AISI M2 Tool Research Articles

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.

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.

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.

Wear resistance of direct-energy–deposited AISI M2 tool steel with and without post-heat treatment

Wear resistance of direct-energy–deposited AISI M2 tool steel with and without post-heat treatment

Enhancing the adhesion strength and wear resistance of nanostructured NiCrN coatings

NiCrN coatings, with varying Ni contents, were deposited on AISI M2 tool steel substrates using closed field unbalanced magnetron sputtering ion plating (CFUMSIP) where the NiCr target current (INiCr) was varied. An evolution of the graded columnar structures was found in these coatings, where increased incorporation of nickel induced grain refinement, as well as a reduction in values of both hardness (H), elastic modulus (Er) and elastic recovery (We). The influence of variations in the microstructure and mechanical properties on the adhesion behaviour and tribological performance of these NiCrN coatings was investigated. Scratch test results demonstrated that higher critical loads (Lc1 and Lc2) suppressed both cohesive and adhesive failure in coatings which exhibited higher values of H/Er, H3/Er2 and We. The failure mode under progressive scratch loading was controlled by the hierarchical design of the NiCrN coatings that enhanced adhesion and prevented crack propagation through the coating. For the coatings with lower Ni contents improved wear resistance was ascribed to not only higher H/Er, H3/Er2 and We values of these coatings, but also the graded interlayers that delocalised the stress distribution during dry sliding.

Harmonizing mechanical responses of nanostructured CrN coatings via Ni additions

CrN coatings are often brittle and prone to abrupt failure. Incorporation of Ni is known to have significant effects on the chemical composition, microstructure and mechanical behaviour of chromium nitride coatings synthesised by PVD, and thus imparting toughness. In this study, a series of NiCrN coatings, with varying Ni concentrations, were deposited onto AISI M2 tool steel substrates through closed-field unbalanced magnetron sputtering ion plating (CFUMSIP). The phase compositions, microstructure, mechanical properties and deformation behaviour of the coatings were characterised by XRD, AFM, FIB, TEM/EDS and indentation testing. Residual stresses of these as-prepared coatings were measured by the XRD-sin2ψ method. A columnar structure was observed in all coatings, although grain refinement at higher NiCr target currents was noted. High hardness values of ~20 GPa were found in the coatings with the lower Ni (~5–14 at%) contents, associated with the effects of solid solution hardening, high compressive residual stress and grain refinement. Moreover, significant damage-tolerance, coupled with good hardness values (greater than ~12 GPa), was found in the NiCrN coatings deposited at INiCr ≥ 2 A. The presence of a metallic nickel-rich phase, together with nanoscale porosity, may contribute to stress dissipation and help maintain structural integrity.

Plasma nitriding of AISI M2 steel: performance evaluation in forming tools

ABSTRACTPlasma nitriding is a thermochemical treatment to improve the surface properties of metallic materials, such as mechanical and tribological properties. The aim of this study is to compare the nitriding performance of conventional plasma nitriding (CPN) and cathodic cage plasma nitriding (CCPN) for AISI M2 tool steel at various temperatures (400°C, 450°C and 500°C). The forming tool is also processed in identical conditions, and its productivity performance in the manufacturing of nails for civil construction is also evaluated. The highest hardness is achieved while processing samples at 400°C, and better productivity performance while treating samples at 500°C, both in CPN and CCPN. Notably, the hardness and productivity performance achieved in this study, particularly using CCPN is significantly higher than the forming tool provided by the factory in which conventional processing techniques were used, and thus it suggests the effectiveness of CCPN in wide-scale industrial applications in forming tools.

The Effects of Cryogenic Process on the AISI M2 Punch Materials and on the Hole Edge Geometry of the DIN EN 10111‐98 Sheet Metal Control Arm Parts

In this study, not only the effects of cryogenic processing on the wear of AISI M2 punches but also the effects of punch wear on the hole edge geometry of DIN EN 10111‐98 sheet metal control arm parts were investigated. The hole geometry changes are generally associated with punch wear and process parameters. Piercing operations were performed using eccentric press on 2.5‐mm‐thick sheet metal control arm parts with circular and slot AISI M2 tool steel punches. The punches were traditionally heat treated. The others were cryogenically treated at −145°C in addition to the conventional heat treatment. Weight losses were measured for punch wear assessments; furthermore, SEM and OM images were analyzed. The hole edge geometries of the selected parts were measured with a contour measuring machine in the specified number of blanks. So, no damage was done to the products for measurements. The cryogenic process resulted in a significantly low amount of retained austenite and caused uniformly distributed thin carbide precipitates. Reduction of retained austenite and formation of fine carbide particles led to increase in hardness values. It was found that untreated circular punch wear weight losses were approximately 40% higher than those of cryogenically treated samples. The untreated slot punch change rate was about 106% higher than that of the cryogenically treated samples. The wear process during the punching was faster and greater for the untreated punches. Fatigue microcracks were more common at the cutting edge of the untreated punches. However, abrasive wear was generally observed in cryogenically treated punches. The edge geometry values in the circular holes were at least two times higher than those in the slot holes of untreated samples. At the end of the industrial piercing process, it was determined that the M2 tool steel punch wear rates were decreased by cryogenic treatment, and the size changes of the hole geometry of the punches of the DIN EN 10111‐98 control arm parts were more economic and with a better quality.

Nanostructured molybdenum nitride-based coatings: Effect of nitrogen concentration on microstructure and mechanical properties

Molybdenum nitride (MoNx) coatings were deposited onto AISI M2 tool steel substrates (hardened to HRC 60) by magnetron sputtering. The nitrogen content was controlled by means of a closed-loop optical emission monitor. The coating microstructure was examined by X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. This showed that the increased nitrogen content led to a transformation from body-centered cubic α-Mo phase to γ-Mo2N phase (NaCl-B1 type) and then to a face-centered cubic MoN phase. The mechanical and tribological properties of these coatings were evaluated by nano-indentation, wear and scratch testing. The γ-Mo2N coating showed the highest hardness and the highest values of H (hardness)/E* (effective elastic modulus) and H3/E* ratio. During scratch and wear tests, the γ-Mo2N coating exhibited the best resistance to deformation and the lowest wear rate.

Steel components for packaging devices in sliding/rolling contact: Metallurgical failure analysis

This paper presents a case study in sliding/rolling contacts between steel components operating in packaging devices for powder pressing, where the non-conformal contact involving a rotating roller (AISI M2 tool steel) and pins (AISI 440B martensitic stainless steel) led to the formation of macro- and micro-pitting on both mating surfaces. On the basis of metallurgical failure analysis, surface-origin contact fatigue was identified as the main damage mechanism. Microstructural stress raisers such as relatively large carbides, clustered along plastic flow lines, were observed in both steels. A white etching layer (WEL), due to severe sliding/rolling conditions, further enhanced the formation of surface-origin cracks on the roller.

Thermal stresses computation under high–current pulsed radiation of AISI M2 tool steel

Surface modification of metallic materials and alloys with concentrated energy flows (powerful electron beams and ion plasma flow, laser beams) has been widely used in various fields of manufacturing. The aim of physical and mechanical properties modification is to improve the performance of the critical parts fabricated from modified materials. The mentioned energy impacts give rise to radiation, thermal and mechanical effects causing the changes in morphology, microstructure, elemental and phase composition of the surface layers, which in turn may lead to hardness, wear corrosion resistance and red hardness increasing of modified materials. However, as experimental investigations are shown, in some cases irradiation promotes the crystal defects’ occurrence and often non-uniform heating leads to the cracks’ formation in the surface layers. Thus, selection of incident electrons energy, its current density and pulse duration, taking into account the thermal stress state, is an actual problem of modern radiation technologies. This paper provides a numerical solution of differential equations in partial derivatives for the temperature fields’ computation as well as radial and axial thermal stresses distribution in R6M5 (AISI M2) high-speed steel exposed to medium-energy (up to 400 keV) high–current (up to 1 kA/cm2) pulsed (up to 1 μs) electron beam radiation. The obtained results can be useful in the optimal modes selection of tool steels and products at surface radiation treatment and evaluation of their service life.

Surface Treatment of AISI M2 Tool Steel by Laser Melting

Attempt was made to improve the surface hardness and wear properties of AISI M2 high speed tool steel. Laser surface melting (LSM) of tool steel was conducted with 2.2 KW Nd:YAG laser as heating source. Conventional hardening of the tool steel was applied. Characterizing the LSM, with optical and field emission scanning electron microscopy and surface hardness technique was used to evaluate the micro-hardness and mechanical behaviour of different regions of melting pool. AISI M2 tool steel is approximately HV 260, hardness after conventional treatment was 850 HV and the hardness after laser surface heat treatment is around 900 HV. It was found that there is a considerable influence of the laser power density and scanning velocity on the melted zone dimensions and the re-solidified structure. Increasing laser energy and reducing the laser scanning rate results in deeper and wider melt pool formation.

Deep Cryogenic Treatment of AISI M2 Tool Steel and Optimisation of Its Wear Characteristics Using Taguchi‘s Approach

The present research paper focuses on optimisation of wear test parameters for different deep cryogenic treated AISI M2 tool steel material. Commercially available, AISI M2 tool steel material is machined as per ASTM G99-05 standards and was subjected to deep cryogenic treatment for the different holding time of 12, 24 and 36 h, followed by tempering for 2 h at $$150\,^{\circ }\hbox {C}$$ . The specimens were tested for their wear resistance using a pin-on-disc wear testing setup adopting Taguchi‘s design of experiments approach. The control variables selected were deep cryogenic treatment holding time, the speed of the rotating disc and load applied to the specimen pin. The wear test was conducted as per trials generated by Taguchi‘s $$\hbox {L}_{27}$$ orthogonal array, and the results are analysed using signal-to-noise ratio and analysis of variance. The results show that the cryogenic holding time has majorly affected the wear resistance followed by the load on the pin and disc speed. It is also observed that 24 h holding time for deep cryogenic treatment yields better wear resistance compared to 12 and 36 h. Microstructure and X-ray diffraction analysis of the cryogenically treated specimens reveals the conversion of retained austenite into martensite and the formation of fine carbides in the martensite lattice after deep cryogenic treatment process which are responsible for the increase in wear resistance. Also, the worn surface analysis shows that the adhesion wear, oxidation wear and abrasion wear are the predominant wear mechanisms observed under different testing conditions.

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

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.

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.

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.

Study of the solidification of M2 high speed steel Laser Cladding coatings

High speed steel laser cladding coatings are complex because cracks appear and the hardness is lower than expected. In this paper AISI M2 tool steel coatings on medium carbon AISI 1045 steel substrate have been manufactured and after Laser Cladding (LC) processing it has been applied a tempering heat treatment to reduce the amount of retained austenite and to precipitate secondary carbides. The study of metallurgical transformations by Scanning Electron Microscopy (SEM) and Electron Back Scattered Diffraction (EBSD) shows that the microstructure is extremely fine and complex, with eutectic transformations and MC, M 2 C and M 6 C precipitation. Therefore, after the laser coating is necessary to use post-weld heat treatments.

Effects of deep cryogenic treatment on the dry sliding wear performance of ferrous alloys

In this study, the effects of cryogenic processing on the dry sliding wear performance and microstructural features of five common engineering materials were investigated. Significant improvements were found in the wear performance of a pearlitic low carbon steel brake material, as well as AISI A2, D6 & M2 tool steels. Optical and scanning electron microscopy of selected specimens indicated a range of changes due to deep cryogenic treatment including graphite flake degradation and pearlite refinement in cast iron and low carbon steel that was previously unreported in the literature. In tool steels, carbide precipitation and microstructural uniformity reported by other investigators was observed. Macro- and micro-hardness testing revealed no significant changes in any of the materials except for the low carbon steel tested, in which measured improvements were judged to be as a result of the refinement of the pearlite matrix due to deep cryogenic treatment.