High Carbon Tool Steel Research Articles

Microstructural characterization of AISI 440C stainless tool steel fabricated by laser powder bed fusion

Abstract The microstructure of a stainless tool steel AISI 440C fabricated by laser powder bed fusion (L-PBF) without pre-heating of the build plate was characterized by multi-scale experimental methods. In combination with thermodynamic calculations, the solidification and cooling-down procedures were analyzed with the intention to understand the cracking behavior of high carbon tool steels processed by L-PBF. The results showed a fully austenitic structure in the as-built sample with sub-micro cellular structures and nano-sized carbides decorating the cell walls. Significant segregation exists merely at the intersection of cell walls while it is absent along high angle grain boundaries. Factors contributing to crack-free AISI 440C are discussed, providing guidelines for future L-PBF fabrication of high-carbon tool steels.

Processing of Niobium-Alloyed High-Carbon Tool Steel via Additive Manufacturing and Modern Powder Metallurgy.

Niobium is recently considered one of the potential alloying elements for tool steels due to the formation of hard and stable carbides of MC type. Its use is limited by the fact that these carbides tend to coarsen during conventional melting metallurgy processing. This work explores the potential of additive manufacturing for processing Nb-alloyed tool steel with a high content of carbon. Directed energy deposition was used as the processing method. It was found that this method allowed us to obtain a microstructure very similar to that obtained after the use of consolidation via spark plasma sintering when subsequent heat treatment by soft annealing, austenitizing, oil quenching and triple tempering for secondary hardness was applied. Moreover, the soft annealing process could be skipped without affecting the structure and properties when machining would not be required. The hardness of the steel was even higher after additive manufacturing was used (approx. 800-830 HV 30) than after spark plasma sintering (approx. 720-750 HV 30). The wear resistance of the materials processed by both routes was almost comparable, reaching 5-7 × 10-6 mm3N-1m-1 depending on the heat treatment.

Achieving exceptional wear resistance in a crack-free high-carbon tool steel fabricated by laser powder bed fusion without pre-heating

Laser powder bed fusion (LPBF) for the fabrication of dense components used for tooling applications, is highly challenging. Residual stresses, which evolve in the additively manufactured part, are inherent to LPBF processing. An additional stress contribution in high-carbon steels arises from the austenite-to-martensite phase transformation, which may eventually lead to cracking or even delamination. As an alternative to pre-heating the base plate, which is not striven by industry, lowering the martensite content which forms in the part, is essential for the fabrication of dense parts by LPBF of high-carbon tool steels which are then adapted to LPBF. In this study, a successful strategy demonstrates the processing of the Fe85Cr4Mo1V1W8C1 (wt%) high-carbon steel by LPBF into dense parts (99.8%). The hierarchical microstructure consists of austenitic and martensitic grains separated by elemental segregations in which nanoscopic carbide particles form a network. A high density of microsegregation was observed at the molten pool boundary ultimately forming a superstructure. The LPBF-fabricated steel shows a yield strength, ultimate compressive stress, and total strain of 1210 MPa, 3556 MPa, and 27.4%, respectively. The mechanical and wear performance is rated against the industrially employed and highly wear-resistant 1.2379 tool steel taken as the reference. Despite its lower macro-hardness, the LPBF steel (58.6 HRC, 0.0061 mm3 Nm–1) shows a higher wear resistance than the reference steel (62.6 HRC, 0.0078 mm3 Nm–1). This behavior results from the wear-induced formation of martensite in a microscale thick layer directly at the worn surface, as it was proven via high-energy X-ray diffraction mapping.

The macrosegregation behaviour of Fe-C-Cr-Mo type steel in laboratory scale model ingot.

In ingot casting, it is important to predict and control segregation and casting defects that occur during the solidification process, because they have a significant effect on the quality of the steel ingot. In some special steels, in typical Fe-C-Cr-Mo type high carbon tool steels, macro-segregation tends to be more pronounced due to their wide solid-liquid coexistence temperature range and molten steel properties such as relatively higher liquid viscosity than basic carbon steels. In order to investigate segregation and defect formation phenomena during solidification, many experiments have been conducted using specially designed laboratory scale model ingots that can induce partial difference of solidification to cause macrosegregation phenomena. However, these kind of experimental approaches for special steels are less conducted and influence of alloy types on the macrosegregation behaviour is still not well understood. In this study, a model ingot which have a steel chill ring in the middle region of a mullite mold was prepared, then Fe-0.45C(mass%) carbon steel, Fe-1C-1.8Cr(mass%) bearing steel and Fe-1C-8Cr-2Mo(mass%) high carbon tool steel were cast into 30kg ingots and the macrosegregation behaviour was investigated.

Study Leaf Spring for Punch in Press Tools

The development of technology in the material sector is currently very fast, it can be seen from the many uses of metal materials, especially in the mass production industry with certain specifications, such as stainless steel, high carbon steel, and tool steel. Home industries such as the manufacture of rings, pans, bottle caps, stove components and others often use these materials as materials to make tools called press tools. In this press tool, high carbon steel or tool steel is mostly used as a punch, but as the cost and difficulty of these materials make home industries suffer big losses for the manufacture of production tools. For this reason, through this study the authors conducted experiments in the laboratory on recycle leaf spring materials. The experiment was carried out in four stages of testing, namely composition test, tensile test, hardness test, and microstructure test. The composition of elements of the recycle leaf spring are 0.6627% Carbon (C), 0.7304% Manganese (Mn), 0.0240% Sulfur (S), 0.0257% Phosphorus (P). The tensile strength of recycle leaf springs is 1332.5 kg/mm2. The hardness is carried out with the Rockwell C hardness test, the result of the test is 52.5 HRC. There are elements of martensitic and austenite in the microstructure test. The results of the laboratory experiments were compared with the data in the literature, so this recycle leaf spring material could be used as a substitute for cutting blades in press tools.

Influence of preheating temperatures on material properties of PBF-LB manufactured hot-work tool steel X37CrMoV5-1

Processing of high-carbon tool steels with laser-based powder bed fusion (PBF-LB) can lead to thermal and stress-induced cracks. Defect-free processing is often realized by using base plate preheating. The temperature level during the building process is influenced by laser energy input and the surrounding conditions. Due to the layer-by-layer structure, heat treatment effects occur along the building height of the specimen, affecting the material properties. In-situ heat treatment can be used to reduce post-processing. A tempering process is required for preheating temperatures up to 500°C, which can be omitted at higher preheating temperatures.The hot-work tool steel X37CrMoV5-1 is processed at preheating temperatures between 200°C and 800°C. Base plate and top-level sample surface temperature are monitored during the building and cooling. The influence of heat treatment effects is discussed based on the microstructure, retained austenite and hardness along the building height.

The Critical Conditions and Kinetics Required for Dynamic Recrystallization in a High-Carbon Tool Steel

The Critical Conditions and Kinetics Required for Dynamic Recrystallization in a High-Carbon Tool Steel

Influence of the Method of Producing High-Carbon Tool Steel U10A on the Physical, Mechanical, Technological and Corrosion Properties

Purpose of research is study of the effect of the quality of the original charge on the complex of physical, mechanical, technological and corrosion properties of high-carbon tool steel U10A.Methods. High-carbon tool steel U10A, smelted at Tulachermet PJSC using metallized sponge iron pellets, scrap metal and a billet obtained by the fluidized slag blanket, has been chosen as the object of study. Steel was smelted in a three-ton arc furnace, subjected to out-of-furnace vacuum treatment in a ladle, cast into billets with a cross section of 280 × 320 mm and cooled slowly together with the furnace. Then, the obtained blanks were forged into a square of 150 × 150 mm (for making dies) and 40 × 40 mm (for samples) with cooling in sand and subsequent annealing. The experimental study of the chemical composition of U10A steel melts was determined by the method of photoelectric spectral analysis using an atomic emission spectrometer SA 2000 according to GOST 18895-97. Results. It has been found that the use of pure original charge has a positive effect on the properties of the melted metal. Steel U10A, smelted on the original charge, is not inferior in strength characteristics to steel on OMSH, surpassing the latter in terms of its plastic properties and especially in toughness. It is shown that steel smelted on the original charge is characterized by a lower content of micro-impurities, has less resistance to austenite decomposition and lower hardenability. It is revealed that, due to the lower stability of austenite, steel melted on the original charge must have a higher critical hardening rate, which should be taken into account when choosing heat treatment modes. It is established that the long-term strength of U10A steel in a medium that causes hydrogen cracking, largely depends on the heat treatment conditions and on the purity of the steel. Cleaner steel has a higher resistance to hydrogen cracking and, therefore, greater durability during operation.Conclusion. The results can be used to create resource-saving processes for processing metal alloys and composite materials.

PRODUCTION AND CHARACTERIZATION OF CA-PVD ZrN AND ZrCN COATINGS ON AISI D3 HIGH-CARBON TOOL STEEL

ZrN and ZrCN nanocrystalline coatings were produced on AISI D3 high-carbon tool steel by the vacuum-arc deposition technique with application of a modified curvilinear magnetic filter decreasing the amount of macroparticles and a new source of vacuum-arc plasma with improved performance which allowed enhanced deposition rates. The phase composition of the obtained coatings was analyzed via X-ray diffraction (XRD). The surface morphology and cross sections were monitored by scanning electron microscopy (SEM), whereas chemical composition was examined by using energy dispersive X-ray analysis (EDX). X-ray fluorescent analysis (XRF) was used to evaluate the thickness of the coatings. Tribological tests using the ball-on-disc method and measurements of Vickers microhardness have been carried out. Comparative mechanical and wear tests revealed enhanced tribological characteristics of zirconium-based coatings in comparison with the initial material.

Surface characteristics investigation of tool steel machined by powder metallurgy tool in EDA

Use of sintered tool electrodes for surface alloying by electrical discharge alloying (EDA) process has emerged as an alternating machining option with a view to improve surface properties. The present study identifies the appropriate process parameter settings to machine high carbon tool steel (En31) for higher surface finish using copper-manganese (Cu–Mn) powder metallurgy (PM) tool electrode. The effect of six different process parameters was evaluated using Taguchi’s experimental design and analysis of variance. The characterization of the surface alloyed with Mn and carbon was done by micro-hardness measurement, scanning electron microscope (SEM), atomic force microscope (AFM), energy dispersive x-ray spectrum (EDX) quantitative analysis and x-ray diffraction (XRD) technique. Also, the comparison was done with the surface machined using conventional Cu electrode. The surface machined with Cu-Mn PM tool electrode was found to be significantly alloyed with Mn and carbon having fewer micro-voids and no micro-cracks. Nano-size hillocks and valleys were found on the alloyed surface that is expected to improve the oil retention property of the surface. Presence of phases like Mn5C2 and Fe3C in the alloyed surface resulted in 95% and 33% higher microhardness than the base material and surface machined with conventional Cu electrode, respectively.

Effect of Deep Cryogenic Process on the Microstructure and Hardness and Wear Resistance of High Carbon Tool Steel

In this investigation, the effects of different heat treatment conditions on the mechanical properties of high carbon tool steel (SK2) were explored. Experimental results indicated that immediately doing deep cryogenic treatment can effectively reduce retained austenite after quenching. The moment of the holding time for the cryogenic treatment was extended can promote the fine carbides precipitated, and thus increased its hardness. The results of X-ray diffraction showed that the carbides in the matrix included Fe3C and Fe7C3.The wear test results demonstrated that the specimen with Q-T1hr-C24hr-T1hr treatment has the highest wear resistance than the others, which was caused by the effect of several tempering processes to improve toughness of the matrix and to precipitate considerable quantities of the fine carbides.

The occurrence of quenching cracks in high-carbon tool steel depending on the austenitizing temperature

Abstract Heat treatment has the greatest impact on the microstructure and properties, as well as the residual stresses and dimensional control of steel. Most of the problems that occur in heat-treated parts are attributed to improper heat-treatment practices, deficiency in the used grade of steel, poor part design or part defects. Inappropriate heat-treatment practices include overheating, burning, non-uniform heating, incorrectly selected austenitizing temperature and improper quenching. The formation of cracks during and after the quenching of austenitized steels is a major problem. As the carbon content of steel increases, the tendency to crack increases too. The tendency for quench cracking is also increased with higher austenitizing temperatures. The aims of the research were to determine the cause of the cracks in high‑carbon tool steel and to analyze the influence of the austenitizing temperature on the occurrence and propagation of quenching cracks. The results show that the main cause of quenching cracks is a too high austenitizing temperature caused by poor temperature control. A temperature that is too high leads to excessive austenite grain growth, distinctive grain boundaries with coarser martensite and the presence of retained austenite. On the other hand, the best properties and the absence of quenching cracks occur when C85S steel is quenched from a temperature below the Acm temperature.

Experimental Investigation on Hardness and Thermal Conductivity of D2 Steel Alloyed with Copper

High chromium high Carbon tool steel (D2 steel) is widely used for making moldsand dies as it possesses high hardness. The major concern in D2 is that the temperature of the mold increases with number of cycles of operation which is due to the insufficient heat transfer from the mold cavity to the surface. An additional cooling system can be provided to overcome the aforementioned problem but it leads to higher production cost and it complicates the mold design. As the effect of Copper on steels increases thermal conductivity, in the present study Copper is added to D2 in the composition varied in steps of 0.5% up to 2.0%. Specimens were fabricated using gas casting technique and heat treatment (quenching and tempering) was done. As the mold requires high strength, hardness and high thermal conductivity, hardness (Vickers) and thermal conductivity tests were conducted. Hardness test was taken using Vickers hardness testing machine and it was converted to the equivalent HRC and tensile strength. The maximum hardness value of 57.5 HRC was obtained at 2.0% Cu. Similarly, thermal conductivity test was taken and it was observed that maximum thermal conductivity of 25.3 W/mK was obtained at 2.0% of Cu. It was observed that the copper addition increases the thermal conductivity of the D2 steel proportionally. Micro structural analyses were also done and the images were discussed..

Anneal-Hardening Behavior of Cr-Fe-C Alloy Deposits Prepared in a Cr3+-Based Bath with Fe2+ Ions.

Cr-Fe-C alloy deposits were successfully prepared on high-carbon tool steel in a Cr3+-based electroplating bath containing Fe2+ ions and suitable complex agents. A Cr-based alloy deposit was obtained with an electroplating current density higher than 25 Adm−2, and a Fe-based alloy deposit was obtained using a current density of 20 Adm−2. Following electroplating, these alloy deposited specimens were annealed via rapid thermal annealing (RTA) at 500 °C for different periods up to 30 s. The experimental results show that Cr- and Fe-based alloy deposits could be significantly hardened after RTA at 500 °C for a few seconds. The maximum hardness was that of the Cr-Fe-C alloy deposit annealed at 500 °C for 10 s. The maximum hardness of 1205 Hv was detected from the annealed Cr-based alloy deposit prepared with 30 ASD. The hardening mechanism of annealed Cr- and Fe-based alloy deposits is attributed to the precipitation of C-related membranes. The hardness values of the annealed Cr- and Fe-based alloy deposits increase with the increasing degree of crystallization of the C-related membranes.

Experimental investigations of processing the high carbon cold-work tool steel 1.2358 by laser metal deposition for the additive manufacturing of cold forging tools

In the field of tool making, Laser Beam Melting of metals has been already used to fabricate injection moulds with complex inner cooling channels made out of the low-carbon maraging tool steel X3NiCoMoTi18-9-5 (1.2709). Furthermore, laser metal deposition (LMD) is an established technology for the repair of worn-out tools and the deposition of wear resistance coatings based on metal matrix composites. However, at the moment, the processing of high-carbon tool steels for the additive manufacturing of complete cold forging tools has only been investigated to a limited extent. Within the scope of the presented research, the processing of the high-carbon cold-work tool steel 60CrMoV18-5 (1.2358) by LMD is analyzed in detail. In this context, geometrically simple cuboidal structures are directly generated on dissimilar substrate plates made out of the hot-work tool steel X37CrMoV5-1(1.2343) via the application of various process parameter combinations. The manufactured cuboidal structures are metallographically prepared and subsequently analyzed with respect to substrate bonding, relative density, defect formation, microstructure, chemical composition, and microhardness. In this context, the influence of the particle size distribution of the used tool steel powder on the LMD process itself and the resulting relative density are extensively researched. For this purpose, high-speed camera measurements of the powder particle stream were conducted in order to determine both the powder particle stream diameter and the lateral powder particle distribution with regard to the distance z from the powder nozzle. Furthermore, the influence of an additional substrate preheating (maximum preheating temperature of 400 °C) on the resulting microstructure and hardness of the additively generated samples is the subject of the presented investigations.

Comparative Impact Behavior of High-C Steel After Conventional Quenching, Tempering, and Austempering

Abstract Usually bainitic microstructures exhibit good toughness and austempering is typically the preferred heat treatment when toughness is the primary requirement of the component. Several reports have shown such characteristics when compared to tempered martensite. High-carbon steel may exhibit brittle characteristics but it is a good steel with respect to mechanical properties and wear resistance. The objective of this study was to compare the impact properties of AISI O1, a high-carbon tool steel, designated VND in Brazil. This was done by comparing Charpy impact strength under different heat-treatment cycles. Steel test specimens were quenched from 820°C and tempered at 450°C to obtain tempered martensite, then austenitized, cooled, and held at 350°C to obtain bainite by holding at temperature for 20, 40, and 60 min. Because hardness influences impact behavior, comparative studies were performed at the same surface hardness level. The austempered samples with bainite microstructures obtained at a constant temperature and, by varying holding times, exhibited lower impact properties as compared to the quenched and tempered condition.

Finite strain formulation of elasto-plasticity without yield surface: theory, parameter identification and applications

In this study, a finite strain formulation of elasto-plasticity without the yield surface is analyzed. It is found that the presented model allows for a good description of the elasto-plastic response for many metallic materials. Furthermore, it is noted that the model involving a limited number of material parameters is able to capture such effects as indefinite elastic limit, strain hardening, strain softening and the Bauschinger effect. An algorithm for the evaluation of constants is described and the determined values are given for NC high carbon tool steel, copper, brass, Inconel alloy, tungsten heavy alloy and aluminum.

Tensile fracture behavior of Ni- and Cr–C/Ni-coated high-carbon tool steel (AISI 1090)

The tensile fracture behavior of Ni- and Cr–C/Ni-coated high-carbon tool steel specimens was studied. The Cr–C coating was prepared in a Cr3+-based plating bath, and the Ni coating was prepared in a Ni-sulfate bath. The experimental results indicate that the yield and ultimate tensile strengths were not changed after Ni- or Cr–C/Ni-coating. However, the elongation percentage of the steel specimen was clearly reduced after Cr–C/Ni-coating. According to the fractography study, the fracture feature with necking and a cup-and-cone appearance was observed in the steel and Ni-coated steel specimens after the tensile test. However, the fracture feature of the Cr–C/Ni-coated steel specimens with relatively low elongation percentages exhibited an obvious cracking plateau. Under the application of tensile stress, cracks in the Cr–C coating propagated through the Ni coating and then into the steel substrate, forming a cracking plateau and, decreasing its elongation percentage. Moreover, branch cracking was observed during crack propagation to develop a fracture appearance with some cracks and crack facets.

Tailor-Made Forging Tools by Laser Metal Deposition

The desire for individualized products forces the companies to a great diversity of combinable parts. This way, the clients can compile their personalized product. As this trend is not just limited on visual parts but also for functional components, laser additive manufacturing of metals is used more and more often in manufacturing. To bring more additive manufacturing into mass production, Laser Beam Melting and Laser Metal Deposition will be qualified for the use in tool manufacturing within the Bavarian research association “ForNextGen – Next Generation Tools”. The first subproject within this research association investigates the potential of Laser Metal Deposition in the production of hot and cold forging tools. Within initial tests optimized process, parameters for the processing of the hot-work steel 1.2709 are determined by single welding beads. The achieved density and the inner structure are analyzed within cubes that were built with the investigated parameters. As forging tools are usually made of high-carbon tool steel, the processing of materials with a rising percentage of carbon will be part of further investigations.

Influence of Processing and Heat Treatment on Corrosion Resistance and Properties of High Alloyed Steel Coatings

Corrosion and abrasive wear are two important aspects to be considered in numerous engineering applications. Looking at steels, high-chromium high-carbon tool steels are proper and cost-efficient materials. They can either be put into service as bulk materials or used as comparatively thin coatings to protect lower alloyed construction or heat treatable steels from wear and corrosion. In this study, two different corrosion resistant tool steels were used for the production of coatings and bulk material. They were processed by thermal spraying and super solidus liquid phase sintering as both processes can generally be applied to produce coatings on low alloyed substrates. Thermally sprayed (high velocity oxygen fuel) coatings were investigated in the as-processed state, which is the most commonly used condition for technical applications, and after a quenching and tempering treatment. In comparison, sintered steels were analyzed in the quenched and tempered condition only. Significant influence of alloy chemistry, processing route, and heat treatment on tribological properties was found. Experimental investigations were supported by computational thermodynamics aiming at an improvement of tribological and corrosive resistance.