Search

In recent years, promising technique of deep cryogenic treatment (DCT) is taking a new step in improving properties of various materials, especially steels. This study is focusing on influence of selected heat treatment process involving deep cryogenic treatment on the microstructure and microstructural evolution of four different steel grades (bearing steel 100Cr6, cold work tool steel X210Cr12, hot work tool steel X38CrMoV5-3 and stainless steel X17CrNi16-2). The study was performed for different heat treatment conditions, focused on effectiveness of DCT when using different austenitizing and tempering temperatures. The evolution of the microstructure was investigated in a sequential manner with various analytical techniques. The study indicates that the microstructure and microstructural evolution and changes are strongly related to the chemical composition of steel and the predefined matrix microstructure. DCT increases precipitation of carbides and induce their more homogenous distribution. The magnitude of increased carbide precipitation after DCT is correlated with the higher carbon content, whereas the content of other alloying elements does not scale with the precipitation behavior. The obtained results indicate that incorporation of DCT with heat treatment with higher austenitizing and lower tempering temperature is the most suitable for improving steels’ properties with DCT, due to the stronger impact of DCT on the carbide precipitation and matrix modification.

The IHTC (Interfacial-Heat-Transfer-Coefficient) between 22MnB5 and KDAHP1 hot work tool steel during the hot stamping process is an important thermal parameter to reflect the heat transfer efficie...

This research focuses on specimen geometry and the associated surface roughness of H13 hot-work tool steel, processed using laser-directed energy deposition additive manufacturing, and varying both the powder feed rate and the laser scanning speed. Under the examined conditions, the test sample measurements of length and width did not vary, but the sample heights were significantly affected by the scanning speed. An increase in scan speed resulted in ‘underbuilding’, while a decrease resulted in ‘overbuilding’, as might be anticipated. The top surface roughness of the samples was found to be greater than the side surface roughness, due to the capture of extra powder particles. For the single-track and multitrack clad samples, the surface roughness was increased when decreasing the scan speed. The addition of a draft angle, when producing 3-D components, was shown to reduce the side surface roughness. Using a finer layer thickness results in overbuilding the target height, while a coarser layer thickness results in underbuilding. Finally, the surface roughness exhibited no clear trend when the layer thickness was changed.

In this study, the microstructure and mechanical properties of martensitic hot-work tool steel AISI H13 produced by laser powder bed fusion (LPBF) under argon atmosphere in different LPBF process t...

This review discusses in detail the process of hot forging and the types of machines involved and explains the die materials used for hot forging of the respective types of machines, such as vertical forging presses (friction presses), drop hammer forging presses and horizontal forging machines. Forging requires forging the metal using compressive forces. It investigates the chemical properties of die materials used in hot forging. The article covers the materials, the properties of the forging die inserts and the master die inserts. The hardness of the materials has been defined on the basis of the chemical composition and the heat treatment process, the heat treatment is widely used for tungsten-based and chromium-based hot work tool steel to achieve microstructure. This article ends with the required die content and uses it on the basis of the hardness of the billet utilized.

The AISI H13 is a chromium based, medium carbon content hot work tool steel which is widely used in hot working as well as cold working applications. These steels are very popular because of their key characteristics such as high hardness, high strength, high fracture toughness and high wear resistance. These steels are continuously subjected to high mechanical stresses and temperature fluctuations, fatigue and wear loss which results in limited die life. It is therefore necessary to improve the properties of these tool steels. One of the methods to improve the properties of these tool steels is with the help of conventional heat treatment. But no significant improvements in the properties were observed. From the literature survey, it is realized that implementation of cryogenic treatment can improve the properties of tool steel. In the present paper, cryogenic treatment on AISI H13 hot work tool steel is studied with the help of characterization techniques such as hardness, wear and microstructure study. One set of specimens were subjected to conventional heat treatment (HTT) viz. hardening at 1020 °C followed by double tempering at 500 °C. Another set of specimens were subjected to conventional heat treatment followed by deep cryogenic treatment at −196 °C and soft tempering at three different temperatures viz. 200 °C, 300 °C and 400 °C (HTTCT). A modified heat treatment cycle (HTCT) is also proposed with varying soft tempering temperatures viz. 200 °C, 300 °C and 400 °C and comparison is made with HTT and HTTCT. The specimens were tested for hardness, wear and microstructure study. The experimental investigation shows that cryogenically treated specimens shows significant improvement in the hardness and carbide density as compared to conventionally treated specimens. It is thus concluded that HTTCT cycle gives two times higher wear resistance than conventional heat treatment cycle (HTT) because of precipitation of fine tertiary carbides.

In the present study, two different commercial tool steels SKD-61 and SKD-11 were hardened to attain the similar hardness of 50 HRC (5.51 GPa) and nanoindentaion test was performed to obtain the nanomechanical properties of the hardened steels. Furthermore, wear behavior of these steels were investigated using tribo test with different combination of load and sliding velocity. FE-SEM along with EDS was used to examine the surface morphology of the hardened steels before and after the tribo test. Results showed similar wear behavior at low sliding velocity and low applied load for both the steels but with the increase in sliding velocity beyond 0.20 m/s, the specific wear rate of SKD-11 steel also increases. Whereas, wear of SKD-61 tool steel exhibited no sever changes. Microgroove with plastic deformation, micro cracks, adhesion and oxidation was observed as primary wear mechanism. It can be said that at high load and high sliding velocity, SKD-61exhibits better wear performance than SKD-11 tool steel.

Purpose This paper aims to experimentally determine the influence of the tool shoulder depth value on the structural and strength properties of the single lap joints made of 7075-T6 aluminium alloy made with friction stir welding (FSW) technology. The aim of the preliminary tests is to optimize the parameters of joining process of thin-walled structures such as the skin-stringer joint or skin-frame joint of the aircraft fuselage. The tests were carried out for materials commonly used in such structures, i.e. 1.6 mm thick sheet 7075–T6 aluminium alloy with cladding on both sides (cladding thickness 4% per each side). The layer of clad protects plates from corrosion. Design/methodology/approach This study shows the results of the investigation for the joining of 7075–T6 ALCLAD aluminium alloy sheets. The welding process was carried out on a computer numerical control milling machine SOLARUCE TA–20A. Linear FSW welding was performed using a commercial tool from RSS SCHILLING with the symbol 10–K–4–Z–M–O, which is fabricated of hot work tool steel. Constant parameters of the technological process were applied. The welding process was executed for different values of the shoulder depth ZS. Findings This paper investigated the dependence between the thinning of the welded material and the depth value of the tool shoulder during the FSW process. The influence of the depth value of tool shoulder on joint strength in the static tensile/shear test was also performed. With the increase of the depth of the tool, the size of flash and structures of the face of the joint changes as well (its annular surface resulting from the tool’s work and the accompanying process of material flow on the run-off side). Such conditions in the process require a proper tool depression to reduce the occurrence of flash and minimize material thinning to achieve high joint strength and maintain the conditions for plasticizing the material. Practical implications Based on the experimental tests carried out, a number of guidelines for the correct conduct of the welding process can be outlined. Originality/value Taking into account the various aspects of the process, the optimal range of the tool depth into the material is a value of approximately 0.06 mm. At this value, the face of the weld is not porous; the flash is easily removed; and the strength of the joint and the deformation of contact line are at an acceptable quality level.

Recently, micro-milling has been one of the most important technologies to produce miniature components, because optional geometrical structures can be machined with a high material removal rate. In terms of conventional dimensions, dynamic milling definitely signals the direction of development in modern technologies: dynamic milling results in higher productivity, better thermal circumstances, and increased tool life. The current paper gives a summary of the possible applications of dynamic milling tool paths in the case of micromachining. The major problems of this technology are the issue of minimum chip thickness and relatively large tool deformation. Different milling strategies, i.e. up milling and down milling, will be compared in detail. A systematic series of experiments were performed in order to generate data for the investigation. A special measuring system was established to perform related data collection. The experiments were carried out on a 5-axis micromachining centre using a tool steel workpiece with a hardness of 50 HRC. Based on the results of the experiments, the force components and the vibrations were also analysed at different radial depths of cut and different feed per tooth values, where productivity was also an important factor. It was found that dynamic milling can be applied in micro sizes, too. It is concluded that in the case of small contact angles, setting as high a feed per tooth value as 23.52 μm is also justified. During the investigation, optimal cutting parameters were also determined within the applied parameter range, these are ae = 34.80%, fz = 8.28 μm, and the use of the down milling strategy.

The microstructure and primary carbides in the steel billets produced by an industrial-scale electroslag rapid remelting (ESRR) at different melting rates were studied. The amount and size of primary carbides MC and M2C at the center of the remelted ingots is larger than that at the mid-radius of the remelted ingots. The amount of primary carbides and secondary dendrite arm spacing of the ingot increase with the increase in the melting rates of ESRR, caused by the increase in the local solidification time. The microsegregation of Mo in the remelted ingots after annealing is most serious among the carbide-forming elements. The microsegregation of Mo and Cr increases linearly with increasing the melting rate, and the microsegregation of V keeps nearly constant with further increasing the melting rate from 400 to 500 kg/h. Increasing the melting rate of ESRR do not change the types of primary carbides until 500 kg/h, at which another type of primary carbide M7C3 is formed. The amount of the primary carbides and the microsegregation degree of Mo, V and Cr in the ESRR billets at the melting rate of 400 kg/h is nearly same as that produced by same-scale conventional ESR.

H13 steel is a typical hot work die steel with good strength and toughness that is often used to manufacture high-temperature disk springs. However, disk springs occasionally fail after use in the petrochemical industry. Therefore, the effects of the quenching and tempering temperatures on the microstructure and mechanical properties of H13 steel after quenching and tempering processes are investigated herein. The results show that the lath width (lath) controls the strength of the H13 steel. The precipitated phases mainly comprise Cr23C6, Cr7C3 and VC. The coarsening of the Cr23C6 phase reduces the hardness, while reducing the dislocation density improves the toughness of the H13 steels after quenching and tempering. When the quenching temperature is 1040 °C and the tempering temperature is 570 °C, the H13 steel after quenching and tempering has a uniform microstructure with good strength and toughness.

In the past few decades, demand for precise miniature components has grown significantly. Modern production technologies required for the production of such components, including micro milling, have become extensively researched areas. In spite of the intensive research in this field, there are still many topics and aspects that merit investigation. Through a systematic series of experiments, this paper analyses the special characteristics of micro milling including cutting forces, vibrations, burr formation, and surface quality. A 5-axis micromachining centre with 60.000 rpm maximum spindle speed was used for the experiments carried out in the scope of this paper, and the machining of hardened hot-work tool steel (AISI H13) with a hardness of 50 HRC was investigated in detail. Also, a special measurement environment was prepared in order to collect machining data. Based on the results of the experiments, a power regression prediction model for cutting forces was created. As part of the analysis in the scope of the experiments, fast Fourier transformation was carried out in order to analyse the dynamic characteristics of the micro milling process, and to determine dominant frequencies. In addition, an analysis of variance (ANOVA) was applied to extensively analyse the main effects and interactions of different cutting parameters on different characteristics. Based on the investigations carried out in a comprehensive parameter range, an optimal parameter combination was also determined. The results of the experiments introduced in this paper contribute to a deeper understanding of the micro milling process, and this research provides information directly applicable in the industry.

Until now, additive manufacturing of high-performance materials such as martensitic hardenable tool steels is rarely investigated. This work addresses the introduction of an alternative alloying strategy for hot work tool steel powder, provided for laser powder bed fusion (L-PBF). The focus is on the question whether a powder mixture of spherical iron powder mixed with mechanically crushed ferroalloy particles can be processed by L-PBF, instead of using cost-intensive pre-alloyed gas-atomized powder, and to investigate the material properties associated with it. The particle morphology, packing density and flowability of this L-PBF powder feedstock is compared to gas-atomized spherical pre-alloyed steel powder and the results are correlated to the defect density, the resulting microstructure and the chemical homogeneity. Finally the resulting surface hardness is compared to a conventionally casted material as a reference state. It shows that the L-PBF fabrication of high-dense parts by means of both starting powders is technically feasible. Even though the alternative alloying concept promotes local chemical inhomogeneities within the microstructure, the overall porosity and the appearance of micro cracks are reduced.

Selected thermophysical properties of the hot work tool steel AISI H11 (1.2343) were measured in the temperature range from room temperature to the melting temperature. Thermal diffusivity was measured by the laser-flash method; heat capacity by differential scanning calorimetry; linear thermal expansion by push-rod dilatometry; and density at room temperature by an Archimedean balance. From these experimentally obtained data, thermal conductivity was calculated. Additionally, electrical resistivity of AISI H11 (1.2343) was measured by millisecond pulse-heating in the above mentioned temperature range. The measurement results of electrical resistivity as a function of specific enthalpy was combined with results of specific heat capacity measurements by differential-scanning calorimetry to obtain the relation between resistivity and temperature. Based on measured electrical resistivity and thermal conductivity, a Smith-Palmer-plot for the hot work tool steel AISI H11 (1.2343) is obtained for the ferritic and austenitic phases. No linear behaviour – as expected by the Wiedemann-Franz law – is observed in the ferritic phase region. In the high temperature austenitic region, the thermal conductivity can be computed from electrical resistivity using empirical constants of similar austenitic steels or superalloys.

Metal matrix composite materials are of high interest for their increased stiffness, strength or wear resistance. Wear resistant composites contain hard ceramic particles to reduce microcutting and grooving of the metal matrix surface. In this paper, a gas atomised hot work tool steel X40CrMoV5-1 (1.2344/AISI H13) was combined with fused tungsten carbide (FTC) particles in order to create forging tools with increased abrasive wear resistance. For that purpose, tool components were manufactured by sinter-forging of stacked powder layers to build up a graded hard phase concentration of up to 10 vol.-%. Subsequently, sinter-forged specimens were combined with basic hot work tool steel components and joined by diffusion bonding to assemble the complete tool. In order to evaluate their performance, the tools were examined in a hot backward can extrusion process of low-alloyed steel. Optical geometry measurements, light microscopy and scanning electron microscopy of the worn tool radii indicated a significant decrease in abrasive wear when using FTC-reinforced tools rather than conventional hardened tool steel.

Purpose This study aims to investigate the electrochemical corrosion performance of high velocity oxygen fuel (HVOF) sprayed WC–12Co coating in 3.5 Wt.% NaCl solution, which provided a guiding significance on the corrosion resistance of H13 hot work mould steel. Design/methodology/approach A WC–12Co coating was fabricated on H13 hot work mould steel using a HVOF, and the electrochemical corrosion behaviors of WC–12Co coating and substrate in 3.5 Wt.% NaCl solution was measured using open circuit potential (OCP), potentiodynamic polarization curve (PPC) and electrochemical impedance spectroscopy (EIS) tests. Findings The OCP and PPC of WC–12Co coating positively shift than those of substrate, its corrosion tendency and corrosion rate decrease to enhance its corrosion resistance. The curvature radius of capacitance curve on the WC–12Co coating is larger than that on the substrate, and the impedance and polarization resistance of WC–12Co coating increase faster than those of substrate, which reduces the corrosion process. Originality/value The electrochemical corrosion behaviors of WC–12Co coating and substrate in 3.5 Wt.% NaCl solution is first measured using OCP, PPC and EIS tests, which improve the electrochemical corrosion resistance of H13 hot work mould steel.

Since the popularization of press hardening in the early noughties, die and tooling systems have experienced considerable advances, with tool refrigeration as an important focus. However, it is still complicated to obtain homogeneous cooling and avoid hot spot issues in complex geometries. Additive Manufacturing allows designing cavities inside the material volume with little limitation in terms of channel intersection or bore entering and exit points. In this sense, this technology is a natural fit for obtaining surface-conforming cooling channels: an attractive prospect for refrigerated tools. This work describes a pilot experience in 3D-printed press hardening tools, comparing the performance of additive manufactured Maraging steel 1.2709 to conventional wrought hot work tool steel H13 on two different metrics: durability and thermal performance. For the first, wear studies were performed in a controlled pilot plant environment after 800 hot stamping strokes in an omega tool configuration. On the second, a demonstrator tool based on a commercial tool with hot spot issues, was produced by 3D printing including surface-conformal cooling channels. This tool was then used in a pilot press hardening line, in which tool temperature was analyzed and compared to an equivalent tool produced by conventional means. Results show that the Additive Manufacturing technologies can be successfully applied to the production of press hardening dies, particularly in intricate geometries where new cooling channel design strategies offer a solution for hot spots and inhomogeneous thermal loads.

This study presents investigations on the additive manufacturing of hot work steel with the energy-reduced gas metal arc welding (GMAW) process, which is a cold metal transfer (CMT) process. The paper analyses the influence of arc energy and the thermal field on the resulting mechanical properties and microstructure of the material. The investigations were carried out with hot work tool steel X37CrMoV 5-1, which is used for the manufacturing of plastic moulds, hot extrusion dies, and forging dies. The results show that this steel can be used to generate 3D metal components or structures with high reproducibility, near-net-shaped geometry, absence of cracks, and a deposition rate of up to 3.6 kg/h. The variation of the wire feed speed and the welding speed enables the production of weld beads of width up to 9.4 mm. The mechanical properties of the generated structures can be adapted by the dominant thermal field, which in turn is influenced by the bypass temperature and the electric arc energy. A determining factor to describe the main variables of the welding process is represented by energy per unit length EL. If the bypass temperature is above the martensite start temperature (Ms), there is a homogeneous hardness level along the height of the additively manufactured structure height as long as the energy produced by the welding arc is enough to keep the temperature of all layers above Ms.

The Stellite-6/WC composite coatings were produced on AISI H13 hot work tool steel by laser cladding with mixture of Co-coated WC (WC-12Co) particles and Stellite-6 powder. The phase composition, microstructural characterization, high temperature wear resistance and thermal fatigue behavior of Stellite-6/WC coatings were investigated and compared with the properties of the coatings produced from mixture of WC particles and Stellite-6 powder. The results showed that using the WC-12Co particles alleviated the decomposition of WC and resulted in the weaker intensity of W2C, CoCx and Co6W6C peaks in the X-Ray Diffraction (XRD) patterns. Compared with using the WC particles directly as the coating material, using the WC-12Co particles could further improve the wear resistance of coatings according to the relative lower width and depth of wear scars at the same WC content. In addition, fewer fatigue cracks were observed on the surface of coatings made by adding WC-12Co particles under the same thermal fatigue conditions, which indicates that using WC-12Co is beneficial to extend the life of Stellite-6/WC coatings.

Anti-wear performance of hot work tool steels is influenced by various parameters during their application lifetime as they are exposed to complex loading including heat, mechanical loading and sliding. Aim of this research work was to correlate different microstructures obtained by various heat treatments with hardness and anti-wear properties of hot work tool steel. For this purpose, modified 1.2367 hot work tool steel was used in this investigation. Two different austenitizing temperatures (1030 °C and 1150 °C) were used. Martensitic matrix was obtained after quenching, with two different austenitizing temperatures showing considerable difference in volume fraction of undissolved carbides (carbo-nitrides), being mainly vanadium rich MC type. Wear performance, which was influenced by austenitizing and tempering temperature, was evaluated by reciprocating sliding wear tests carried out at room temperature and pin-on-disc contact configuration. To simulate adhesive and abrasive wear component, 100Cr6 and Al2O3 balls were used as counter-body material, respectively. Lower wear rate at similar hardness over 50 HRc was observed comparing 100Cr6 counter-body results in favour to 1150 °C austenitized specimens where adhesive and abrasive wear components took place. Higher or comparable wear rate was obtained in the case of ceramic counter body where abrasive wear was prevailing.

Hot stamping is a well-established technology for producing safety relevant car components. The use of hot stamped components in modern car bodies offers the possibility of improving crash performance due to their high strength while simultaneously decreasing the fuel consumption by reducing sheet thicknesses and thus weight. Hot stamped components are mainly produced using the boron-manganese-alloyed steel 22MnB5. To prevent formation of oxide layer during heat treatment and subsequent forming process, AlSi-coatings are applied on the workpiece surface. Since hot stamped parts are formed at temperatures between 600 °C and 800 °C, no suitable lubricants have been found yet. Thus, severe wear and high friction occur during the forming process affecting final part quality as well as life-time of hot stamping tools. Consequently, measures for reducing tribological load during the forming operation have to be found in order to improve part quality and increase efficiency of industrial hot stamping applications. Within this study, the impact of the tool material on friction and wear is analyzed by comparing the tribological behavior of the newly developed high thermal conductivity hot work tool steel Thermodur 2383 Supercool with the reference material 1.2367. Both are characterized by means of flat strip drawing experiments under hot stamping conditions. The experiments are performed with different hardness values for each of the two tool materials. Furthermore, wear behavior is analyzed using scanning electron microscope and confocal microscope measurements of workpiece and tool. Hereby, fundamental wear and friction mechanisms within hot stamping applications are identified. The results of this study help to increase the process understanding regarding the tribological conditions during hot stamping. In future research work tool-side measures for increasing the life-time of hot stamping tools will be developed.

The aim in this article is to evaluate microstructural changes, hardness variations, and wear behavior of H13 hot work tool steel as a function of austenitizing and tempering temperature us...

Purpose: The purpose of this investigation was to determine the changes in the surface layer (Inconel 625), obtained during the laser treatment of tool-steel alloy for hot work by the use high-power fibre laser. Design/methodology/approach: Observations of the layer structure, HAZ, and substrate material were made using light and scanning microscopy. The composition of elements and a detailed analysis of the chemical composition in micro-areas was made using the EDS X-ray detector. The thickness of the resulting welds, heat affected zone (HAZ) and the contribution of the base material in the layers was determined. Findings: As a result of laser cladding, using Inconel 625 powder, in the weld overlay microstructure characteristic zones are formed: at the penetration boundary, in the middle of weld overlay and in its top layer. It was found that the height of weld overlay, depth of penetration, width of weld overlay and depth of the heat affected zone grows together with the increasing laser power. Practical implications: Laser cladding is one of the most modern repair processes for eliminating losses, voids, porosity, and cracks on the surface of various metals, including tool alloys for hot work. Laser techniques allow to make layers of materials on the repaired surface, that can significantly differ in chemical composition from the based material (substrate material) or are the same. Originality/value: A significant, dynamic development in materials engineering as well as welding technologies provides the possibility to reduce the cost of production and operation of machinery and equipment, among others by designing parts from materials with special properties (both mechanical and tribological) and the possibility of regeneration of each consumed element with one of the selected welding technologies.

One of the major advantages of micromachining is the high achievable surface quality at highly flexible capabilities in terms of the machining of workpieces with complex geometric properties. Unfortunately, finishing operations often result in extensive process times due to the dependency of the resulting surface topography on the cutting parameter, e.g., the feed per tooth, fz. To overcome this dependency, special tool shapes, called wipers, have proven themselves in the field of turning. This paper presents the transfer of such tool shapes to solid carbide milling tools for micromachining. In this context, a material removal simulation (MRS) was used to investigate promising wiper geometries for micro end mills (d = 1 mm). Through experimental validation of the results, the surface topography, the resulting process forces, and tendencies in the residual stress state were investigated, machining the hot work tool steel (AISI H11). The surface-related results show a high agreement and thus the potential of MRS for tool development. Deviations from the experimental data for large wipers could be attributed to the non-modeled tool deflections, friction, and plastic deformations. Furthermore, a slight geometry-dependent increase in cutting forces and compressive stresses were observed, while a significant reduction in roughness up to 84% and favorable topography conditions were achieved by adjusting wipers and cutting parameters.

The aim of this work is to develop a die material selection criterion for aluminum hot stamping applications. The criterion has been based on the back-to-back comparison of a set of reciprocating friction and wear tests. Three representatives belonging to different stamping die material families have been selected for the study: a cold work steel, a hot work steel, and a cast iron. These tool materials have been combined with an exemplary member from two heat treatable aluminum families: 2XXX and 6XXX. Each die-material/aluminum–alloy combination has been tested at three temperatures: 40, 200, and 450 ºC. The temperatures have been selected according to different stamping scenarios: long takt time press quenching, short takt time press quenching, and very short takt time hot forming without quenching, respectively. The results show that, among the three die material options available, the cold work steel turned out to be the most favorable option for high volume production and long takt time, the hot work steel fitted best for high volume production coupled with short takt time, and cast iron turned to outstand for short runs with prototype dies and for hot stamping without die quenching.

In recent years, hard turning, an alternative to grinding, which provides low cost and good surface quality, has become an attractive method to the manufacturers. In this experimental study, AISI H11 hot work tool steel that has been hardened up to 50 HRC was subjected to hard turning tests with coated carbide tooling. The analyses were carried out by applying response surface methodology with the analysis of variance method. A total of 27 experiments were modeled utilizing 3 3 full factorial design and were carried out using a CNC lathe. The effects of the cutting parameters on surface roughness, energy consumption, electric current value, and sound intensity level were investigated. Optimum cutting parameters and levels were determined according to these optimum values. The relationship between cutting parameters and output variables was analyzed with two-dimensional and three-dimensional graphics. The results show that while the most effective parameter on the surface roughness was the feed rate (88.62%), the most effective parameter on the sound intensity level was the cutting speed (44.92%). In addition, the cutting depth was the most effective parameter on both electric current (52.20%) and energy consumption (46.15%). Finally, regression coefficients were determined as a mathematical model, and it was observed that this estimated model gave results that were very similar to those achieved with real experiment (correlation values: 97.64% for surface roughness, 98.72% for energy consumption, 97.22% for electric current value, and 91.38% for sound intensity level).

This part of the study aimed to investigate the effects of cryogenic treatment applied to uncoated high speed steel (HSS) end mills on cutting forces (Fc), surface roughness (Ra), and tool life. The milling tests were performed at four cutting speeds (40, 50, 60, and 70 m/min), three feeds (0.018, 0.024, and 0.03 mm/rev), and a depth of cut (2 mm) under dry and wet conditions. Three categories of uncoated HSS end mills were used in the tests: conventional heat treated (CHT), cryo-treated (CT), cryo-treated and tempered uncoated (CTT), and TiAlN/TiN multilayer coated (MLC) end mills. The test results showed that the lowest values of Fc and Ra were measured with the use of MLC end mills. However, the cryogenic treatment provided in a reduction in Fc and Ra values. In addition, under wet conditions, the CTT end mills exhibited better performance than the CHT ones by 71.4%. The test results showed while cryogenic treatment is a useful and cheap application in steels, it does not have the ability to compete with coating technology in terms of tool life in milling of hot work tool steel. This paper is organized into two sections. In the first section, cutting performance of cryo-treated and multilayer coated end mills is evaluated. In the second section, performance comparison of cryo-treated WC-Co (Part 1), HSS (Part 2), and MLC end mills in milling of AISI H13 hot work tool steel is presented. Duzce University Scientific Research Project DivisionDuzce University [BAP - 2011.03.02.065] The authors wish to place their sincere thanks to Duzce University Scientific Research Project Division for financial support for the Project No: BAP - 2011.03.02.065. WOS:000632341800005 2-s2.0-85103206693

Conventionally, a defected tool steel is repaired by welding; however, that repairing does not guarantee homogeneous quality. Hence, this study focused on developing an alternative repairing technique using direct energy deposition (DED) to minimize thermal effects. To investigate a repair using powder-fed DED, AISI H13 powder was deposited onto heat-treated JIS SKD61. The deposited material was observed through scanning electron microscopy and its hardness and tensile properties were determined at 25, 200, 400, 600, and 800 °C. The deposited material showed different hardness distributions in its cross-section, revealing four representative features. The deposited region and dilution showed a hardness of 620 HV with a dendrite structure. The hardness decreased to 490 HV in the heat-affected zone, revealing a tempered martensite structure; however, it increased to 550 HV in the substrate and revealed a typical martensite structure. At all temperatures, the deposited material showed higher hardness than heat-treated SKD61. Moreover, it showed higher ultimate tensile strength and lower elongation in the deposited region. Therefore, this result indicates that without pre- or post-heat treatment, a part repaired using powder-fed DED can have better mechanical properties than heat-treated SKD61.

This paper focused on the performance of tungsten carbide end mills in machining of AISI H13 hot work tool steel under dry and wet conditions. The tool performance was evaluated in terms of resultant cutting force (Fc), average surface roughness (Ra) and tool life. In the milling tests, four categories of end mills were used: untreated (U), cryo-treated (CT), cryo-treated and tempered uncoated (CTT) and TiAlN/TiN multilayer coated (MLC). The tests were performed at four cutting speeds (80, 100, 120, 140 m/min), three feeds (0.08, 0.12, 0.16 mm/rev) and a depth of cut (2 mm). The test results showed that the lowest values of Fc and Ra were obtained with the use of MLC end mills. However, the cryogenic treatment was also effective on decreasing Fc and Ra. In addition, while the CTT end mills provided a slight improvement in tool life under dry conditions, they showed a remarkable improvement of 126.1% in comparison with the untreated ones under wet conditions. Although the CTT end mills exhibited a superior performance to U and CT ones, the MLC end mills were much more resistant to abrasive wear. This study is organized into two parts (WC-Co and HSS) to observe the effects of deep cryogenic treatment on performance of two different tool materials and to compare cryo-treated end mills with multilayer coated ones. This part is related to the cryogenic treatment of tungsten carbide end mills, whereas part two is regarding cryo-treated HSS end mills. Duzce University Scientific Research Project DivisionDuzce University [BAP - 2011.03.02.065] The authors wish to place their sincere thanks to Duzce University Scientific Research Project Division for financial support for the Project No: BAP - 2011.03.02.065 WOS:000632341800007 2-s2.0-85103008043

Turning parameters for cutting DAC-10 tool steel was optimized using surface response methodology (RSM). Turning was performed with TiAlN coated single point tool bit on CNC lathe. Cutting speed, feed rate, and depth of cut were considered as the cutting parameters and relative effect of process parameters on surface roughness and tool wear rate was analyzed. Outcomes revealed that feed rate and cutting speed are the governing parameters for surface quality and cutting speed for tool wear rate respectively. Optimization method confirms reasonable zone for responses and gives optimal condition for turning with cutting speed 150 m/min, feed rate 0.1 mm/rev and depth of cut 0.4 mm.

W360 is a hot work tool steel produced by voestalpine BÖHLER Edelstahl GmbH & Co KG, a special steel producer located in Styria, Austria. Surface tension and density of liquid W360 were studied as a function of temperature in a non-contact, containerless fashion using the oscillating drop method inside an electromagnetic levitation setup. For both, surface tension and density, a linear model was adapted to present the temperature dependence of these measures, including values for the uncertainties of the fit parameters found. The data obtained are compared to pure iron (with 91 wt% the main component of W360), showing an overlap for the liquid density while there is a significant difference in surface tension (− 5.8 % at the melting temperature of pure iron of 1811 K).

The increasing demand for complex components with filigree secondary functional elements promotes the application of new process technologies to extend the process limits of sheet-bulk metal forming (SBMF). The filling of cavities poses great challenges for manufacturing with sufficient quality. In cold forming, a considerable potential could be observed regarding mould filling, through a local adaptation of friction properties by surface structuring. In this study the transferability to hot sheet-bulk metal forming, which offers specific advantages due to thermal support, is to be investigated. The machinability of a hardened (53 HRC) hot work tool steel (HWS) AISI H11 by micro- and high feed milling is investigated related to tool wear and surface quality. Functional surface structures are applied on dies and adapted within the scope of hot sheet-bulk metal forming. Subsequent a developed hot ring compression test is to be used for tribological investigation of the structure-dependent material flow. In addition, an increase in the wear resistance of the structures by wet abrasive jet machining is to be focused on. Finally, the improvement of the surface modifications by introducing selected structures into a prototype tool is to be evaluated under real operating conditions with regard to their durability and mould filling.

The aim of this study was to evaluate the effect of dissolution of the small carbides residual from annealing and earlier processing, on the mechanical and wear properties of hot-work tool steel. Recommended as well as extreme austenitization temperatures (950 °C, 1030 °C and 1150 °C) with subsequent tempering were used aiming at same hardness level of specimens of same material. This allows correlation in wear resistance variation to the microstructural elements and variations in other mechanical properties of the investigated steel. M23C6 and MC are still present at the Taus = 950 °C, which are being dissolved with higher austenitization temperature. Optimal combination of mechanical properties are obtained at recommended austenitization. Specimens subjected to lowest austenitization showed the worst abrasive wear resistance.

In the below investigation, the impact of speed, feed, depth of cut, and workpiece hardness on the cutting temperature at tool-workpiece interface on hard-turning of the American Iron and Steel Institute (AISI) H13 tool steel parts will be investigated. It is worth noticing that the inclusion of workpiece hardness as an input variable in discussing cutting temperature wasn’t widely investigated in the literature. Dry cutting experiments were done and the outcomes showed that the cutting temperature is highly influenced by the workpiece hardness. Also, it was noted that though the effect of depth of cut is statistically insignificant, yet it was found that the cutting temperature is an increasing function of the cutting depth. Furthermore, a predictive model for predicting cutting temperature was developed using response surface methodology (RSM) and artificial neural network (ANN) based on the inputs. The mean relative error was employed for testing the adequacy of the created predictive models, and its value was 3.56% and 0.844% for RSM and ANN respectively. Moreover, the new optimization algorithm, cuttlefish algorithm (CFA) was employed for optimizing the cutting temperature and the results were compared with those from the genetic algorithm (GA). The CFA obtained the best results at the least convergence rate.

Shape memory alloys are generally produced by casting processes and are subsequently homogenized. However, to obtain semifinished products on an industrial scale, the ingots from the casting process must be hot worked. In particular, final bar and sheet products can be obtained by hot rolling process. During intense hot work, surface oxidation of the material and microstructural changes may cause modifications to its original thermomechanical properties. In this sense, the present work aimed to study the correlation of the superelastic behavior in a Cu-Al-Be-Cr alloy before and after subjecting it to the hot rolling thermomechanical process. Abnormal grain growth was observed for a hot rolled sample with 30% reduction in initial alloy thickness. This abnormal growth in relation to non-rolled alloy caused an increase in phase transformation temperatures, a reduction in residual strain, a reduction in induction stress and an increase in alloy superelasticity.

Currently, selective laser melting (SLM) is gaining widespread popularity as an alternative manufacturing technique for complex and customized parts, especially for hot-work and injection molding applications. In the present study, as the major factors for the failure of H13 hot-work die steels during hot-working, thermal fatigue (TF) properties of H13 processed by SLM and a conventional technique were investigated. TF tests (650 &deg, C/30 &deg, C) were conducted on the as-selective laser melted (As-SLMed), thermally treated selective laser melted (T-SLMed), and forged (Forged) H13. Results show that the As-SLMed H13 exhibited the best TF resistance properties among the specimens herein (the shortest total crack length and highest hardness of 687 &plusmn, 12 HV5), whereas the Forged H13 exhibited the poorest TF resistance properties (the longest total crack length and lowest hardness of 590 &plusmn, 11 HV5) after TF tests. TF resistance properties were closely related to the initial and final hardness. Further microstructural investigations revealed that the typical cell-like substructures, increased amount of retained austenite, and most importantly, refined grain size were the main reasons for the improved TF resistance properties in the As-SLMed H13 compared to the Forged counterparts.

This paper presents an experimental and numerical study into the influence of elevated temperatures on mechanical properties of the heat treated high quality hot work tool steel H11. This steel belongs to a group of alloyed steels with extraordinary mechanical properties. The aim of this study was to determine the highest temperature at which these properties are still maintained. The experimental investigation focused on the tensile testing of specimens at seven different temperatures, including the room temperature. The highest testing temperature was 700 °C. The heat treatment of plates (specimens) consisted of quenching and tempering. Although the strain hardening of this type of materials is small, the strain hardening curves were calculated to show if there was a possibility for the material to increase its strength due to exploitation loads. Also, a numerical analysis of the tensile test by using the finite element method was done in order to define an appropriate model for numerical testing. The obtained results are then compared with the experimental results.

The combination of additive and subtractive manufacturing processes is especially useful for repairing complex geometries and high-added-value components. The best solution for combining both processes is to integrate them in a single machine. Nevertheless, this combination entails a series of challenges, such as the impact that the use of cutting fluids in the subtractive operation may have on the subsequent additive process. In view of this situation, the present work aims to evaluate the effects of the deposition of AISI H13 hot work tool steel on a substrate impregnated with cutting fluid. For this purpose, different oil concentrations have been considered, and the attained results have been compared with the reference tests, performed on a clean substrate. In addition to morphological variations, it has been observed that when high oil concentrations are used, the deposited material is cracked, invalidating the parts manufactured through this approach. Therefore, in the case of AISI H13 tool steel, it has been determined that a cleaning stage is highly necessary in order to remove any cutting fluid that may be on the surface of the substrate before the additive operation is performed.; Fabrikazio-prozesu gehigarri eta kengarrien arteko konbinaketa oso erabilgarria da geometria konplexuko eta balio-erantsi altuko piezen konponketarako. Prozesuak bateratzeko aukera onena haiek makina bakarrean barneratzea da. Alabaina, bateratze horretan erronka anitz agertzen dira, besteak beste, mekanizazio-prozesuan erabiltzen diren ebaketa-jariakinek jarraiko gehitze-prozesuan izan dezaketen eraginaren ezjakintasunaren ondorioz.Egoera horren aurrean, berotako trokelgintzan ohikoa den AISI H13aren kasurako ebaketa-jariakinarekin kutsaturiko gainazalean laser bidez materiala eranstean ager daitezkeen akatsen azterketa gauzatu da. Olio-maila anitzekin egin dira saiakuntzak, eta gainazal garbian egindako erreferentziazko saiakuntzarekin alderatu dira lorturiko emaitzak. Aldaera morfologikoak nabaritzeaz gain, % 100 olio-kontzentrazioko ebaketa-jariakina erabiltzen den kasuan erantsitako materiala arrakalatu egiten dela ikusi da, eta egoera horretan fabrikaturiko piezak baliogabetu egiten dira. Hortaz, beharrezkoa dela ikusi da AISI H13aren kasuan gehitze-prozesuaren aurretik gainazalean egon daitezkeen ebaketa-jariakinen garbiketa .

Made available in DSpace on 2020-12-10T19:47:17Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-15 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Tool steels are applied in a variety of industrial operations providing a good balance of properties. Surface engineering has the potential to improve productivity and further extend the lifetime of metallic components. In the present work plasma nitriding is applied to the hot work AISI H13 tool steel to improve wear and corrosion characteristics. The steel was nitrided in the tempered condition at three different temperatures and pressures for 5 h of duration. At 450 degrees C of nitriding temperature mainly a diffusion zone is observed while a compound layer is produced at 550 and 650 degrees C. Both surface and bulk hardness decrease as nitriding temperature is increased. Xray diffraction indicates that a mixture of both epsilon and gamma' iron nitrides is produced in all cases. The content of epsilon-nitride appears to decrease with temperature while gamma'-nitride and CrN increase. Working pressure does not lead to significant alterations in phase proportion, hardness and wear resistance after plasma nitriding at a given temperature. However, increasing processing temperature, from 450 to 650 degrees C, reduces the wear coefficient from 1.19.10(-7) to 7.06.10(-8) mm(3)/N.m, respectively, while from the base steel such coefficients are in the order of 10(-5) mm(3)/N.m. Regarding the corrosion behavior, plasma nitriding at 450 and 550 degrees C yields higher corrosion potentials, lower current densities and an extensive passivation range, while the tempered substrate, irrespective the condition, exhibits no passivation. From the wear and corrosion perspective it is concluded that plasma nitriding at 450 or 550 degrees C leads to better corrosion properties while nitriding at 650 degrees C yields a better wear performance. Univ Fed ABC, Ctr Engn Modelagem & Ciencias Socials Aplicadas, Alameda Univ S-N, BR-09606045 Sao Bernardo Do Campo, SP, Brazil Univ Sao Paulo, Dept Engn Mat, Escola Engn Sao Carlos, Av Joao Dagnone 1100, BR-13563120 Sao Carlos, SP, Brazil Univ Estadual Paulista, Fac Engn Ilha Solteira, Dept Fis & Quim, Av Brasil Ctr 56, BR-15385000 Ilha Solteira, SP, Brazil Univ Estadual Paulista, Fac Engn Ilha Solteira, Dept Fis & Quim, Av Brasil Ctr 56, BR-15385000 Ilha Solteira, SP, Brazil

In this work, we have attempted to prepare a comparative machinability study of wire electrical discharge machining of different difficult-to-machine materials, viz., stainless steel (SS) 316, H21 hot work tool steel and M42 high-speed steel (HSS). The key features, which are compared during the analysis, are mainly material removal rate, average surface roughness, kerf width, wire consumption rate (WCR), recast layer (RL), elemental diffusion, surface morphology and micro-hardness of the machined surface. They are found to be greatly influenced by pulse energy. The pulse energy is calculated in terms of ‘specific discharge energy’. Apart from the discharge energy, the thermal conductivity of the material also plays an important role in the formation of RL and inclusion of foreign elements such as carbon, oxygen, copper and zinc in RL. H21 steel has been found to be more prone to thermal defects due to its high-thermal conductivity and high tensile residual stresses, whereas more re-solidification of foreign materials is observed in SS316 and M42 HSS due to their high adhesive properties and low-thermal conductivity. But, in low-energy cutting, more uniform surfaces are observed in H21 steel in comparison with other two types of steel.

A NiCrBSi alloy coating was sprayed on H13 hot work mould using a high velocity oxygen fuel. The surface and cross-section morphologies of obtained NiCrBSi coating were observed using a field emission scanning electron microscope (SEM), its phases were analyzed using an X-ray diffractometer (XRD). The friction-wear behaviors of NiCrBSi coating were investigated using a high temperature wear tester, the morphologies and chemical elements of worn tracks were analyzed using a SEM and its configured energy dispersive spectrometer (EDS), respectively. The results show that the average COF of NiCrBSi coating at 500, 600, and 700 °C is 0.4046, 0.4039, and 0.3975, respectively. The wear mechanism of NiCrBSi coating at 500 and 600 °C is abrasive wear, adhesive wear and oxidation wear, while that at 700 °C is abrasive wear and oxidation wear, the wear resistance of NiCrBSi coating is dependent on the compounds of Ni, Si and Cr.

Decarburisation is found as an undesirable consequence of the heat treatment cycle in hot work tool steels. In this work, an increase in the decarburisation resistance of tool steel through...

Dilatometry is a useful technique to obtain experimental data concerning transformation. In this paper, a dilation conversional model was established to calculate carbides fraction in AISI H13 hot-work tool steel based on the measured length changes. After carbides precipitation, the alloy contents in the matrix changed. In the usual models, the content of carbon atoms after precipitation is considered as the only element that affects the lattice constant and the content of the alloy elements such as Cr, Mo, Mn, V are often ignored. In the model introduced in this paper, the alloying elements (Cr, Mo, Mn, V) changes caused by carbides precipitation are incorporated. The carbides were identified using scanning electron microscope and transmission electron microscope. The relationship between lattice constant of carbides and temperature are measured by high-temperature X-ray diffraction. The results indicate that the carbides observed in all specimens cooled at different rates are V-rich MC and Cr-rich M23C6, and most of them are V-rich MC, only very few are Cr-rich M23C6. The model including the effects of substitutional alloying elements shows a good improvement on carbides fraction predictions. In addition, lower cooling rate advances the carbides precipitation for AISI H13 specimens. The results between experiments and mathematical model agree well.

The effects of two conventional heat treatments and one innovative processing by laser surface remelting of modified X37CrMoV5-1 tool steel on its abrasion wear resistance were investigated. Conventional heat treatments consisted of quenching from 990 °C, individually followed by two different tempering treatments to achieve secondary hardness either at 520 °C or 560 °C. Laser surface remelting was performed using optimized parameters of continuous laser beam scanning mode. The results showed that the highest wear resistance was obtained for almost carbide-free, surface remelted microstructure with the highest hardness due to microstructural refinement and martensitic transformation hardening. The observed differences in wear resistance among individual material states are discussed in relation to their microstructures, hardness, and wear mechanisms characteristics.

AISI H13 (4Cr5MoSiV1) is one of the commonly used materials for extrusion tool, and it suffers from fatigue–creep damage during the hot extrusion process. Stress-controlled fatigue and creep–fatigue interaction tests were carried out at 500 °C to investigate its damage evolution. The accumulated plastic strain was selected to define the damage variable due to its clear physical meaning. A new fatigue–creep interaction damage model was proposed on the basis of continuum damage mechanics. A new equivalent impulse density for fatigue–creep tests was proposed to incorporate the holding time effect by transforming creep impulse density into fatigue impulse density. The experimental results indicated that the damage model is able to describe the damage evolution under these working conditions.

The X40CrMoV5-1 (H13) hot work tool steel was densified by selective laser melting (SLM) using different laser parameters and preheating temperatures. The porosity and crack densities of the processed specimen were determined, the resulting microstructure characterized, tempering hardness diagrams recorded and the reusability of the powder assessed. The X40CrMoV5-1 steel showed a good densification behaviour. Relative densities of above 99.5% were obtained. After SLM densification, the specimen showed a fine-grained microstructure, with a cellular arrangement consisting of ferrite and austenite. Although the microstructure did not change with preheating temperature, a decrease in crack density could be observed for higher preheating temperatures. By combining microstructural observations with some simulations, a new model describing the microstructural evolution of SLM-densified X40CrMoV5-1 is suggested. The peak in secondary hardness after tempering SLM-densified X40CrMoV5-1 was observed at higher temperatures compared to the cast reference steel in the same heat treatment condition.