AISI M2 Research Articles

Molecular dynamics simulation of the influence of nanocutting parameters on microstructure of AISI M2

Molecular dynamics simulation has become the main analysis method of ultra precision machining of various materials. In this research, molecular dynamics method was used to explore the influence of nanocutting parameters on amorphous atoms, atomic coordination numbers, atomic strain and dislocations of AISI M2 workpiece. LAMMPS was used to construct the molecular dynamics model for CBN tool cutting AISI M2. The polycrystalline model of the workpiece contained 12 grains and iron, chromium and tungsten atoms. The polycrystalline model of the tool contained 3 grains and boron and nitrogen atoms. Tersoff, EAM, Morse and L-J potential energy functions were used to characterize the interaction between atoms. The following results were obtained through 8 groups of simulation experiments: (1) Both cutting speed and cutting depth promoted the amorphous transformation of workpiece atoms. (2) Under the extrusion of the tool, atoms with high coordination numbers were produced in the contact area between the tool and the workpiece. (3) The cutting depth was positively correlated with the average strain of workpiece atoms. Large strain atoms mainly occurred in the cutting area and gradually extended into the workpiece. (4) 1/2 < 111> dislocation was the most common dislocation form in nanocutting. This research plays a rich role in molecular dynamics simulation of nanocutting polycrystalline alloys.

Influence of carrier gas flow rate and particle size of AISI M2 in the laser-directed energy deposition process

ABSTRACT Additive manufacturing (AM) is a rapid prototyping technology that offers many advantages over conventional manufacturing processes. However, to make the most of the AM advantages, some requirements need to be met, such as the adjustment of process parameters and quality of the feedstock. This work assessed the influence of carrier gas flow rate and particle size of AISI M2 in the laser-directed energy deposition process (L-DED). Different carrier gas flow rates were tested for two powders with particle size of 53–150 µm (larger range) and 20–53 µm (lower range). The variation of carrier gas flow rate and particle size was assessed in single lines and layers. The results show that increasing the carrier gas flow rate provides better powder convergence in the region where there is interaction with the laser beam and faster particle velocity. The lower range tends to have greater efficiency in the deposition of single lines and layers. Regarding geometric characteristics, the aspect ratio did not show a well-defined trend as a function of the carrier gas flow rate and particle size, however, the layer height tends to be greater for the lower range, while the dilution tends to be greater for the larger range.

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.

Effect of Temperature on the Structure and Tribological Properties of Ti, TiN and Ti/TiN Coatings Deposited by Cathodic Arc PVD

Monolayers of Ti and TiN coatings, as well as a Ti/TiN bilayer coating, were deposited on AISI M2 steel substrates using the PVD cathodic arc technique. The coatings had a thickness close to 5 μm and an average roughness between 98.6 and 110.1 μm due to the presence of microdroplets on the surface. The crystalline structure of the materials was analyzed using Grazing Incidence X-ray Diffraction (GIXRD) with an increase in temperature to study the dynamics of oxide formation. A phase composition study was conducted using the Rietveld refinement method. At the temperatures where critical growth of titanium oxides, both anatase and rutile, was observed, pin-on-disk tests were performed to study the tribological properties of the materials at high temperatures. It was determined that the oxidation temperature of Ti is around 450 °C, promoting the formation of a combination of anatase and rutile. However, the formation of rutile inhibits the formation of anatase, which is stable above 600 °C. In contrast, TiN showed an oxidation temperature of 550 °C, with an exclusive growth of the rutile phase. The Ti/TiN bilayer exhibited mixed behavior, with the initial growth of anatase promoted by Ti, followed by the formation of rutile. Oxidation and tribo-oxidation dominated the wear behavior of the surfaces, showing a transition from mechanisms related to abrasion at low and medium temperatures to a combination of abrasion and adhesion mechanisms at high temperatures (800 °C).

Preparation of asymmetrical cutting edge geometries on micro end mills using pressurized wet abrasive jet machining for hard micromachining of AISI M3:2

Cutting edge preparation is an established approach in the field of machining technology for optimizing the performance of cutting tools. However, the potential of asymmetric geometries has not yet been sufficiently utilized for filigree micromilling tools. In this regard, the study presents investigations on the adjustment of asymmetric microgeometries through the design of the pressurized air wet abrasive jet machining (PAWAJM). The study features results regarding the design of the preparation process as well as subsequent application tests in a hard micromilling process of the hardened high-speed steel AISI M3:2. The application tests focus on the effect of the conditioned cutting edge on the process forces and the surface quality as well as the tool life. The results show that asymmetrical microgeometries with small average cutting edge rounding and a form-factor of K > 1.2 can be achieved by PAWAJM. Machining tests revealed a potential reduction of the wear development and process forces for modified tools with low cutting edge rounding and asymmetrical microgeometry.

Residual stress variations in substrate (AISI D2) during directed energy deposition process of high-speed tool steel (AISI M4) powder

This study aims to observe the residual stress in a substrate and predict stress behavior during the laser deposition process (DED) using finite element analysis (FEA). The residual stress observed on the substrate surface indicated that stress variation during the deposition process increases with proximity to the deposition area, resulting in higher residual stress levels. Additionally, tensile residual stress tends to increase with the height of the deposition area. While variations in the deposition area size influenced the residual stress, consistent stress levels were observed at the same measurement points across different area sizes. The deposition process was simulated using FEA, which confirmed that stress behavior is influenced by melting and solidification cycles. The residual stress levels after cooling aligned well with those observed in actual experiments. Therefore, this study suggests that stress variations can be effectively predicted by simulating the deposition process prior to conducting actual experiments.

Enhancing Quality Control: Image-Based Quantification of Carbides and Defect Remediation in Binder Jetting Additive Manufacturing.

While binder jetting (BJ) additive manufacturing (AM) holds considerable promise for industrial applications, defects often compromise part quality. This study addresses these challenges by investigating binding mechanisms and analyzing common defects, proposing tailored solutions to mitigate them. Emphasizing defect identification for effective quality control in BJ-AM, this research offers strategies for in-process rectification and post-process evaluation to elevate part quality. It shows how to successfully process metallic parts with complex geometries while maintaining consistent material properties. Furthermore, the paper explores the microstructure of AISI M2 tool steel, utilizing advanced image processing techniques like digital image analysis and SEM images to evaluate carbide distribution. The results show that M2 tool steel has a high proportion of M6C carbides, with furnace-cooled samples ranging from ~2.4% to 7.1% and MC carbides from ~0.4% to 9.4%. M6C carbides ranged from ~2.6% to 3.8% in air-cooled samples, while water-cooled samples peaked at ~8.52%. Sintering conditions also affected shrinkage, with furnace-cooled samples showing the lowest rates (1.7 ± 0.4% to 5 ± 0.4%) and water-cooled samples showing the highest (2 ± 0.4% to 14.1 ± 0.4%). The study recommends real-time defect detection systems with autonomous corrective capabilities to improve the quality and performance of BJ-AM components.

A microstructural modification strategy to improve thermal conductivity of tool steels produced by laser powder bed fusion

Laser additive manufacturing is a promising technology for producing tools with complex geometry. The tools for hot working applications typically require high thermal conductivity to reduce thermal stresses. However, the relationship between thermal conductivity and the unique microstructure created by Laser Powder Bed Fusion (LPBF) is not yet fully understood.In this study, we investigated the thermal conductivity of AISI M50 in the as-built and different heat-treated conditions. As-built samples exhibited anisotropy and low thermal conductivity. The low thermal conductivity can be improved after heat treatments by modifying the microstructure. Moreover, the influence of each microstructural characteristic was interpreted. Thereby, a correlation between thermal conductivity and microstructure can be addressed. With this knowledge, we proposed a suitable heat treatment concept for improving the thermal conductivity of additively manufactured tool steels.

Pulsed-dc bias magnetron sputtered TiB2 ceramic coating

Titanium diboride, TiB2, is well known as a ceramic material with a hexagonal structure which presents various attractive properties, such as high hardness and excellent corrosion, thermal oxidation, and wear resistance. However, one drawback of TiB2 coatings is their poor adhesion to substrate materials due to high compressive residual stress after deposition. The present study aimed to assess whether a PVD-TiB2 coating with both high hardness and sufficiently good adhesion to the substrate and good wear properties can be developed by a closed-field unbalanced magnetron sputtering system using pulsed-dc biasing. The TiB2 coating deposited on AISI M2 steel substrates was characterized in terms of the structural, mechanical and tribological property. From the experimental results, it can be concluded that a closed-field unbalanced magnetron sputtering system using pulsed-dc biasing can be used to produce a TiB2 coating with sufficiently good adhesion (82 N), and high hardness (2300 HK0.01), and low friction (0.34) under given deposition conditions. The deposition conditions, particularly substrate biasing and rotation, which inhibited the formation of (001) orientation, played a role in the coating's lack of superhardness.

Cutting edge preparation of micro end mills by PVD-etching technology

Micromilling tools face significant challenges in achieving cutting edge preparation by mechanical processes due to their small size. To address these limitations, a new approach for cutting edge preparation of micro end mills by physical vapor deposition (PVD) etching technology is presented. By adapting the etching strategy, which is conventionally used as pre-treatment process for PVD technology to clean and condition the surface of cemented carbide substrate, cutting edges of micromilling tools were successfully modified. The high-energy process variation by Advanced Arc-Enhanced Glow Discharge (AEGD) offers the possibility of achieving high material removal rates on the tool surfaces and thereby altering the cutting edge geometry. Fundamental investigations on material removal as well as on the effects on surface topography, sub-surface properties, and coating adhesion of a subsequently applied PVD coating are performed. To influence the topography and the cutting edge geometry, the preparation time tp and bias voltage UB were selected. Subsequently, the machining performance of the modified tools is evaluated in a micromilling process of the hardened powder-metallurgical high-speed steel AISI M3:2 with a hardness of 62 ± 1 HRC. For this purpose, micro end mills of cemented carbide with a diameter of D = 1 mm were conditioned, achieving asymmetric geometric properties of cutting edges with varying average cutting edges rounding of S¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\overline S}$$\\end{document}= 5.8 … 14.8 µm and a form-factor of K = 2.0 … 2.7. Based on the application tests a positive influence on the process forces was found. Thus, an efficient approach to cutting edge preparation can be identified by specifically designing ion etching in the PVD coating process.

Cutting performance of TiAlN-based thin films in micromilling high-speed steel AISI M3:2

Micromilling high-speed steel offers high precision in shape and geometry. However, the service life greatly depends on the wear resistance of protective thin films. In comparison to TiAlN, TiAlSiN and TiAlTaN thin films offer enhanced wear resistance for difficult-to-machine materials. Employing a hybrid process that combines direct current magnetron sputtering (dcMS) and high power pulsed magnetron sputtering (HiPIMS) enhances the properties of these films. In cutting tests, it is demonstrated that TiAlSiN and TiAlTaN outperform TiAlN in micromilling of high-speed steel AISI M3:2. Notably, dcMS/HiPIMS-TiAlSiN stands out by having the lowest reduction in cutting forces combined with reduced wear.

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.

Dry Grinding by Means of Additively Manufactured Toric Grinding Pins

AbstractThe dry grinding process is challenging due to the induced thermal loads into the workpiece, which leads to a reduction of the workpiece quality. One approach to reduce the thermal loads is to adjust the grinding tool geometry by inserting a porous structure for dry grinding. This porous structure can be implemented, for example, by additively manufactured grinding tools. For this purpose, the suitability of additively manufactured vitrified cubic boron nitride grinding tools for dry grinding of tempered AISI M3:2 was investigated and compared with conventionally manufactured grinding tools to investigate the possibility of reducing the high temperatures and to verify the advantage of additively manufactured grinding tools. For this the resulting topographies and residuals stress states as well as wear of the grinding tools were analyzed. Additively manufactured grinding tools generated constant surface roughnesses of below 1 µm as well as contant compressive residual stress states. These results were attributed to a continuous self-sharpening of the grinding tools, which was shown qualitatively and quantitatively on the basis of the tool surfaces. Additively manufactured grinding tools with a porous structure thus have the potential to increase the possibilities of dry grinding.

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.

Influence of the heat treatment on the mechanical and tribological properties of cryogenically treated AISI M2 steel

Cryogenic treatments are known to increase the wear resistance and toughness of steel. However, the literature reports some contradictory results. This work aims to investigate and determine the optimum cryogenic parameters combined with cycles of quenching and tempering of AISI M2 tool steel to increase wear resistance and toughness. Charpy specimens were austenitized (1185 °C, 1200 °C or 1215 °C), quenched to room temperature, cryogenically treated to −196 °C (20 h or 28 h), and subjected to double tempering (520 °C, 535 °C or 550 °C). A Taguchi L9 DoE approach was used to determine the optimum set of heat treatment cycles. Mechanical and tribological properties were investigated in terms of wear, impact, hardness, and microhardness tests. The results show that austenitization temperature (AT), tempering temperature (TT), and cryogenic treatment (CT) time are interdependent. Depending on the AT and TT parameters used, CT can improve, have little influence, or even deteriorate the mechanical and tribological properties of AISI M2 steel. The amount of retained austenite after CT ranged from 4.3 to 7.6%. Cryogenic treatment improves wear resistance and impact toughness simultaneously.

Rolling contact fatigue performance of M50 steel: A combined experimental and analytical approach to determine life

This article presents an experimental and analytical investigation into the rolling contact fatigue (RCF) performance of AISI M50 bearing steel across a range of Hertzian contact pressures (Ph=2.6GPa to 3.4GPa). RCF experiments were conducted using a ball-on-rod test rig at three contact pressures to experimentally establish the relationship between contact pressure (contact stress) and the RCF life of M50. Simultaneously, a previously developed continuum damage mechanics finite element (CDM-FE) model, employing the Fatemi-Socie critical plane approach as the failure criteria, was utilized to provide analytical predictions of RCF life. The CDM-FE model’s damage rate equation was calibrated using open literature AISI M50 bearing steel torsion stress life (SN) data. The CDM-FE model incorporated Voronoi tessellations to represent the material microstructure and capture the material topological effect on fatigue scatter. RCF simulations were conducted at seven contact pressures ranging from 1.0 GPa to 3.4 GPa in 0.4 GPa increments. Similar to the experimental results, the analytical RCF life data set yielded a relationship between contact pressure and simulation life for M50. Good corroboration is observed between the contact pressure – life relationships from the experimental and analytical RCF life data sets. This is significant as it supports the use of a hybrid approach combining experimental tools (e.g. torsion fatigue and ball-on-rod) and a CDM-FE computational model to efficiently assess the RCF performance of bearing materials.

Optimizing laser power of directed energy deposition process for homogeneous AISI M4 steel microstructure

Optimizing laser power of directed energy deposition process for homogeneous AISI M4 steel microstructure

Tribological Evaluation of Boride Layers Formed on an AISI M2 Steel Substrate by the Powder Packing Method.

Tribological Evaluation of Boride Layers Formed on an AISI M2 Steel Substrate by the Powder Packing Method.