AISI M2 High Speed Steel Research Articles

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.

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.

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.

New insights into the microstructure of M2 high-speed steel

In this work, the microstructure of the heat-treated AISI M2 high-speed steel of different initial structural states, wrought and as-cast, was investigated in detail down to the atomic scale, using advanced electron microscopy techniques. Significantly different amount of the secondary carbide particles of a size up to 300 nm in the microstructure of both steels was established and described. In the tempered matrix, the formation of the ultrafine sub-grains with a size in the range of 3–15 nm and the substructure of the α-Fe consisting of nano-sized elongated plates about 200–300 nm in length and 7–30 nm in thickness were proven. Fine dispersions of the secondary hardening carbides along the matrix sub-grain boundaries and inside the carbide clusters were thoroughly investigated and identified as vanadium-rich MC carbide. Extremely fine precipitates at the boundaries of the nano-sized elongated plates in the substructure of the tempered α-Fe were revealed in both steels. The precipitates, regularly dispersed in the tempered matrix and containing carbon, were enriched primarily in iron, molybdenum, chromium, vanadium, and, to a lesser extent, in tungsten, as proven by the combined EDX and EELS analysis. At the atomic scale, the precipitates were found to be mostly disordered solids without a crystalline structure. However, some of the precipitates exhibited traces of crystalline structure, which likely corresponds to Fe21(W,Mo)2C6 phase.

Optimisation of Thermochemical Treatment of M2 High-Speed Steel

The present study has been undertaken to study the microstructure and microhardness of the multi-component B–C–N diffusion coatings developed on AISI M2 high-speed steel substrate at 560 and 650 oC for 1 and 4 h for each temperature respectively. The investigation of the coatings was fulfilled using scanning electron microscopy, energy dispersion spectroscopy and X-ray diffraction analysis. Additionally, Vickers microhardness measurements were performed. The results showed that varying conditions of the thermochemical treatment led to a variety of coatings in the sense of their microstructure and phase composition.

Effects of TiN/CrN, CrAlN, and TiN Coatings on the Performance of AISI M2 Tool Steel

The aim of this study is to investigate the effects of various ceramic-based coatings on the performance of AISI M2 high-speed steel punch used in the nut piercing process. AISI M2 punches were coated with TiN, TiN/CrN, and CrAlN utilizing a physical vapour deposition method. The total stroke number of the punches was used to evaluate the tool life of TiN, CrAlN, and TiN/CrN coated AISI M2 punches. AISI M2 punch coated with TiN/CrN was able to work up to greater stroke numbers than punches coated with TiN and CrAlN. Hardness and wear tests were performed to study the wear resistance of TiN/CrN and CrAlN coatings under relatively normal load conditions compared to actual working conditions (impact loading conditions) in the piercing process. The hardness and wear resistance of the CrAlN coating were greater than those of the TiN/CrN coating. The wear performance of the CrAlN coating was higher at normal loads and sliding speeds while the tool life of the TiN/CrN-coated punch was better under impact loading conditions.

Significant Improvement of Cleanliness and Macro/Microstructure of As-Cast AISI M42 High-Speed Steel by Mg Treatment

Significant Improvement of Cleanliness and Macro/Microstructure of As-Cast AISI M42 High-Speed Steel by Mg Treatment

A novel printable high-speed steel filament: Towards the solution for wear-resistant customized tools by AM alternative

Additive manufacturing (AM) alternative technologies, including Fused Filament Fabrication (FFF), offer the possibility to produce both prototypes and low-volume production metallic components. This is the first time that AISI M2 high-speed steel powder is processed by FFF, achieving near full density in a complementary way to Powder Injection moulding (PIM), yet reducing the investment cost and the lead time. A completely optimized FFF process is presented: from the design of a printable highly filled metallic filament that can be fed into conventional 3D printers, to high-quality green parts that are properly debound and sintered. The final specimens (99.6% densified) are thermally treated (one quenching and two tempering) and, then, evaluated in terms of scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and mechanical characterization (hardness and wear resistance). The effect of the processing technology and the heat treatments are discussed, validating the feasibility of FFF to develop customized high-speed tools with superb performance at a competitive cost.

Design, manufacturing and plasma nitriding of AISI-M2 steel forming tool and its performance analysis

Mechanical manufacturing processes aim to transform metallic materials into mechanical parts and components. In these processes, tools are used for cutting, punching and stamping. The ending of the useful lifetime of these tools happens with wear of its cutting edge. Such forming tools can be manufactured by several materials including AISI-M2 high-speed steel steels, and their surface properties can be modified by thermal and thermochemical treatments. In this study, an attempt is made to design and manufacture a forming tool in the laboratory without usage of computer numerical control machines. Afterwards, the manufactured forming tools are plasma nitrided at various temperatures (400–500 °C) and obtained results are compared with existing tool provided by nails manufacturing factory. The forming tools after plasma nitriding show a significant hardness improvement, increased nails production (used in civil construction), and better wear resistance as compared to the existing tool, particularly at 400 °C. The forming tool obtained in this study is easy-to-manufacture, eco-friendly plasma treatment and cost-effective, and thus it is expected that it can resolve company's technical issue regarding premature wear and tear, and rapid replacement of tool in nails manufacturing.

Evolutions of Micro- and Macrostructure by Cerium Treatment in As-Cast AISI M42 High-Speed Steel

The as-cast M42 high-speed steels containing different contents of cerium (Ce) were manufactured to investigate the effects of Ce on the solidification structures at the micro- and macroscale. The results indicate that the addition of Ce could modify MgO·Al2O3 and MnS into the Ce-containing inclusions. The addition of Ce refined the dendrite structure and eutectic carbides, which can be ascribed to the heterogeneous nucleation of primary austenite on Ce2O2S or Ce2O3 and the increase in both the compositional supercooling at the dendrite forefront and the restriction on the dendrites coarsening. Both the secondary dendrite arm spacing (SADS) and total eutectic carbides content decrease gradually with increasing Ce content. M2C and M6C carbides are the predominant precipitates. The increase of Ce content made the morphology of M2C carbides change from long lamellar or straight-rod morphology into shorter curved-rod or honeycomb morphology because of the overgrowth of eutectic austenite, but it had no significant effect on the morphology of M6C carbides. Ce2O2S and Ce2O3 can serve as the very effective heterogeneous nucleation sites for M6C carbides because of the low lattice disregistry between them, hence Ce addition improved markedly the macroscopic distribution of M6C carbides in the cast ingot and promoted the formation of M6C carbides at the expense of M2C carbides.

Influence of C content on the structure, mechanical and tribological properties of CrAlCN films in air and water-based cutting fluid

CrAlCN films with different C concentrations ranging from 0 to 75.3 at% were deposited on AISI M2 high-speed steels using magnetron sputtering. Besides their structure and mechanical properties, the tribological performances of CrAlCN films in air and water-based cutting fluid were also compared. The results showed that CrAlN film consisted of most fcc-CrN/Cr2N and less fcc-AlN. After C incorporation, the amount of fcc-CrN/Cr2N in CrAlCN films still kept stable relatively in addition to the more formation of amorphous carbon (a-C). As a consequence, the hardness of CrAlCN films increased firstly to the highest value of 1095.2 ± 56.8 HV0.01 at the C content of 50.3 at%, but then declined slightly. However, the critical loads of CrAlCN films decreased gradually from 14.8 ± 2.7 to 7.9 ± 0.9 N as the C content increased from 0 to75.3 at%. High C content in CrAlCN films resulted in the more formation of a-C, thus contributing to a decrease in friction coefficient of CrAlCN/SUS440C tribopairs both in the air (from 1.06 to 0.47) and water-based cutting fluid (from 0.60 to 0.11). In the meantime, the CrAlCN film containing the highest C content (75.3 at%) showed the minimum wear rate because of the lowest friction coefficient in both friction environments. As compared with the tribological performances of CrAlCN films in air, the CrAlCN films were more suitable to be used in water-based cutting fluid condition.

Study of the impact of the lubricant-cooling agent with the diamond graphite submicropowder additive on the durability of AISI M2 steel drill bits

The present study analyzes the impact of various lubricant-cooling process agents on the durability of drill bits made of AISI M2 (DIN 1.3343) high-speed steel. The research was conducted for a wide range of steels and alloys, namely: 1045, 321H, Mo-PM (molybdenum powder alloy), and W-Ni pseudo-alloy. New lubricant-cooling process agents with diamond graphite submicropowder additive are studied. The optimal composition of diamond graphite additive is revealed when drilling these steels and alloys. Experimental studies established a positive effect of lubricant-cooling process agents with the diamond graphite submicropowder additive on the durability of the drill bits made of AISI M2 steel.

Enhanced surface properties of M2 steel by plasma nitriding pre-treatment and magnetron sputtered TiN coating

AISI M2 high-speed steels are widely used in cutting/forming tools due to their easy machinability and balanced toughness. Unfortunately, they exhibit severe cutting edge wear, which reduces their useful lifetime. The lifetime of such steels can be improved by titanium nitride hard coating. However, in sliding wear applications having a metal-to-metal contact, such coatings exhibit low adhesion to the substrate due to substantial hardness differences among coating and substrate. Here, plasma nitriding is performed before the deposition of magnetron sputtered-TiN coating using various nitriding parameters to find whether the surface properties of the duplex treated sample can be altered by changing these parameters or not. It is found that the surface hardness and hardening depth can be improved by using the duplex treatment as compared to only TiN coating. A significant decrease in wear rate is attained using the duplex treatment and substantial improvement by altering the plasma nitriding parameters.

Enhanced surface properties of M2 steel by plasma nitriding pre-treatment and magnetron sputtered TiN coating

AISI M2 high-speed steels are widely used in cutting/forming tools due to their easy machinability and balanced toughness. Unfortunately, they exhibit severe cutting edge wear, which reduces their useful lifetime. The lifetime of such steels can be improved by titanium nitride hard coating. However, in sliding wear applications having a metal-to-metal contact, such coatings exhibit low adhesion to the substrate due to substantial hardness differences among coating and substrate. Here, plasma nitriding is performed before the deposition of magnetron sputtered-TiN coating using various nitriding parameters to find whether the surface properties of the duplex treated sample can be altered by changing these parameters or not. It is found that the surface hardness and hardening depth can be improved by using the duplex treatment as compared to only TiN coating. A significant decrease in wear rate is attained using the duplex treatment and substantial improvement by altering the plasma nitriding parameters.

Cutting tools hardening and sharpening by fast argon and nitrogen atoms

A reamer made of AISI M2 high-speed steel was heated by ions accelerated from the plasma by a bias voltage applied to it and kept at 500°C for 120 min. Microhardness of the reamer surface increased by 1.75 times and the nitride layer thickness reached 130 μm. Nevertheless, radii of the cutting edges increased by 5 times up to ~ 40 μm, which made the tool blunt. Another reamer was heated by a converging beam of fast atoms produced by an immersed in the same plasma concave grid under a negative voltage of 5 kV. Due to uniform removal of the reamer material by the beam, the radii of cutting edges decreased from the initial value ~ 8 μm down to ~ 6 μm.

Strengthening of cutting tools using beams of fast neutral atoms in a low-pressure gas discharge plasma

The surface of a 26-mm-diameter reamer made of AISI M2 high-speed steel has been nitrided in a low-pressure glow discharge plasma. Then a 3-μm-thick wear-resistant TiN coating has been magnetron sputtered on the hardened surface. After the combined processing the reamer’s cutting edges radii grew from the initial value of ∼8 μm up to ∼37 μm. The reason for the strengthened tool blunting is selective sputtering of the edges by heating ions accelerated from the plasma. Another reamer under nitriding was heated by a beam of fast atoms arriving at the tool surface from an immersed in the plasma concave grid negatively biased to 6 kV. Due to the uniform sputtering of the tool surface by the beam, the edges radii after nitriding and 3-μm-thick TiN coating deposition did not exceed the initial value.

The effect of a boride diffusion layer on the tribological properties of AISI M2 steel

AISI M2 high speed steel is commonly used as cutting tool in the machining process. Nevertheless, their useful life can be easily reduced by an eventual failure. In the last few years, thermochemical surface hardening process in which boron atoms diffuse into metals surface have been reported as an alternative to improve tribological properties. In the present work, a diffusional boron heat treatment was carried out at 950 °C by 6 h on AISI M2 steel sample. Scanning Electron Microscopy (SEM) and Micro-hardness testing was undertaken with the purpose to assess the diffusional boride microstructure and its effect on mechanical properties. On the other hand, tribological test was performed using a ball on disc tribometer tracking their friction coefficient and volume loss. Surface damage was analysed using stereomicroscopy and SEM. The boride diffusional layer achieved 50 µm with an increment of 7 times in the microhardness regarding to untreated sample and 4 times regarding to the adjacent zone to the boride layer. In addition, a reduction of the friction coefficient and better wear response was achieved as a result of boride heat treatment.

Structure and Tribological Properties of CrTiAlCN Coatings with Various Carbon Contents

Multi-component CrTiAlCN coatings with different carbon contents were deposited on AISI M2 high-speed steels using unbalanced magnetron sputtering via adjusting the C2H2 flow rates, and their microstructures and mechanical properties were characterized by using SEM, EDS, XRD, Vickers hardness tester and scratch tester, respectively. The tribological properties of CrTiAlCN coatings sliding against SUS440C high carbon martensitic balls were performed using ball-on-disk tribo-tester. The results showed that CrTiAlCN coatings were mainly comprised of (111) and (200) crystal orientation. The maximum hardness of coatings was 29.4 ± 1.5 GPa as the carbon content was 22.5 at.%. With an increase in the carbon content of coatings, the friction coefficients and wear rates of CrTiAlCN/SUS440C tribo-pairs were significantly reduced, and the wear mechanism of coatings changed from adhesive wear to abrasive wear.

Influence of Tempering Time on the Microstructure and Mechanical Properties of AISI M42 High-Speed Steel

AISI M42 high-speed steel is prone to fracture as a result of its brittle martensitic microstructure together with abundant carbides located at the grain boundaries. In this study, a series of property tests including hardness, impact toughness, and wear loss were performed to study the effect of tempering conditions on the mechanical properties of AISI M42 high-speed steel over holding time ranging from 1 to 20 hours. The effects of the tempering time on the characteristics and growth of carbides were also investigated. The results indicated that carbides in the experimental steels were obviously coarsened when the tempering time exceeded 4 hours. The dimension of the carbides increased, while the volume fraction decreased with the increasing tempering time, and the grain sizes were significantly augmented due to the reducing of small carbides. Moreover, the dislocation density decreased with the increasing tempering time, which led to the reducing of the yield stress of high-speed steel. An appropriate holding time (4 hours) resulted in fine-scale secondary carbides and a smaller grain size, which efficiently improved the impact toughness and wear resistance simultaneously. Nevertheless, a prolonged tempering time (> 4 hours) promoted the coarsening and coalescence of carbides, which were detrimental to the impact toughness and wear resistance. Consequently, the formation of fine-scale secondary carbides is the major influential factor to improve both the wear resistance and impact toughness.