Tool Steel Research Articles

Measurement of precision and quality characteristics of lattice structures in metal-based additive manufacturing using computer tomography analysis

Additive manufacturing, especially lattice structure fabrication, has garnered interest for its potential in high-precision aerospace and medical applications. Due to porosity and dimensional variation, obtaining mechanical characteristics and accuracy remains a research priority. This study addresses the current knowledge gap by providing a comprehensive methodology for the qualitative evaluation of cellular structures in additive manufacturing, focusing on the critical parameters of relative density, dimensional deviations, and porosity characteristics. The research utilizes advanced μCT analysis to investigate the impact of these factors on the overall quality and functionality of printed objects, particularly in metallic lattice structures fabricated using Laser Powder Bed Fusion (LPBF) technology. The cell structures were constructed using MS1 tool steel as the material base. An extensive investigation was carried out on a diverse array of lattice configurations, including Body-Centered Cubic (BCC), Diamond, Fluorite, Kelvin, Schwarz, and Fischer – Koch. It was observed that discrepancies between actual and designed relative densities in structures such as BCC, Diamond, and Kelvin indicate densification attributable to the manufacturing process, particularly in smaller cell structures. Furthermore, global porosity analysis demonstrated a clear relationship between increased density and reduced porosity. Optimal manufacturing conditions for minimizing defects and enhancing the precision and quality of additive manufactured metallic lattice structures were identified as a cell size of 3 mm and a 50 % relative density.

Implementation of hybrid CryoMQL sustainable lubri-cooling to enhance the grindability and surface integrity of tool steel

The current demand for surface finishing processes that are both technically proficient and environmentally friendly is increasing, necessitating the advancement of more efficient sustainable methods. Minimum quantity lubrication (MQL) provides excellent lubrication in the tool-work interaction but insufficient cooling impact. Besides, cryogenic enhances the chilling effect but has inadequate lubrication. This research revealed the synergistic impact of hybrid CryoMQL with eco-friendly Al2O3 NFs while grinding AISI D2 tool steel. CryoMQL facilitates the application of MQL-based soybean oil and deionized water (SO+DW) emulsion with 0.5 wt% and 1 wt% concentration of Al2O3 NPs and liquid nitrogen (LN2) through two individual nozzles in the cutting region. The results indicated that CryoMQL reduced grinding force (tangential force, Ft, and normal force, Fn), specific grinding energy (Ug), surface roughness (Ra), and grinding temperature (Tg) by 3.64–25.66 % in Ft, 3.52–12.87 % in Fn, 3.64–25.66 % in Ug, 8.81–25.02 % in Ra and 57.59–58.30 % in Tg, respectively, compared to MQL environment at 0.04 mm downfeed and 150 mm/s table feed rate. Eventually, it was observed that 1 wt% Al2O3 NFs improve Ft, Fn, Ug, Ra and Tg by up to 32.71 %, 20.33 %, 32.71 %, 23.55 %, and 6.81 % in comparison to 0.5 wt% Al2O3 NFs in the CryoMQL mode. The effectiveness of Al2O3 nanofluids with CryoMQL has resulted in good tribological conditions in the grinding zone with enhanced cooling/lubricating action of vegetable oil. Furthermore, negligible chip adhesion over finished surfaces was seen with 0.5 wt% and 1 wt% Al2O3 NFs under CryoMQL grinding. This study provides numerous scientific assistance in the automotive and tooling sectors, such as a better selection of environmentally friendly coolants and sustainable parameters for excellent surface properties, to provide the solution to highly complex and close tolerances of tool steel parts using CryoMQL finishing.

On the fatigue behavior of a tool steel manufactured by powder bed based additive manufacturing—a comparison between electron- and laserbeam processed AISI H13

In recent years, additive manufacturing (AM) techniques have gained increased attention. The most common AM technologies to realize complex parts are powder bed-based fusion processes, especially electron beam powder bed fusion of metals (PBF-EB/M) and laser-based powder bed fusion of metals (PBF-LB/M). Focusing on industrial applications, cyclic loading scenarios and fatigue properties of components produced by such techniques came into focus of research. The present work deals with a comparison between microstructure, hardness, density and fatigue properties of a high-alloy tool steel AISI H13 (1.2344, X40CrMoV5-1) manufactured by PBF-EB/M and PBF-LB/M. The investigated specimens are characterized by a complex phase composition containing ferrite, perlite, bainite and martensite, eventually resulting in different hardness values depending on the used AM technology. Fatigue data for PBF-EB/M AISI H13 are reported for the first time in open literature. It is shown that the fatigue behavior is significantly influenced by the specimen density. Accordingly, parts with a high density are characterized by superior fatigue strength.

Influence of Cell Structure on Yield Strength and Strain‐Hardening Behavior in Additively Manufactured H13 Hot Work Tool Steel

Mechanical properties including yield strength, hardness, and strain hardening are superior in additively manufactured H13 hot work tool steel (AMH) compared to conventional H13 (CMH), which are correlated with microstructural characteristics. Comprehensive microstructural analysis reveals that the strain is highly localized in the cell structure with retained austenite in AMH. Quenching and tempering (QT) heat treatment removes the cell structure and retains austenite from AMH, resulting in a microstructure and mechanical properties similar to CMH after QT. The constitutive equation for yield strength shows that retained austenite with sufficient amount of dislocation density in martensite contributes to higher yield strength in AMH than CMH and identical strengthening mechanism between AMH and CMH after QT. Furthermore, microstructural changes during plastic deformation are investigated to find the origin of high strain‐hardening rate in AMH. The relationship between hardness and indentation depth yields the higher statistically stored dislocation density in AMH than CMH. In addition to higher dislocation accumulation, transformation of retained austenite to α′ martensite results in transformation‐induced plasticity effect, which contributes to strain hardening.

Study of the effect of macrogeometry of rubbing steel bodies at their point contact on the tribological characteristics of lubricants under boundary lubrication conditions

The effect of the shape of contacting nonconformal elements of friction units that form an initial point contact on the tribological characteristics of lubricants during friction in the boundary lubrication mode. Point contact of rubbing bodies is realized on four-ball friction machines when testing tribological characteristics of lubricants in accordance with Russian GOST 9490–75 and GOST 23.221–84 Standards.However, these tests are carried out with the friction of standard bearing balls and does not allow taking into account the impact of materials of rubbing bodies on the results of the experiment. Therefore, two alternative designs of mandrels were developed, which allow implementation of two friction schemes: «rotating ball clamped in the spindle of the machine – three roller face planes» and «rotating ball — three cylindrical rollers». The load on the friction unit for both friction schemes, as well as in parallel on the mandrel under testing, in which three balls are installed, is the same (108 N), the spindle rotation speed is equal to 1 rpm, duration of testing is 60 min. The diameter of balls used in these experiments was 12.7 mm, and diameters of rollers were 5 and 8 mm, respectively. The material of samples was ShKh-15 tool steel or its 100Cr6 analogue. The designs of mandrels and the dimensions of samples were chosen in such a way that in all cases the contact areas of the experimental samples with the wearing (upper) ball would lie on a circle with a diameter of 7.32 mm. The tests were carried out under dry friction, and in boundary lubricated conditions in a PAO-4 polyalphaolefin oil medium, as well as in the same oil medium with the additives of oleic acid and DF-11 (a solution of zinc dialkyldithiophosphate in a low-viscosity oil). It is shown that the composition of a lubricating medium has a decisive effect on the test results (i.e., on the values of the friction coefficients and on the values of the areas of wear scars), while the geometry of the rubbing bodies, as well as the maximum Hertz stresses in the tribological contact, had a little effect on the antifriction and anti-wear characteristics of oils.

Enhancing tribological performance in PM Vanadis 6 steel through optimization of cryogenic and tempering treatment

Vanadis 6, which gained popularity for industrial applications due to increased strength and wear resistance, benefited from cryogenic treatment. This study investigated the influence of cryogenic and tempering treatments on the tribological properties of Vanadis 6 cold-work tool steel, crucial for cost-effective and durable tooling. Dry sliding wear experiments using Taguchi design under varying loads and sliding velocities revealed that cryogenic treatment at − 140 °C followed by 170 °C tempering resulted in the lowest wear rate, friction coefficient, smoothest worn surfaces, and the highest transition load. Microstructural analysis supported these findings, indicating reduced retained austenite and increased carbide count in cryogenically processed steel at − 140 °C.

Microstructure, hardness, and tribological performance of D2 tool steel fabricated by laser cladding using pulsed wave and substrate heating

D2 steel is a tool grade steel that presents hot cracking problems during the solidification process due to its alloying elements. On the other hand, additive manufacturing processes have great potential to manufacture, repair, and functionalize metal parts due to their low heat input, minimal distortion, and excellent metallurgical bonding. In this work, D2 metallic powder was deposited by the laser cladding process using pulsed wave, without and with preheating of the substrate. Through ANOVA statistical analysis using a complete factorial design 24, the optimal regions were determined to obtain D2 deposits with minimum dilution and depth, and maximum widths, heights and high hardness. Once the optimal parameters of the process were established, the coatings were deposited without and with preheating the substrate where, regardless of the condition, coatings without defects and good metallurgical adhesion were obtained. Coatings with preheating obtained higher cooling rates, where lower laser powers promoted higher rates; while in the coatings without preheating, lower duty functions promoted higher rates. The austenite, martensite and M7C3 eutectic carbides phases were obtained, with austenite being the main phase due to the C content in solid solution due to the cooling rates achieved. The coatings in as-built condition, reached hardness values between 606 and 711 HV (55–60 HRC), where the preheated coatings obtained the highest values. On the contrary, the coatings without preheating showed a better wear resistance (7.672 x10-6 mm3/Nm) due to the formation of tribo-layers due to the formation of oxides due to the higher amount of austenite.

Novel strategy for automated quality enhancement of up-facing inclined surfaces by incremental dual laser powder bed fusion

The low quality of up-facing inclined surfaces, combined with a lack of in-situ treatments, is a crucial challenge in Laser Powder Bed Fusion of metals. A recently proposed strategy, so-called Incremental Dual Laser Powder Bed Fusion (IDLPBF), aims to enhance the quality of up-facing inclined surfaces of metal parts directly during building. This is achieved through automatically alternating between laser remelting and building in height steps of 1.5 mm. Laser remelting involves selectively removing powder that is covering the inclined surface through nanosecond pulsed laser-induced shock waves and subsequently remelting the uncovered surface using a continuous wave laser. Treated surfaces are hence composed of laser remolten zones separated by elevated ridges in the overlap region, referred to as stitching zones. These stitching zones can compromise the geometrical accuracy and, consequently, pose a serious risk to fatigue performance. This work focuses on the enhancement of stitching zones and resulting quality of inclined surfaces through IDLPBF of a novel tool steel (M789). The paper covers the effect of various scan strategies for laser remelting on the stitching zone size. By optimizing the orientation of consecutive remelting passes and the position of the remelting fields, the stitching zone width could be reduced from 830 µm to 70 µm. Moreover, the optimized IDLPBF process was successfully applied to a large range of surface inclinations with respect to the horizontal build plate (5°-60°). For the first time, a significant quality improvement for 60° inclined surfaces was achieved, reducing the stress concentration factor by 35 %. The significantly reduced maximum stress concentrations were largely observed at stitching zones, in contrast to multiple high stress concentration sites randomly scattered across as-built surfaces. As a proof of concept, 60 mm high demonstrator parts including typically inaccessible surfaces located in the shadow zone were fully automated manufactured by IDLPBF.

Microstructure, Mechanical, and Corrosion Properties of 304 Stainless Steel-H13 Tool Steel Composite Cold Spray Coatings

Microstructure, Mechanical, and Corrosion Properties of 304 Stainless Steel-H13 Tool Steel Composite Cold Spray Coatings

Microstructural evaluation and mechanical properties of WC-6%Co/AISI 1045 steel joints brazed by copper, brass, and Ag-based filler metals: Selection of the filler material

Due to the higher production cost of the monolithic carbide tools as well as their brittle nature, cemented carbides such as WC-Co are frequently joined to tool steel. To overcome the joining complications that arise due to notable differences in thermal expansions between the components and the poor wettability, various investigators have used copper-based and silver-based filler metals to dissimilarly braze the cemented carbides to steels. However, researchers do not agree about the selection of filler material. This research investigates the use of pure copper, brass, and silver-based filler metals to join the WC-Co cemented carbide to AISI 1045 steel. In this regard, microstructural features and mechanical properties including microhardness and shear strength were studied. The results indicate the formation of Cu(Fe,Co) solid solution and η carbides at the joint interfaces as well as the development of various precipitated phases in the joint area comprising Fe-Zn and Co-Zn intermetallic compounds. The reaction layers at both sides of the joints accompanied by cobalt-depleted zone on the hard metal side were observed. While using the α−β brass interlayer, the increase in hardness of the joint area through the presence of (Cu,Zn) solid solution compared to pure copper, the joint shear strength was enhanced from 161 to 173 MPa. On the other hand, the utilization of silver-based filler alloy with a distribution of hard copper-rich solid solution phase (182 HV) embedded in a silver-rich ductile matrix (88 HV), presenting a dispersion hardening effect, improved the shear strength of the joint to 203 MPa.

Effect of Tempering on Structure and Properties of Plasma Surfacing of R2M9U High-Speed Tool Steel

Effect of Tempering on Structure and Properties of Plasma Surfacing of R2M9U High-Speed Tool Steel

Composition and Structure of the Surface Layers of Tool Steel after Laser Treatment

Composition and Structure of the Surface Layers of Tool Steel after Laser Treatment

CONTRIBUTION TO PRACTICAL ANALYSIS OF SURFACE ROUGHNESS MODELING DURING DRY HARD TURNING OF COLD WORK TOOL STEEL AISI D2

Quality of products is a major concern for hard machining industry aspects. However, the prediction of surface roughness in the function of the machining parameters is a targeted objective by the majority of researchers due to important industrial interest. This work is a contribution for developing comprehensive analyses of surface roughness models during dry hard turning of cold work steel AISI D2. It is focused on the treatment of predicted surface roughness values in correlation with cutting conditions such as cutting parameters (cutting speed, feed rate, and depth of cut), tools material, tool geometry, workpieces hardness, and machining times in order to establish of orientations for use which applied successfully in the industry from optimal selection of process variables. The approach consists in first conducting a literature survey through collecting and validating surface roughness models together with the corresponding material and also the cutting conditions. Then, results have been tabulated as to permit data mining treatment under data processing software which was developed. As a significant result, a strategic dashboard generating roughness data mining was made available to researchers and industrials. The optimums of parameters which condition the achievement of best machined surface qualities have been selected.

Implementation of Grey Wolf, Multi-Verse and Ant Lion Metaheuristic Algorithms for Optimizing Machinability of Dry CNC Turning of Annealed and Hardened UNIMAX® Tool Steel

Advances in machining technology and materials science impose the identification of optimal settings for process-related parameters to maintain high quality and process efficiency. Given the available resources, manufacturers should determine an advantageous process parameter range for their settings. In this work, the machinability of a special tool steel (UNIMAX® by Uddeholm, Sweden) under dry CNC turning is investigated. The working material is examined under two states; annealed and hardened. As major machinability indicators, main cutting force Fz (N) and mean surface roughness Ra (μm) were selected and studied under different values for the cutting conditions of cutting speed, feed rate, and depth of cut. A systematic experimental design was established as per the response surface methodology (RSM). The experimental design involved twenty base runs with eight cube points, four center points in the cube, six axial points, and two center points in the axial direction. Corresponding statistical analysis was based on analysis of variance and normal probability plots for residuals. Two regression models referring to main cutting force and surface roughness for both the annealed and hardened states of the material were developed and used as objective functions for subsequent evaluations by three modern meta-heuristics under the goal of machinability optimization, namely multi-objective grey wolf algorithm, multi-objective multi-verse algorithm and multi-objective ant lion algorithm. All algorithms were found capable of providing beneficial Pareto-optimal solutions for both main cutting force and surface roughness simultaneously whilst regression models achieved high correlation among input variables and optimization responses.

Experimental and statistical investigation of electro-erosion machining performance of cryogenic treated hardened AISI H13 hot work tool steel

This study investigated the machinability of AISI H13 hot work tool steel with a hardness of 54 HRC, which has been deep cryogenically treated using the electro-erosion machining technique, one of the unconventional manufacturing methods. The machinability parameters used in the study were determined as current (4, 8 and 12 A), pulse time (200, 300 and 400 µs) and three different electrodes (Copper, Graphite and Tuncop). The experimental design was designed according to the Taguchi L27 model, and machinability tests were carried out to examine the results obtained from the experimental study both experimentally and statistically. When the literature was examined, it was seen that cryogenic treatment was generally applied to electrode materials, and only surface roughness and material wear amounts were examined as output parameters. The original value of the study is the interpretation of the results by applying cryogenic treatment to the test material and exploring the surface roughness and material wear amount, as well as the hole diameters and criterion diameters formed on the treated surfaces after the EDM process. As a result of the study, it was observed that the surface roughness value, the hole diameter, the amount of material wear, and the crater diameter increased with the increase in ampere and impact time. The lowest surface roughness value was 2.266 µm in the graphite electrode material at 4 amps and 200 µs impact time and the highest wear amount was realized as 0.555 g in the copper electrode material 12 amps and 400 µs impact time. The smallest hole diameter was 12.254 mm with a tuncop electrode with a pulse duration of 4 amps and 200 µs, and the lowest crater diameter was 127.301 µm with a graphite electrode at a current of 4 amps and a pulse duration of 200 µs. When the signal-to-noise ratios were examined, the optimum machining parameters for surface roughness, hole diameter, material wear amount, and crater diameter were determined as A2B1C1, A1B3C3, A3B1C1, and A3B1C1, respectively. When the ANOVA results are examined, it is determined that the most effective parameter for the surface roughness is of the current value with 86.54%, the most effective parameter for the hole diameter is the electrode material with 85.20%, the most effective parameter for material wear amount is the electrode material with 45.67% and the most effective parameter for the crater diameter is current value with 75.35%.

The Influence of Q & T Heat Treatment on the Change of Tribological Properties of Powder Tool Steels ASP2017, ASP2055 and Their Comparison with Steel X153CrMoV12.

In connection with the growing importance of the efficiency and reliability of tools in industrial sectors, our research represents a key step in the effort to optimize production processes and increase their service life in real conditions. The study deals with the comparison of the tribological properties of three tool steels, two of which were produced by the powder metallurgy method-ASP2017 and ASP2055-and the last tool steel underwent the conventional production method-X153CrMoV12. The samples were mechanically machined with the finishing technology of turning and, finally, heat treated (Q + T). The study focused on the evaluation of hardness, resulting microstructure, wear resistance, and coefficient of friction (COF). The ball-on-disc method was chosen as part of the COF and wear resistance test. The tribological test took place at room temperature with dry friction to accelerate surface wear. The pressing material was a hardened steel ball G40 (DIN 100Cr6). Measurements were performed at loads of 10 N, 6 N, and 2 N and turning radii of 13 mm, 18 mm, and 23 mm, which represents a peripheral speed of 0.34, 0.47, and 0.60 m/s. The duration of the measurement for each sample was 20 min. The results showed that the COF of powder steels showed almost the same values, while a significant difference occurred with the increase of the radius rotation in the case of conventional steel. The results within the friction mechanism showed two types of wear, namely, adhesive and abrasive wear, depending on the Q + T process. From a tribological point of view in terms of wear, it was possible to state that the material ASP2055 after Q + T showed the lowest rate of wear of all the tested steels.

Effect of surface coating on fatigue life and fatigue crack growth behavior of AISI D2 tool steel

To study the effect of the specimen surface coating on the fatigue life and fatigue crack growth behavior, rotating bending fatigue tests were performed with a specimen coated with a TiCN thin film on AISI D2 tool steel (JIS SKD11) and a bare specimen without coating. Fatigue cracks developed inside the specimen because compressive residual stress was present on the surface of the coated and bare materials. The fatigue crack growth behavior of the internal cracks was investigated with the two-stage double-stress experimental method proposed by the authors. The fatigue life estimated from the fatigue crack growth (FCG) behavior of the internal cracks and the experimental results agreed. Furthermore, a method was proposed that can easily evaluate the effect of residual stress on fatigue life and FCG behavior. The evaluation and experimental results are in good agreement. In addition, the effects of atmospheric and vacuum conditions on FCG behavior are discussed.

Processing, microstructural characterization, and mechanical properties of deep cryogenically treated steels and alloys – overview

Abstract Deep cryogenic treatment (DCT), a technique of deep subzero processing, is utilized after quenching and well preceding tempering. In DCT, the materials are subjected to a soaking period of typically 24 h at a temperature of −196 °C. The optimal soaking period varies depending on the material to be cryotreated. The microstructural characteristics and mechanical properties of ferrous and nonferrous materials are significantly enhanced using DCT resulting in improved durability and functional performance of the mechanical components. The DCT is generally performed on tool steel, stainless steel, aluminum alloys, and magnesium alloys to improve its mechanical properties. The complete transition of residual austenite to martensite and finer secondary carbide precipitation correlates with an increase in the mechanical properties of tool steel. The nonferrous materials such as aluminum and magnesium alloys showed improved mechanical properties owing to the precipitation of finer second phases in the matrix. The main objective of this review paper is to provide an overview on the history and theories of DCT, important processing parameters, and the effect of DCT on microstructure and mechanical properties of tool steel, aluminum alloys, and magnesium alloys.

Evaluation of Microstructure and Hardness of AISI D2 Steel by Time Quenching in Comparison with Water and Oil Quenching

Due to an account of its excellent hardness and wear behavior, AISI D2 is used widely in producing of blanking and cold-forming dies, Punches, Shafts, Studs, and Bolts. Increasing toughness at a fixed high level of hardness is growing requirement for this kind of applications. Improving microstructure characteristics, especially carbides distribution by specific heat treatment, is an appropriate way to meet such requirement. The effect of quenching media on microstructure and hardness of pre-heated and austentized (at 980oC) AISI-D2 tool steel has been studied, and hardness and carbides morphology have been investigated. Three different medias, water, oil and water/oil (time quenching) have been used, then all samples were followed by the same tempering 350oC/1 hour. It has been found that the optimal carbides distribution and optimum hardness have been resulted from a time quenching method.

POSSIBILITY OF INCREASING THE LIFETIME OF THE CHOPPING KNIFE BY APPLICATION OF PVD COATING EVALUATED IN LABORATORY CONDITIONS

A wood is a heterogeneous material and its elements adversely affect the process of its processing. This also significantly affects the service life of tools during its processing. The aim of the contribution was, based on laboratory tests, to assess the suitability of the application of the selected coating on the chopping knife. After the basic analysis of the chopping knife, the CROSAL+ (AlCrN) coating was designed, which is an improved variant of the successfully used first generation CROSAL coating. In the experiment, samples from two knives made of tool steel X48CrMoV8-1-1 were analyzed. One sample was uncoated and the other coated. Based on the results of laboratory analyzes and tests, namely basic macroscopic and microscopic analysis of samples from tools, with semi-quantitative EDX analysis to determine the presence and content of individual chemical elements on the base material - substrate. Furthermore, the samples were tested for resistance to abrasive wear according to GOST 23.208-79. Relative resistance to abrasive wear ψabr was assessed. and hardness coefficient KT. HV and HRC hardness measurements were also carried out to determine the difference in hardness between uncoated and coated knife samples. In conclusion, it can be concluded that from the analysis and results of the measurements, the given coating for the process of processing wood by chopping can ensure the extension of the life of the tool and ensure the sufficient quality of the produced chips.