AISI M2 Steel Research Articles

Multidimensional optimization of electrical discharge machining for high speed steel (AISI M2) using Taguchi-fuzzy approach

Electrical discharge machining (EDM) is one of the non-traditional machining processes characterized by its ability to machine parts that electrically conductive but difficult to be machined in the traditional machining processes due to its high hardness, complex geometry, and low tolerances. To minimize EDM process cost, ensure the highest process efficiency and achieve the highest product quality, the EDM process needs to be optimized. The aim of this research is optimizing EDM process parameters for machining HSS (AISI M2) material by use of copper electrode and brass electrode considering conflicting performance measures in one and multidimensional levels. The performance measures used in the current research are material removal rate (MRR) and electrode wear rate (EWR), while machining parameters that will subject to optimization process are current (A), pulse on (TON), and pulse off (TOFF). During optimization stages, the Taguchi method, signal to noise ratio (S/N ratio), and analysis of variances (ANOVA) will be used in the first stage to find the optimal machining parameters for each performance measure and for each electrode material. In the second stage, multidimensional optimization approach encompasses using the calculated S/N ratio as input from the first stage, fuzzy logic and ANOVA to calculate multi response performance index which will be used to select optimal machining parameters for each electrode and then select the best electrode and optimal machining parameters for machining AISI M2 steel. In one-dimensional optimization, for brass electrode, to maximize MRR value, the optimal machining parameters combination is A3TON1TOFF3 and to minimize EWR value, the optimal machining parameters combination is A1TON1TOFF2. For copper electrode, to maximize MRR value, the optimal machining parameters combination is A1TON1TOFF3 and to minimize EWR value, the optimal machining parameters combination is A1TON3TOFF1. In multidimensional optimization, for the copper electrode, the optimal machining parameters combination was A1TON1TOFF3 and for the brass electrode, the optimal machining parameters combination is A3TON1TOFF3. It could be concluded that EDM machining of HSS (AISI M2) by using the copper electrode will give the best results and the optimal machining parameters combination is A1TON1TOFF3. Yet, further research needs to be conducted to study these results and analyze machining process effectiveness in terms of cost and process sustainability, i.e. environmental impact. This research has both theoretical and practical implications.

Process parameters optimization of AISI M2 steel in EDM using Taguchi based TOPSIS and GRA

An attempt has been made to determine the suitable parameters that will give best quality product, on the basis of experimental data on the electric discharge machining (EDM) of AISI M2 steel with help of tungsten–thorium electrode as the EDM tool and compared the result based on different optimization techniques. In this study, Taguchi method along with TOPSIS & GRA has been applied to examine the capability of optimizing output performance characteristics for AISI M2 steel. The impact of input parameters (e.g. working current (IP), pulse on time (Ton) & spark gap (Sg)) on output parameters (e.g. MRR, EWR & SR) has been examined. To determine the most significant parameters analysis of variance (ANOVA) & F-test have been used at a 95% confidence interval by the application of MINITAB. Confirmatory tests validates the estimated results which show a correction of 0.037342 & 0.204935 in the preference values utilizing TOPSIS & GRA respectively.

Boriding Kinetics of FeB and Fe2B Layers on AISI M2 Steel by the Integral Diffusion Model

Boriding Kinetics of FeB and Fe2B Layers on AISI M2 Steel by the Integral Diffusion Model

A Microstructure Obtained on AISI 1018 and AISI M2 Steel by Powder Paste Pack Boriding Process

A Microstructure Obtained on AISI 1018 and AISI M2 Steel by Powder Paste Pack Boriding Process

TiN and Boride Layers Obtained by Dehydrated Paste-Pack Boriding and PVD Treatments Formed on AISI M2 Steel

TiN and Boride Layers Obtained by Dehydrated Paste-Pack Boriding and PVD Treatments Formed on AISI M2 Steel

Comparison of the Microstructure of M2 Steel Fabricated by Continuous Casting and with a Sand Mould

AISI M2 steel was smelted in a 150 kg medium-frequency induction furnace and cast to form round billets with a cross-section diameter of 100 mm via a vertical continuous caster and sand mold. The secondary dendrite arm spacing (λ2), cooling rates, permeability and size and distribution of grains and network carbides of the two billets were studied. The results show that the continuous casting process can effectively decrease the λ2 value, permeability and size of the grains and carbides and improve the distribution of the grains and carbides during solidification. The λ2 values of the billets cast with a sand mold and continuous caster are 37.34 μm and 21.14 μm, respectively, and the cooling rate is 3.6 K·s−1 and 12.0 K·s−1, respectively. The area fractions of carbides at the center of the billets cast with the sand mold and continuous caster are 0.24 and 0.16, respectively, and increase by 27.7% and 25.4%, respectively, compared with their average values. The average grain size of billets cast with the sand mold and continuous caster is 69.4 μm and 50.5 μm, respectively. Compared with the sand mold billet, the grain size at the center of the continuous casting billet is reduced by 25.5%. The relationship between the grain size and cooling rate is presented in this paper.

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.

Wear behavior of TC11 and AISI M2 in pin–disk tribo-system

The wear behavior and mechanism of TC11 (pins) and AISI M2 (disks) under different test conditions were studied. The results show that tribo-layers formed on the worn surfaces of both TC11 alloy and AISI M2 steel. As for TC11 alloys at 25 °C, the wear rate increased to high values with an increase in the load; and abrasive wear and adhesive wear prevailed. However, at 600 °C, the wear rate decreased sharply and oxidative wear prevailed. As for AISI M2 steels, at 25 and 600 °C, the wear rates were relatively low. The wear mechanisms at 25 and 600 °C were abrasive wear and oxidative wear, respectively. The wear rates of AISI M2 steel were lower than those of TC11 alloy at 25 and 600 °C. The wear performance of the tribo-pair was noticed to be closely related to their mutual contact mode except for the test conditions and the pin and disk materials, and the intermittent contact mode reduced wear of AISI M2 steel.

Investigation of the Cutting Performance of Cutting Tools Coated With the Thermo-Reactive Diffusion (TRD) Technique

The life of cutting tools used in metal cutting operations is limited due to wear. Therefore, increasing wear resistance is of great importance for minimizing economic losses. By using different coating techniques, tools may be coated with harder compounds for enhancing wear resistance. Tool hardness and toughness are also increased through coating. In this study, boron and titanium coatings were applied on round cutting tool surfaces made of AISI D2 and AISI M2 steels by the thermo-reactive diffusion technique. AISI D2 cutting tool surface was coated with boron at 950 °C for 1 hour, and AISI M2 cutting tool surface was coated with boron at 1000 °C for 1 hour. After boron coating, the surfaces of the samples were coated with titanium at 1050 °C for 1 hour. The coated samples were characterized by using SEM, X-ray diffraction, EDS analysis, and micro hardness tests. Machining tests were performed to observe the wear resistance of the samples and the roughness of the machined surface. Machining tests were carried out on DIN 1651 free-cutting steel. Cylindrical turning tests were run at three different cutting speeds, 38, 73, and 138 m/min. and at three different feeding values, 0.08, 0.12, and 0.16 mm/rev. The results showed that the boron- and titanium-coated tools performed 50% better than the just boron-coated tools. In terms of surface roughness, it was determined that there was no significant difference between the coated and uncoated tools. The cutting performance values of our coating method were compared to those of ISCAR brand RCMT (code of the insert used in turning and milling operations in the ISO norm) inserts coated with the PVD and CVD methods, and it was seen in the experimental results that the tool coated with the TRD method performed better.

Cold forging tool for gear accuracy grade improvement by a different shrink fitting method

Abstract The manufacturing of the gear profile by Metal Forming is widely used in industry due to its quality and production capability. Direct cold extrusion has this characteristic and with support of peripheral technologies allows the development of asymmetric parts with complex geometry and near net shape. These resources, added with the great experience of a Brazilian forging company with strong presence in the cold forging market, allowed to develop a cold extrusion process to produce spur gears using the low carbon steel alloy described as SAE 10B22. The goal of this study was to develop the whole process, precision tooling project and manufacture as well as the experimental availability of the process. The tools were manufactured with high speed steel AISI M2 having a hardness in a range from 61 up to 63 HRc. The shrink rings were manufactured using steels with more toughness, such as S1 and H13. The application of shrink rings for the prestressing of tooling was evaluated using two different methods. The first one is using conventional shrink rings with tool steel, while the second is the stripwinding concept developed by the company STRECON.

Tribological performance of ternary TiMN films (M=AL, B, and Cr) deposited by cathodic arc on M2 steel

AbstractIn the industry, the titanium nitride (TiN) coating is widely used in cutting tools, decorative and corrosion protection film, but unfortunately, this coating presented a poor performance under some work condition. For that, different studies have been dedicated to improving its properties with the inclusion of a third element that modifies the film structure, chemical and mechanical properties. In this work, TiN layers with/without of Al, B, and Cr inclusion were studied in order to analyze their effect in the film tribological performance. These were deposited using cathodic arc PVD technic on AISI-M2 steel. They were chemical and structural characterized using EDX and XRD, respectively. While the film thickness was determinate using a ball-cratering technique. Their tribological performance was studied using a sliding reciprocating movement in dry conditions, under three loads, at 30 min against Al2O3 ball as counterbody. The resulting wear tracks were studied using optical microscopy in order to study the wear mechanism. Raman spectroscopy was used to determinate the chemical changes produced on wear zones and the lost material was measured with a stylus profilometer. As result, the structure and morphology were modified with the inclusion of the third element. The TiN with the inclusion of Al and B presented a higher friction force and wear rate than TiN films. While the TiN with Cr inclusion film presented the best tribological performance with lower wear rate and friction coefficient. The Raman studies did not showed considerable changes on the damage coted surface areas, except for TiAlN coating that show the M2 tool steel Raman spectra on the areas where the film was removed.

Microstructure, mechanical and tribological properties of TiBC coatings by DC magnetron sputtering onto AISI M2 steel using independent TiB2 and graphite targets

Despite TiB2 being a ceramic material widely known for its high hardness, chemical resistance and high thermal stability; its use in coatings for industrial conditions has been limited due to low adhesion, which is associated with high residual stresses. Recently, several investigations have shown that the incorporation of carbon within TiB2 coatings reduces residual stresses and increases adhesion, making Ti-B-C coatings excellent candidates for applications at high temperatures. In this research, DC UBMS Ti-B-C coatings were deposited onto AISI M2 steel substrates. The power density of TiB2 was fixed at 2.4W/cm2 and four different graphite power densities were made in order to obtain four different power ratios (WC/WTiB2) and carbon content in the Ti-B-C coatings. XRD and AFM results suggest the formation of nanocomposite coatings, with TiB2 nanocrystals embedded in an amorphous carbon matrix. SEM images revealed a glass-like structure for coatings with a low power ratio, which became a dense and featureless-like structure with a higher power ratio. A progressive decrease in hardness and Young's modulus was observed with the increase in carbon content. Hardness up to 27GPa was reached with lower carbon content and decreasing under 5GPa with the higher carbon content. The Young's modulus exhibited the same feature. Tribological properties of the coatings were investigated using a pin-on-disk tribometer. All coatings showed μ higher than the AISI M2 substrate, and only the coatings with a power ratio of 1.30 showed μ over 0.30. Regarding the wear rate, it remained almost constant for all the Ti-B-C coatings.

Sliding wear of borided sintered AISI M2 steel coated with AlTiN/CrN multilayer

In this work, the effect of the combination of solid boriding treatment on High Speed Steel AISI M2 produced by conventional powder metallurgy (P/M) and AlTiN/CrN film deposition by cathodic arc PVD process is evaluated in terms of the ability to withstand load during sliding wear tests and in terms of adhesion of the multilayer film. The wear resistance of the compound was evaluated by pin-on-disc sliding tests using variable speeds (0.1 m/s and 0.3 m/s) and alumina counter-body diameters (3 mm and 6 mm). The boriding treatment in AISI M2 steel promoted the formation of FeB and Fe2B layers. The average hardness of the borided layer (2162 HV0.025) was approximately 2 times greater than the hardness of quenched and tempered AISI M2 steel (945 HV0.025). The average hardness of the multilayer film was 3912 ± 504.76 HV0.025. The Borided + Film (BF) samples presented higher dry sliding wear resistance in all test conditions. For BF samples, wear on the counter-body was greater and the material removed from the counter-body formed a transfer layer onto the track, resulting in negative wear volume for some test conditions. The boriding treatment improved resistance to plastic deformation in both Borided (B) and Borided + Film (BF) conditions.

Effect of amorphous silicon interlayer on the adherence of amorphous hydrogenated carbon coatings deposited on several metallic surfaces

The effect of an amorphous hydrogenated silicon (a-Si:H) interlayer on the adherence of amorphous hydrogenated carbon (a-C:H) coatings deposited on four metallic surfaces: AISI M2 steel, AISI 304 stainless steel, Nitinol alloy, and Ti6Al4V alloy was studied. The interlayers and the coatings were deposited employing an asymmetrical bipolar pulsed-DC PECVD system with an active screen. Multilayer a-C:H coatings were also deposited, with the aim of obtaining thicker films. The interlayers were synthetized by varying the applied negative pulse amplitude from −0.8 kV to −10 kV, keeping their thickness constant at 250 nm. The coatings' adhesion was evaluated using classical scratch and VDI 3198 indentation tests. Raman spectroscopy was used to analyze the films' atomic arrangements. The total compressive stress was determined through the measurement of the substrate curvature before and after the film deposition, while nanoindentation experiments allowed determining the films' hardness and elastic modulus. In order to determine the chemical bonding between a-Si:H and the metallic surfaces, X-ray photoelectron spectroscopy (XPS) was used. The obtained results showed high values of critical loads, allowing a high degree of adherence of the a-C:H coatings to all the metallic materials. The highest Lc1 critical load values (≥25 N) were determined when the a-Si:H interlayers were deposited using the highest negative applied voltage (from −6 kV to −10 kV) on the Nitinol alloy surfaces. The XPS results suggested that the high degree of adhesion of the a-C:H coatings to Nitinol could be attributed to chemical bonds of TiSi and NiSi formed in the interface, while for the Ti6Al4V alloy the TiSi bonds predominated. On the other hand, on steel surfaces the adhesion was due to FeSi bonds. A combination of a modified pulsed-DC PECVD system with an active screen and an a-Si:H interlayer allowed depositing hard, adherent, and low-stress a-C:H coatings.

Study of dry sliding wear characteristics of stellite 6B versus AISI M2 steel at various sliding velocities

The wear performance of Stellite 6B versus AISI M2 steel in dry sliding at various sliding velocities (from 0.95 to 4.71 m/s) were systematically studied by pin-on-disc wear test and analysis of debris, tribo-layers and worn surfaces of both pin and disc. The mechanical performance of pin and disc were also studied by hot hardness test. The results showed that Stellite 6B underwent a severe-to-mild wear transition with the increase of sliding velocity in the Stellite 6B alloy/steel tribo-system. The temperature at worn surface increased with the increase of velocity and load, leading to the oxidation of the worn surface and the variation of mechanical strength of pin and disc. It was the surface state rather than the variation of the mechanical strength that impacted the wear transition. The critical transition sliding velocity for the Stellite 6B alloys was 2.51 m/s, which divided the sliding velocities into two regions. When the velocity was among 0.95–2.51 m/s, the wear mechanism turn from abrasive and delamination wear to adhesive wear gradually, resulting in the decrease of wear rate. While in the region that the sliding velocity was above 2.51 m/s, oxidative wear prevailed and the wear rate decreased due to the formation of mechanically mixed layer (MML).

Adhesive and Cohesive Strength in FeB/Fe2B Systems

In this work, FeB/Fe2B systems were evaluated by the scratch test. The powder-pack boriding process was performed on the surface of AISI M2 steel. The mechanical parameters, such as yield stress and Young’s modulus of the boride layer, were obtained by the instrumented indentation technique. Residual stresses produced on the boride layer were estimated by using the x-ray diffraction (XRD) technique. The scratch test was performed in order to evaluate the cohesive/adhesive strength of the FeB/Fe2B coating. In addition, a numerical evaluation of the scratch test on boride layers was performed by the finite element method. Maximum principal stresses were related to the failure mechanisms observed by the experimental scratch test. Shear stresses at the interfaces of the FeB/Fe2B/substrate system were also evaluated. Finally, the results obtained provide essential information about the effect of the layer thickness, the residual stresses, and the resilience modulus on the cohesive/adhesive strength in FeB/Fe2B systems.

Micro-abrasive wear mechanisms of P/M AISI M2 steel with different surface treatments

Boriding, heat treatment (quenching and tempering) and PVD (Physical Vapor Deposition) film deposition were applied to P/M (Powder Metallurgy) AISI M2 steel. Four sample conditions were produced: Quenched and tempered AISI M2 (QT), Borided AISI M2 (B), Quenched and tempered AISI M2+Film (QTF) and Borided AISI M2+Film (BF). The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and the Vickers microhardness test. The load applied in the micro-abrasion tests (fixed-ball) was 0.49N and abrasive slurry concentration was 0.1g/cm3. Silicon dioxide (SiO2) abrasive powders (approximately 80% of particles between 1 and 5μm) were used in the abrasion experiments. Wear coefficient and mechanisms of all conditions were compared. The XRD analysis revealed the presence of a biphasic layer of borides (FeB and Fe2B phases) on the borided samples. The film thickness was 2.1±0.4μm and the hardness of the multilayered AlTiN/CrN film was about 3912HV0.025. The borided layer thickness was 46.5±5.1μm and the hardness average of 2162HV0.025. The wear mechanism for the QT and QTF samples was two-body abrasion (grooving abrasion). There was a reduction on the signs of grooving abrasion for the B and BF samples due to the increase in plastic deformation resistance.

A microstructural analysis of aluminum buildup during thermomechanical processing

The microstructure and composition of a roll coating built-up on an AISI M2 steel work roll during a 20 pass hot rolling schedule using a laboratory rolling tribo-simulator with a roll-on-block configuration was examined. The AISI M2 steel work roll was characterized by grinding grooves and possessed a surface roughness (Ra) of 0.17μm. The roll coating developed under these lubricated conditions was discontinuous, patchy and streaked out in the rolling direction. The microstructure and chemical composition of the material transfer that made up the roll coating was analysed and revealed to possess a complex composite microstructure consisting of nanocrystalline aluminum, nanocrystalline/amorphous MgO and amorphous carbon layers. The nanocrystalline MgO layers were porous structures lying between the solid metallic aluminum layers. Debris particles from the wear of the work roll were detected embedded within the carbon layer and at the base of the roll coating. The microstructure of the roll coating appear to be determined by the deformation conditions experienced during the rolling process, while its composition is dependent on the composition of the rolled alloy, the work roll and the lubrication conditions employed.

Tribological coatings for improving cutting tool performance

With an increasing usage of advanced high-strength steels, there is an escalating need for improvements in cutting tool performance for these alloys. In this study, the tribological performances of Cr2N, WC/a-C:H, and Ti-MoS2 coatings on AISI M2 steel were examined. Surface treatments were evaluated using dry pin-on-disk testing, Charpy impact testing, and a reciprocating impact-sliding test rig (RISTR) designed to replicate the interaction between cutting tools and high-strength steel sheet. Charpy testing of coated specimens showed no statistical change in impact toughness from the untreated steel. Pin-on-disk testing was performed to quantify the friction and wear of untreated and coated tool steel. These tests showed that Ti-MoS2 coated tool steel had the lowest friction coefficient, and Cr2N, the lowest wear rate. Impact tribometer testing showed that the Ti-MoS2 coating yielded an increase of 370% in the number of cycles to failure over untreated specimens, while the WC/a-C:H coating was found to decrease the number of cycles to failure over untreated specimens. With an impact stress lower than the compressive yield strength of the AISI M2 steel, the fatigue life of the surface treatments scaled approximately as E2/H3, the inverse of the resistance to plastic deformation.

Wear performance of different nitride-based coatings on plasma nitrided AISI M2 tool steel in dry and lubricated conditions

AISI M2 high speed tool steel is one of the widely used materials in the machining industry. The most common problems of this material are wearing of the cutting edge and adhesion of the work materials to the tool during the machining operations. To overcome these disadvantages, single and duplex surface treatments combining a diffusion process and a thin film ceramic coating are performed. In this study, various nitride-based coatings (TiN, TiCN, AlTiN and CrN) were deposited on untreated and plasma nitrided AISI M2 high speed tool steel specimens using cathodic arc physical vapour deposition (CAPVD) technique. The plasma nitriding treatment was performed in 50%N2−50%H2 gas mixture at 500°C for 2h. The influences of different surface treatments on structural properties of AISI M2 steel were investigated by means of field emission scanning electron microscope, X-ray diffractometer, focused ion beam milling system, microhardness tester and optical profilometer. The tribological properties of specimens were examined in dry and cutting fluid conditions by using reciprocating sliding wear test with Al2O3 ball as a counter material. According to tribological test results, the solely coating treatment was more effective in improvement of the wear resistance of AISI M2 high-speed tool steel rather than duplex treatment. The lowest worn volume was obtained from the solely CrN coated surface. Whereas under cutting fluid condition, solely TiN and TiCN coated surfaces showed higher wear resistance. It was also observed that the friction coefficients of all specimens tested in boron-containing cutting fluid were lower and quite stable compared with dry sliding condition.