M2 Tool Steel Research Articles

Effects of process parameters on the performance of electrical discharge machining of AISI M42 high speed tool steel alloy

High strength temperature resistant alloys used in sophisticated applications in the industries are hard to machine owning to their high strength and improved mechanical properties. They are preferably machined by non-conventional machining methods due to their better control and automation. Among these non-conventional machining methods Electrical discharge machining (EDM) is one of the versatile machining process used by the manufacturing and automotive industries. In this study, such alloy AISI M42 tool steel used in aero-space and thermal applications is machined with EDM. The effect of specific machining parameters on MRR (Metal Removal Rate) was investigated during machining.During EDM commercial grade EDM-50 oil was used as di-electric fluid in this study.The present study reveals that maximum MRR was observed at -ve tool polarity. The most influential parameter effecting this process was found to be tool polarity followed by current.

EFFECT OF RAPID COOLING FROM THE SEMISOLID OR LIQUID RANGE ON STRUCTURE AND PROPERTIES OF M2 TOOL STEEL

M2 tool steel was used as a feedstock material for casting from the the semisolid range between 1310-1350oC corresponding to 25 - 50 % of the liquid phase. The chemical composition of the investigated steel is following: 0.85%C, 3.9 %Cr, 6.7 %W, 4.7 %Mo and 1.7 % V. A specially constructed machine allowed thixoforming in a protective argon atmosphere and semisolid forming at a high piston velocity powered by a high air pressure. After heating of the feedstock using induction heating by the stamping of semi-liquid sample to a graphite mould pre-heated by resistance heating. The material after thixoforming from 1315oC shows a globular microstructure with a relatively small globule’s size between 30-50 μm. The crystal structure of globules contained, austenite and martensite, while that of the eutectic, ferrite and W2C, Fe3C, Mo2C, M23C6 and VC carbides as determined by X-ray studies and confirmed using electron diffraction studies. The alloying elements like Mo, W and V are concentrated in the eutectic, while Cr only in thixoformed samples segregates to the carbides and indeed M23C6 was identified. The hardness significantly increases up to 780 HV after thixo-forming due to formation of martensite. The other part was cast from the liquid phase at 1450o C using melt spinning method allowing high cooling rate. The microstructure of melt spun ribbon shows a cellular microstructure of austenitic and martensitic structure without the eutectic. The WC and M23C6 carbides were located at the cell’s boundariers. The microhardness near 1300 HV of the ribbon was much higher than that of semisolid formed samples.

Experimental Investigation to Minimize Resultant Vibration Signal in CNC Turing Operation of Hard AISI M2 Tool Steel

Experimental Investigation to Minimize Resultant Vibration Signal in CNC Turing Operation of Hard AISI M2 Tool Steel

Influence of substrate bias on microstructural evolution and mechanical properties of TiAlSiN thin films deposited by pulsed-DC magnetron sputtering

Substrate bias is one of the many factors, influencing the microstructure and, thus, properties of physical vapor deposition coatings. The aim of this study is to investigate the effect of varying substrate bias on the microstructure and mechanical properties of TiAlSiN coatings deposited on M42 tool steel substrates at 500°C by a pulsed-DC close-field unbalanced magnetron sputtering system (CFUBMS). The microstructure of the as-deposited coatings was characterized by a range of techniques, including transmission electron microscopy, glancing angle X-ray diffraction and X-ray photoelectron spectroscopy. In addition, nanoindentation measurements were conducted to evaluate the mechanical properties of these coatings. It was found that an increase in substrate bias imposed minimal effects on the composition of the as-deposited TiAlSiN coatings, but had a significant influence on both the phase composition and microstructure of the coatings. As the substrate bias voltage increased from −40 to −80V, a transition from zone-2 type structure to zone-3 type structure was observed, together with a reduction of the width of columnar grain from ~180 to ~60nm. There was also a structural transition from a mixed fcc TiN+fcc AlN phases into a single fcc TiAlN phase as the negative substrate bias was increased above 60V. Hardness and modulus were observed to increase with increasing bias voltage. Solid solution hardening and Hall-Petch effects are believed to be responsible for the hardness improvement.

Noncontact measurements of acoustic emissions from the single-point turning process

Single-point turning is a fabrication process that is fundamental to manufacturing, comprising a significant portion of value-added operations. Vibration at the tool/workpiece interface affects surface finish, residual stress, and chemical reactivity of machined components. This phenomenon also affects tool life and therefore production cost. The study and measurement of this phenomenon has traditionally been done using a transducer in contact with the cutting tool or is in line with the cutting tool/tool holder assembly. While this setup has been acceptable for laboratory studies, implementation on actual production platforms has not been widespread, with open loop machine tool parameter control still being the norm. The goal of this study involves the use of a noncontact transducer (microphone) to gauge detectability and measurability of machine tool vibration attributable to the single-point turning process performed on a manual lathe situated in a shop floor environment. Such measures as characterization of the frequency content transmitted and the sound pressure level measured while machining a group of materials of interest are quantified and discussed. The results of the work show that the acoustic energy attributable to single-point turning is detectable using the noncontacting sensor, producing energy mostly in the ultrasonic (f > 20 kHz) range. Individual materials of interest (M42 tool steel, tungsten tantalum alloy, aluminum 6061, and Nitronic 33 stainless steel) are shown to emit distinct frequency signatures when excited using identical process parameters. Potential sources of ultrasonic acoustic emission are postulated and discussed, along with control of the turning process using the acoustic signal as an input and selected process parameter changes as the output.

Sintering of AISI M2 Tool Steel Processed in High-Energy Planetary Mill

This work aimed to evaluate the effect of pre-sintering annealing heat treatments and sintering times in AISI M2 high-speed steel powders processed by high energy milling. Turning chips were obtained from an AISI M2 drill bit that was annealed during 2 hours at 900°C, under argon atmosphere, before machining. Subsequently, the chips were milled during 10 hours in a high energy planetary mill with a power ratio of 10:1, also under argon atmosphere. Half of the powder mass was annealed at 650oC during 30 minutes under argon atmosphere after milling. Three different samples were prepared, consisting of: non-annealed powder, annealed powder and a mixture 1:1 of annealed and non-annealed powders. All powders were compacted by uniaxial pressing before sintered. Compressibility curves were obtained for all samples. Sintering process was conducted at 1200°C during 1, 2 and 3 hours and samples were cooled inside the furnace. The annealed powder sample presented the best compactation behavior, due to its restored ductility, followed by the 1:1 mixture of annealed and non-annealed powders. The microstructure of sintered samples displayed a ferritic matrix surrounded by carbide networks at grain boundaries. Higher sintering times resulted in carbon impoverishing, leading to lower volume fractions of carbides and hence reducing its hardness. Non-annealed powders showed higher dependency of sintering time to reduce their porosity. The best results were obtained for the annealed powder with shorter sintering time, since it presented low volume fraction of porosities and smaller grain sizes.

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.

Unproblematic Technique for EDMing of M2 Tool Steel with Unlike Electrodes for Licking the Multi Response Trouble

Objectives: To solve the multi-response trouble with the influence of process parametric quantities of the electric discharge machining (EDM) on M2 tool steel with unlike electrodes for maximum material removal rate (MRR) and minimum tool wear rate (TWR), surface roughness (SR). Methods/Statistical Analysis: Taguchi mixed DOE was used to determine the optimal setting for prime response and further transformed it into signal-to-noise (S/N) ratio and weighted with the most prominent S/N ratio of optimal level for each factor. It was found after conformation examination that the best results of responses were with powder metallurgy copper-titanium tool at straight polarity in average addition of aluminium powder during PMEDM at minimum current, duty cycle values and maximum value of gap voltage. The weight loss method is used for the study. Findings: The restraint and effectuality of this approach shall make it hypnotic to practicians for licking the multi-response trouble in a broad range of this technique. Application/Improvements: It may further enforced to improve the veracity and effective to use in any field of engineering applications with petty computation.

Parameters Optimized Specifying for EDM with PM/Conventional Electrodes on M2 Tool Steel using Taguchi and TOPSIS

Objectives: The scope of this experimental work of electrical discharge machining (EDM) process with and without the addition of abrasive powder while executed on M2 tool steel for the advancement in surrounding safety factors to meliorate the surface quality. Methods/Statistical Analysis: Taguchi’s L36 mixed orthogonal array is used after identification of most appropriate six input parameters (polarity, electrode type, concentration of abrasive, discharge current, and gap voltage and duty cycle) for maximum MRR and minimum TWR, and SR. Findings: To recognize the significant factors ANOVA is used and TOPSIS determine the 10.47% overall improvement in all responses with the optimal level of process parameters after confirmatory test. Energy dispersive X-ray (EDS) and Scanning electron microscope (SEM) analysis applied to examine the surface quality. Application/Improvements: This study finds the downfall of titanium from powder metallurgy tool electrode (CuTi) and deposition of aluminium material from PMEDM may also be implemented to improve the method of computation and precision.

Determination of Film Thickness Through Simulation of Vickers Hardness Testing

In recent decades, changes in the surface properties of materials have been used to improve their tribology characteristics. However, this improvement depends on the process, treatment time and, essentially, the thickness of this surface film layer. Physical vapor deposition (PVD) has been used to increase the surface hardness of metallic materials. The aim of the present study was to propose a numerical-experimental method to assess the thickness (l) of films deposited by PVD. To reach this objective, Vickers experimental hardness data (HV) assays were combined with numerical simulation to study the behavior of this property as a function of maximum penetration depth of the indenter (hmax) into the film/substrate conjugate. A strategy was developed to combine the numerical results of the H x hmax/l curve with Vickers experimental hardness data (HV). This methodology was applied to a TiN-coated M2 tool steel conjugate. The mechanical properties of the studied materials were also determined. The thickness results calculated for this conjugate were compatible with their experimental data.

EFFECTS OF Mo CONTENT ON THE MICRO-STRUCTURE AND TRIBOLOGICAL PROPERTIES OF CrMoAlN FILMS

In recent decades, CrAlN coatings have been widely used for cutting tools due to their high hardness, good wear resistance, especially excellent thermal stability and oxidation resistance. However, the rapid development in high speeds and dry cutting applications demands further improvement in hardness and wear properties of CrAlN coatings. Mo nitrides coatings are commonly used as protective surface layers against wear and corrosion. The combination of CrAlN and Mo may lead to the development of new composite coatings with superior wear properties. In this study, the CrMoAlN multilayer coatings with different Mo contents were deposited on M2 tool steel and silicon wafers substrates by closedfield unbalanced magnetron sputtering ion plating (CFUMSIP) technique in a gas mixture of Ar+N2. The chemical composition, surface and cross sectional morphologies, microstructure, mechanical and tribological properties of coatings were studied by EDS, SEM, XRD, XPS, nano-indentation and pin-on-disk tribometer, respectively. The results indicate that the CrMoAlN coatings exhibit fcc structure. Mo atoms substitute Cr and/or Al atoms in CrAlN lattice forming the solid solution CrMoAlN coatings. The surface and cross-sectional morphologies of the CrMoAlN coatings show that the grain size and the column width decrease with the increasing of Mo content. Nano-indentation result reveals a promoted hardness and elastic modulus *浙江省自然科学基金资助项目Y15E050060 收到初稿日期: 2015-09-21,收到修改稿日期: 2016-03-09 作者简介:楼白杨,女, 1958年生,教授,博士 DOI: 10.11900/0412.1961.2015.00493 第727-733页 pp.727-733

Friction Behaviour of Multilayered Graphene against Steel

ABSTRACTFrictional behaviour of multilayered graphene was studied in air with different relative humidity (RH) levels (10–52% RH). Pin-on-disk type sliding tests were performed and the running-in and steady state coefficient of friction (COF) values were measured against M2 tool steel counterface. On increasing the RH, multilayered graphene showed a reduction in steady state COF from 0.11 at 10% RH to 0.08 at 52% RH. The low steady state COF values observed in graphene could be attributed to the transfer layer formed on the M2 tool steel counterface. A sliding-induced structural change was observed in graphene transfer layers which could have facilitated the graphitic transfer layer formation. The multilayered graphene showed a lower steady state COF values at all RH compared to non-hydrogenated diamond-like carbon (NH-DLC) which recorded a steady state COF of 0.47 at 10% RH and 0.25 at 52% RH.

Effect of Substrate Heat Treatment on Wear Behavior of Fe- and Ni-Based Hardfacings

In different fields of high abrasive processes, e.g. in agriculture and mining industry, components made of tempering steel are additionally protected with a wear resistant alloy on high loaded sections. An industrial standard process flow includes heat treatment of components after hardfacing process. However, the exact effect of heat treatment procedure on wear performance of hardfacings is still mostly unknown.The main aim of this study was to determine the influence of substrate heat treatment on iron and nickel based hardfacings under two and three-body conditions. Commonly used wear resistant tempered steel was used as substrate material. Heat treatment investigations were performed on two Fe-based tool steel alloys (M2 and FeVCrC) and a Ni-based alloy reinforced with WC/W2C (Ni-FTC) deposited by plasma transferred arc technology (PTA), respectively. After hardfacing a heat treatment optimized for tempered steel substrate was performed on hardfaced samples.Microstructure investigations were done by optical microscopy, scanning electron microscopy and hardness measurements. Additionally wear behavior was estimated by dry-sand rubber-wheel test (three-body abrasion) and continuous impact abrasion test (two-body abrasion).Results showed significant influence of heat treatment, due to microstructural changes, on wear performance under 3-body conditions of Fe-based tool steels. This effect was not as pronounced in Ni-based alloy than in types of tool steel. Interestingly, in both M2 tool steel and Ni-based systems heat treatment led to decrease 2-body wear resistance. However, heat treated V-rich tool steel type showed good wear performance in continuous impact abrasion test. Composed wear map, based on this study, shows critical changes in general wear performance for investigated hardfacings.

Tribological behavior of VC/Ni multilayer coatings prepared by non-reactive magnetron sputtering

Ceramic–metal multilayer coatings generally exhibit considerably enhanced wear resistance, due to an attractive combination of metal and ceramic phases. In this work, VC/Ni multilayer coatings were prepared with non-reactive magnetron sputtering. Tribological behavior of the coatings was investigated by ball-on-plate dry sliding tests, followed by in-depth microscopic examination of the worn surfaces. The VC/Ni multilayer coatings exhibited the wear rates of 10−15m3/N m that was lowered by one order of magnitude in comparison with M2 tool steel. The results revealed that the wear process of coatings was influenced by the modulation period, and might further indicate that a sufficient thickness of hard layers was required to enhance the deformation resistance for optimizing the wear resistance of ceramic–metal multilayer coatings.

Wear Behaviour of Cryogenic Treated M2 Tool Steel under Dry Sliding Condition

The technique of cryogenic treatment of cutting tools is an inexpensive permanent treatment process that improves the physical and mechanical properties of materials such as metals, plastics and composites. It promotes the transformation of the retained austenite into martensite at cryogenic temperatures and also facilitates the formation of fine carbides in the martensite, thereby improving the wear resistance.This paper compares the wear behaviour of hardened and triple tempered AISI M2 high-speed steel and the same steel that was hardened and triple tempered in conjunction with a deep-cryogenic treatment at 88K for 16 and 24 hours. Test materials were subjected to wear tests on pin-on-disc machine in dry sliding condition. Equations are developed for predicting the wear resistance of M2 tool steel material. The hardness data wear loss and microstructure throw light on the improvement in wear resistance property of the M2 tool steel.It is demonstrated that the properties of the cryogenically treated samples are superior to those of conventionally treated. 24 hours cryogenically treated hardened and triple tempered M2 tool steel shows excellent wear resistance properties over 16 hours cryo-treated M2 and conventionally treated M2 tool steel material.

Simulation the flow of semi-solid steel alloy using an enhanced model

Simulating steel semi-solid metal forming close to a real industrial forming is necessary to reduce potential run-time errors and costs. Simulating requires modeling of semi-solid behaviour. In this work a model based on micromechanical analysis with consideration the viscoplastic response along with an enhanced Herschel-Bulkley model has been proposed to predict the flow behaviour of semi-solid M2 high speed steel. This model is introduced to overcome the limitations of the previously used models. The extracted model parameters from the steady state flow stress and step-change of shear rate experiments were then calculated and fitted to the experimental rheology results of continuous cooling. The model was then implemented linking into the computational fluid dynamics software (FLOW 3D Ver.9.3). A T-Shape die used to investigate the flow front of semisolid alloy. Also the extracted parameters at low shear rate in the step change experiments used for simulation of the compression process of M2 tool steel at high solid fraction by the proposed model and in the ABAQUS 6.9 software. The experimental results of compression test shows a well agreement with simulations results indicative of the performance of the proposed model to predict rheological properties and flow behaviour of semi-solid states especially for the tool steel systems in the wide range of liquid fraction.

Surface morphology and mechanical strength of AISI M2 tool steel treated in abnormal glow region of plasma

Plasma ion nitriding is a flexible and multi-functional casehardening technique used in the given study for surface modifications of AISI M2 tool steel (0.9% C, 4.2% Cr, 5.0% Mo, 6.0% W, and 2.0% V). By varying the plasma treatment time from 1 to 4 hour and the filling gas pressure from 1 to 4 mbar, the surface nitriding was carried out in the abnormal glow region of a pulsed DC discharge. Pre-plasma treatment heating of the samples was performed by a heating unit; the substrate temperature was raised to 500°C, with the ramping rate of 15°C. The resultant microscopic changes in the surface properties of the plasma treated tool steel were studied with different surface characterization techniques such as X-ray Diffraction, Scanning Electron Microscopy and Vickers’s micro-hardness testing. These investigations confirmed the formation of a compound layer on the plasma exposed surface. It was observed that the layer thickness initially increases and then decreases with nitriding time. Similar results were obtained for increasing filling gas pressure. The X-ray Diffraction results showed a down-shift in the original diffraction peaks, which confirms the nitrogen diffusion into the exposed surface and a compound layer formation. A significant improvement in the surface hardness was also vivid, which might be due to the nitrogen diffusion and the formation of a compound layer on the target surface.

Effect of sliding distance on abrasive wear modes transition

This work presents a study on the effect of sliding distance on abrasive wear modes transition in micro-abrasive wear. Ball-cratering wear tests were conducted with specimens of P20 cemented carbide (WC-Co) and M2 tool steel, balls of 52100 steel and abrasive slurry prepared with SiC particles and distilled water. Results were analyzed in terms of Ag (area with grooving abrasion) and Ar (area with rolling abrasion) as a function of sliding distance and pressure; they have indicated that with the increasing of sliding distance and, a consequent decreasing of pressure, there is the transition from grooving abrasion to rolling abrasion.

Influence of Cu additions on the mechanical and wear properties of NbN coatings

The influences of increasing copper content in the NbN–Cu coatings on mechanical and tribological properties were studied. The coatings were deposited on an M2 tool steel by using reactive magnetron sputtering. The copper content of NbN–Cu coatings was adjusted by controlling both the applied current to the Cu target and the dwell time of the substrate in front of the Nb and Cu targets. The copper content of the coatings was varied from 1 to 24at.%. The microstructure, microhardness and wear properties of the coatings were also examined. The addition of 1 and 5at.% Cu into NbN coatings modified the grain size and morphology. With the addition of 24at.% Cu, the coating structure changed into a multilayered one. Mechanically, the microhardness of the coatings except for NbN–24at.% Cu was increased by the addition of Cu. The hardness of the films reached the maximum level, 40GPa, at 1at.% copper content, while the hardness of the coatings decreased to 8GPa with the addition of 24at.% Cu. The addition of 1at.% Cu into niobium nitride showed a beneficial effect on the abrasive character of the coatings. The wear of the counter material has increased in these coatings without the occurrence of any wear damage on the coating side. Higher Cu content multilayer coatings showed very severe wear damage.

Microstructure and wear properties of AISI M2 tool steel on RF plasma nitriding at different N2–H2 gas compositions

Wear behavior of quenched-tempered AISI M2 tool steel samples has been studied after plasma nitriding at different N2–H2 plasma gas flows containing 25, 50 and 75sccm N2. Plasma nitriding was performed at 450°C for 8h under floating potential using a plasma reactor equipped with a radio frequency power generator. Microstructure, phase composition, nitrided layer thickness, hardness and surface roughness of the samples were studied using optical microscopy, X-ray diffraction, microhardness and surface profilometry measurements. Dry sliding wear resistance of samples was determined by performing ball-on-disc wear testes. The results revealed formation of mainly a diffusion zone at the 25sccm N2–75sccm H2 gas flow and mono-phase ε-Fe2–3N compound layer at higher N2 concentrations. Plasma nitriding increases near surface hardness up to 50% (about 1600HV0.025) irrespective of the N2:H2 ratio, where nitrided layer depth and surface roughness increase with increasing the N2 flow rate in the plasma gas. Depending on the nitrogen content, sliding wear resistance may be improved between 20 and 90% with respect to the un-nitrided substrate. Among the nitrided samples the maximum and minimum wear resistance was obtained at plasma gases containing higher and lower H2 fractions, respectively. Decreasing wear resistance with increasing N2 flow rate in the plasma gas attributed to formation of the hard and brittle compound (white) layer on the sample surface and development of residual stress profiles.