tests were carried out to evaluate the behavior of the drills in relation to wear when machining AISI 1020 steel. It was observed that longer deposition times promote more uniform and thicker layers, and higher nitriding temperatures result in thicker nitride layers. An increase in hardness was noticeable in all deposition and nitriding treatments, with the nitrided samples exhibiting the highest hardness. During performance tests, the cathodic cage plasma TiN deposition demonstrated greater potential for application in HSS drills, with a treatment lasting 4 h providing the best results.

Eutectic resolidification and ultrafast self-quenching of the microstructure in the surface layer of high-speed steel by scanning electron beam treatment

Improving the service life and efficiency of high-speed steel (HSS) tools remains a formidable challenge. Herein, scanning electron beam (SEB) was employed to modify the surface of M2 HSS. Results revealed that SEB induced eutectic resolidification and ultrafast self-quenching of microstructure in surface layer of HSS. The melted layer exhibited a microstructure comprising martensite, residual austenite, dispersed finely rod-like MC and lamellar M2C eutectic carbides along grain boundaries. Martensite and eutectic carbide grid structure significantly enhanced the hardness and wear resistance of surface layer. Compared to substrate, the microhardness of SEB sample was elevated by more than threefold, reaching 914.7HV0.2, which exceeded the hardness (828.6HV0.2) of conventional quenching treatment. Notably, the wear volume of SEB sample had been reduced to 0.54 × 10−11 m3, resulting in a wear resistance that was 3.8 times greater than that of quenched sample.

The Inclusion Characteristics and Mechanical Properties of M2 High-Speed Steel Treated with a Vacuum Carbon Deoxidation Process

The oxygen content of M2 high-speed steel has not been intentionally controlled in industrial production through secondary refinement in vacuum furnaces. However, a lower oxygen content has a significant effect on the cleanliness, toughness, and addition of rare-earth elements to M2 high-speed steel. The changes in total oxygen content controlled by vacuum carbon deoxidation (VCD) treatment and inclusion evolution were investigated in M2 high-speed steel to understand the effects of carbon on dissolved oxygen and oxides in the carbon–oxygen (C-O) reaction process. Furthermore, the microstructure and properties of M2 high-speed steel caused by vacuum insulation and the role of reducing oxygen content in rare-earth alloying were briefly demonstrated. The results showed that the [O%] decreased from 30 ppm to 3 ppm in a vacuum at holding times above 25 min through the C-O reaction, leading to an inclusion reduction of approximately 70%. In the case of [O%] = 3 ppm in M2 high-speed steel, the addition of rare-earth elements has a greater effect on the inclusion characteristics. Lowering the oxygen content of M2 high-speed steel improves cleanliness and plays a significant role in rare-earth alloying.

Growth kinetics of Fe2B layer formed on the surface of borided AISI M2 high-speed steel

Abstract In this study, the growth kinetics of the Fe2B layer was investigated and formed on the surface of borided AISI M2 high-speed steel. Boriding treatments carried out by the pack-boriding method were carried out using Ekabor 2 boriding agent at 1,173, 1,273, and 1,373 K for 2, 4, and 6 h. After the boriding processes, the samples were prepared metallographically and their microstructures were examined with the help of backscattered electrons (BE) by scanning electron microscope (SEM). Following SEM examinations, microhardness measurements were carried out from a single sample using 100 g with the Vickers indentation method to understand whether the layer hardness was compatible with Fe2B. When the results of the experimental studies are compared with the results of the literature, it has been determined that AISI M2 high-speed steel can be borided and the boride layer formed on the surface is single-phased (Fe2B), unlike that formed on many other steel types. After determining that the layer formed on the borided AISI M2 surface is single-phase Fe2B, the growth kinetics calculations of this phase were carried out with the help of the Arrhenius equation.

Exploring the impact of cryogenic treatment on detonation spray coated M2 high speed steel

ABSTRACT An Al₂O₃–13% TiO₂ coating was applied to M2 high-speed steel using the d-gun process. The surface properties were compared between uncoated samples, coated samples before cryogenic treatment (CBCT), and coated samples after cryogenic treatment (CACT). The mean particle size was ~17.07 μm, with average coating thicknesses of 212 μm for CBCT and 196 μm for CACT. CACT exhibited 3.19% and 24.65% higher microhardness than CBCT and uncoated samples, respectively. All samples exhibited hydrophilic wettability, with CBCT showing 59.41% and 67.43% higher Ra values, along with 56.03% and 59.70% higher Rz values than CACT and uncoated samples. CBCT also exhibited 32.96% and 98.14% higher porosity than CACT and uncoated samples. CACT showed reduced abrasion loss by 54.05% and 36.25% compared to CBCT and uncoated samples. CBCT has better corrosion resistance of 90.25% and 95.89% than CACT and uncoated samples. The Raman shift revealed increased particle size formation in CACT than other samples.

Effect of heat treatment on microstructure and wear properties on Binder Jetting Additive manufactured M2 High-Speed steel

In this study, the influence of heat treatments (annealing at 1175 °C, sub-zero at −80 °C, and triple tempering at 565 °C) of Binder Jet Additive Manufactured (BJAM) M2 grade HSS on the microstructure and tribological properties are investigated and were compared with that of conventionally manufactured samples. The residual austenite was transformed into martensite phase upon heat treatment. The tribological analysis was performed using a pin-on-disc experiment for 40 N, 50 N, and 60 N loads. It was observed that the heat-treated BJAM samples exhibited 11.5 %, 7.5 %, and 5.5 % higher specific wear resistance compared to the as-sintered samples. The enhancement in the wear resistance is primarily due to the presence of metal carbide precipitates in the heat-treated sample.

The effects of deep cryogenic treatment on PVD-TiN coated AISI M2 high speed steel

In this study, the effect of deep cryogenic treatment (DCT) on PVD-TiN coated AISI M2 high speed steel was investigated. DCT has been cited to improve hardness, toughness, and wear resistance in martensitic steels. Despite these promising results, there is limited published work on the effects of DCT on hard coated steels, such as industrial cutting tools. Hence, the aim of this study is dedicated to providing experimental data on the effects of PVD-TiN coated AISI M2 high speed steel subjected to DCT. A combination of microstructural and mechanical techniques, such as optical and scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), nanoindentation hardness and scratch testing have been applied to determine the changes observed. The result of the nanoindentation hardness showed that an improved result in terms of hardness and elastic modulus were obtained for DCT coated test samples with increases of 5.2 % and 14.8 % compared to conventionally prepared coated non-DCT samples. Upon further examination, it was interesting to note that there was a significant change of 14.8 % in the elastic modulus of the DCT coated samples as compared with the untreated samples. The reason for the difference could be attributed to the contribution of the substrate or changes in the substrate due to DCT.For adhesion testing, optical and SEM examination revealed that DCT coated samples exhibited promising results as the transverse cracks observed for the DCT coated samples appeared denser, more extensive, and could suggest good adhesion as when the mechanical work is applied, energy is better absorbed rather than coating flaking. A comparison of the critical failure points (Lc) revealed that DCT coated samples had Lc values 3.62 % high than the conventionally prepared samples, which could be attributed to the elastic modulus mismatch between the coating and substrate.

Electrochemical corrosion and product formation mechanism of M42 high-speed steel in NaH2PO4-Na2SO4 passivating electrolyte

High-speed steel (HSS) rolls operate in harsh conditions, making them vulnerable to surface degradation. Material removal technology for repairing defective HSS roll surfaces is the most effective way to maintain their integrity and reduce production costs. Electrochemical corrosion machining, with its excellent machining capabilities, offers a promising method for repairing HSS roll surfaces. However, the outer working layer of these rolls is made of premium HSS containing passivating metallic elements, complicating its corrosion behavior, particularly in passivating electrolytes. To elucidate the corrosion behavior and uncover the underlying mechanisms of corrosion and product formation of HSS during electrochemical corrosion machining, this study investigates the electrochemical corrosion process and behavior of M42 HSS used in rolls within a NaH2PO4-Na2SO4 passivating electrolyte. Metallographic etching experiments indicated that M42 HSS comprises a tempered martensitic matrix along with M2C and M6C eutectic carbides. Characteristics of oxidative reactions for M42 HSS in the electrolyte were observed in cyclic voltammetry. By conducting anodic polarization tests, along with thermodynamic analysis and characterization techniques, the entire electrode system was thoroughly examined, including corrosion phenomena, varying processes, and underlying mechanisms of corrosion and product formation. Notably, this study is the first to construct a Pourbaix diagram for the M42 HSS-H2PO4−-SO42−–H2O system. The thermodynamic analysis revealed that the applied potential variation significantly influences corrosion behavior of M42 HSS, confirming by the characterization results. The adsorption phenomenon on the cathodic surface requires a higher potential (such as 6 V) to occur. Electrochemical reactions primarily occur on the anodic surface, while the cathodic surface (or in the electrolyte) mainly engages in chemical reactions with no electronic participation. Furthermore, the electrochemical corrosion process of HSS is driven by one or more corrosion mechanisms, such as galvanic corrosion, pitting, or intergranular corrosion. Therefore, these findings from this study contribute to the development of repairing HSS roll surfaces based on electrochemical corrosion machining in future engineering applications.

Homogenization Treatment and Plastic Deformation Improve the Carbide Homogeneity of M42 High‐Speed Steel

The mechanical properties of high‐speed steel (HSS) are significantly influenced by the distribution of carbides formed during solidification. Despite extensive research, the nonuniform cooling in large ingots remains an area requiring further investigation. In this study, the microstructure inhomogeneity in M42 HSS with a diameter of 330 mm is examined. Models are developed to predict the dissolution of carbide networks during homogenization, achieving a 39% reduction in hardness variation (Δr) between the center and surface. Further improvements are attained through hot forging and rolling, leading to the fragmentation of the carbide network into a banded structure. Additionally, a detailed carbide tip dissolution model is established, providing a reliable basis for optimizing annealing processes. As a result, the carbide distribution converges significantly, with hardness variations reduced by 88% to only 0.3 hardness Rockwell C scale, showcasing substantial enhancement in material homogeneity.

The Effect of Boriding Temperature and Time on the Structural and Mechanical Properties of M42 Steel

In this study, the effect of boriding temperature and time on the structural and mechanical properties of M42 high speed steel were investigated. Samples placed in Ekabor II powder were exposed to pack boriding treatment at 900°C and 1000°C for 4 hour and at 950°C for 2, 4 and 6 hours. Scanning electron microscope (SEM) images indicate that boron diffuses into the samples and a sawtooth-like cross-sectional morphology is formed. The presence of boron has also been proven by Energy Dispersive X-ray spectrometry (EDX). In addition, it was determined that boron layer thickness increased with increasing boriding temperature. When the microhardness values were examined, it was observed that the sample borided at the highest temperature had the highest hardness value and the hardness values decrease with the decreasing of boriding temperature. Similar results were also obtained regarding the boriding time. The highest microhardness and layer thickness values were obtained after 6 hours of boriding. Additionally, it was observed that the hardness values of borided samples decreased as they moved from the surface to the inner parts.

Duplex Surface Modification of M2 High-Speed Steel

Duplex Surface Modification of M2 High-Speed Steel

Study the variation of current density & corrosion behavior of modified M2 tool steel: Simulation & experimental

In this study, the simulation of the current density was carried out through COMSOL Multiphysics on surface-modified M2 high-speed tool steel. The results demonstrated that in the presence of the nitride layer on the surface of M2, the current density was increased remarkably in the nitride layer and M2 was immune, and consequently, it can be predicted that the corrosion resistance was increased. For verification, the surface modification through plasma nitriding was applied on the M2 steel corrosion resistance and was evaluated through polarization and electrochemical impedance spectroscopy (EIS) in the 3.5 wt% of NaCl solution. The results confirmed the simulation outcomes; therefore, optimization of the parameters was performed. The impression of the variation of the process parameter of plasma nitriding such as temperature (500, 550, and 600 °C), time (4, 6, and 8 h), and ratio of inserted gases (N2/H2: 1:3, 1:1, 3:1) on the growth of the diffusive layer was assessed by X-Ray Diffractometry (XRD). Outcomes illustrated that applying plasma nitriding causes the formation of the different nitride phases on the top surfaces of the M2 substrate and Fe3N is the dominant phase. The diffusive nitride layer has a higher current density based on simulation results. The microhardness of the surface increased remarkably and 2414 HV was reached as a maximum surface hardness. By considering the obtained results, 500 °C, 6 h, and a ratio of 1:1 of N2/H2 were chosen as optimum conditions of the plasma nitriding of M2 high-speed tool steel, and a corrosion rate of 1.62 mpy was calculated.

Effect of nano-SiC on microstructure evolution and enhanced high wear resistance mechanism of laser surface alloyed M42 high-speed steel

M42 high-speed steel is one of the main materials for preparing bimetallic band saw parts. In this paper, nano-SiC particles of different densities (0–1.00 mg/mm2) were precoated on the surface of M42 high-speed steel samples, then, the samples were prepared by laser alloying. The matching relationship between the quantity, size, and type of martensite and MxCy carbides in laser alloyed samples play a decisive role in improving wear resistance. It is found that under the optimized particle density of 0.75 mg/mm2, compared with M42 high-speed steel, the hardness was increased by 50%, the wear rate decreased by 84.7%. The matching relationship between Martensite and MxCy carbides formed by laser alloying of nano-SiC particles on the improvement of wear resistance was elucidated.

Effect of Cryogenic Time on Wear Resistance of M2 High Speed Steel

The wear resistance, residual austenite volume and carbon content in martensite of M2 steel were studied by means of universal vertical friction and wear testing machine, X-ray diffractometer (XRD), scanning electron microscope (SEM) and digital Rockwell hardness tester. The results show that a large number of fine carbide particles in M2 steel martensite are precipitated by cryogenic treatment and distributed uniformly and diffusely in the structure. With the increase of cryogenic time, the residual Austenite volume of M2 steel gradually decreases, while the Martensite volume increases, resulting in the wear resistance and Rockwell hardness increasing first and then decreasing. After 24 hours of cryogenic treatment of M2 steel, its wear resistance increased by 310%, hardness increased by 3.6%. Therefore, 24 hours is confirmed as the best cryogenic treatment time for the wear resistance and hardness of M2 steel.

Effect of Tungsten Carbide Additions on the Microstructure, Mechanical, and Tribological Properties of M2 High-Speed Steel Matrix Composites

Effect of Tungsten Carbide Additions on the Microstructure, Mechanical, and Tribological Properties of M2 High-Speed Steel Matrix Composites

A modified M2 high-speed steel enhanced by in-situ synthesized core-shell MC carbides

A modified M2 high-speed steel enhanced by in-situ synthesized core-shell MC carbides

Wear and corrosion behavior of TiC and WC coatings deposited on high-speed steels by electro-spark deposition

Abstract Electro-spark deposition (ESD) is one of the most effective methods for improving the surfaces of metallic materials by applying ceramic-based cermet coatings. In this study, TiC and WC coatings were deposited on the surface of AISI M2 high-speed steel using the ESD method. Subsequently, the coated surfaces were examined through microstructure, phase structure, microhardness, friction, wear, and electrochemical corrosion tests, and compared with untreated AISI M2 steel. The TiC and WC phase coatings obtained with ESD resulted in a significant improvement, with hardness levels exceeding four times that of AISI M2 steel, leading to reduced wear volume losses and friction coefficients. Furthermore, the cermet coatings formed on the surface exhibited 2–3 times improvement in corrosion resistance due to their lower conductivity. This study demonstrates that WC coatings may offer a more effective solution for enhancing the wear resistance of AISI M2 steel, while TiC coatings could be more effective in improving corrosion resistance.

Development of Multi-Component B-C-N Diffusion Coating on Wrought AISI M2 High-Speed Steel Substrate

The present investigation has been carried out to study the microstructure evolution and microhardness of the multi-component B–C–N diffusion coatings developed on wrought AISI M2 high-speed steel substrate at 560 and 650 °C for 1 and 4 h for both temperatures. The microstructure of the coatings was studied using scanning electron microscopy, energy dispersion spectroscopy and X-ray diffraction analysis. Vickers microhardness measurements were also performed. The investigations showed that varying conditions of the thermochemical treatment resulted in a variety of coatings which exhibited varying microstructure, phase composition and microhardness.

Microstructure evolution and properties of laser cladding AlFeCrMoNbx refractory high entropy alloy coatings

Refractory high-entropy alloy (RHEA) has superior mechanical properties but low room-temperature ductility. However, eutectic heterostructure alloy has strength-ductility trade-off. In this study, the AlFeCrMoNbx (x = 1, 1.2, 1.4, 1.6, 1.8, and 2.0) RHEA coatings were successfully prepared on the surface of an M2 high-speed steel (HSS) by laser cladding. The increase of Nb content promoted the formation of eutectic microstructure, the coating changed from hypoeutectic structure to hypereutectic structure. When x = 1.8, the coating exhibited a near-eutectic structure consisting of BCC and Laves phases with high hardness and wear resistance. After annealed at 750 °C for 8 h, the phases and microstructure of Nb1.8 REHEA coating did not change, contributing to a high microhardness and wear resistance. With annealing temperature rising, the microhardness and wear resistance decreased. After annealing at 1050 °C, the hardness of the coating still remained 549 HV0.2, indicating a good high-temperature softening resistance of REHEA coating.

Effect of Surfactant Tellurium on the Microstructure and Mechanical Properties of M42 High-Speed Steel

Effect of Surfactant Tellurium on the Microstructure and Mechanical Properties of M42 High-Speed Steel