Die Steel Research Articles

Die steel design for additive manufacturing

A novel printable die steel was computationally designed and experiemtnally validated for selective laser melting (SLM), utilizing the advantages of the rapid solidification processes. During gas atomization, nanoscale TiN particles are intended to be insitu precipitated at 1790°C, nucleating δ-ferritic grains. Additionally, the chemical composition is adjusted to stabilize a complete δ-ferritic solidification via Scheil modeling to enhance the printability of the die steel. This work further introduces the concept of the matrix die steels aiming to dissolve solidification and primary carbides during solutionizing at a targeted temperature of 1100°C. Thus, the C-content is reduced to 1.4 mol.-% (0.3 wt.-%) compared to the benchmark H13 die steel with which contains 1.85 mol.-% (0.4 wt.-%). Even though a lower C-content is used, optimizing M2C driving force during tempering enables the die steel to achieve a peak hardness of 536 HV is achieved. Lastly, a superior thermal conductivity of 40 W m-1 K-1 is predicted at 450°C for the BCC matrix of the printable matrix die steel. The material design is based on thermo-chemical models interfaced with thermodynamic calculations as implemented in the Calculated Phase Diagram (CALPHAD) method.

Assessment of Recast Layer while Machining Die Steel D3 on EDM

The material melted and quickly solidified on the surface, forming a Recast layer over the machined surface. The present experimental assessment measures the extent of influence of machine variables towards the deposition of recast material post-machining Die Steel D3. The microstructure of the recast layer is dendritic and columnar due to sudden quenching, causing complex phase transformation. Scanning Electron Microscopy is utilized to assess the range of recast deposition. The range of average recast deposition is between 32.7 to 68.5 µm. The sequential model and lack of fit tests depict that the EDM parameters and recast layer can be modeled using 2FI equations. The analysis apprised that peak current (p-value < 0.0001) has a crucial impact on recast deposition. The duration (p-value = 0.4694) was the minimal affecting factor amid selected variables for white layer thickness, which aligns with the previous literature. The impact of current and duration is almost linear towards recast layer thickness and higher deposits of recast layer (RL) are observed at higher levels of current and duration. Lower RL can only be attained by setting a lower current and on duration. The influence of lower voltage is not much on recast layer thickness at minimum value of peak current. The residual error of 3.13% during model validation illustrates the adequacy of the model.

A Novel Design to Enhance the Tribological Properties of High‐Cr Hot Work Die Steel via Trace TiC Ceramic Nanoparticles

Excellent wear properties can improve the service performance and service life of high‐Cr hot work die steels. Herein, an innovative method is proposed to introduce TiC nanoparticles into the matrix of high‐Cr hot work die steels, and the effects of TiC nanoparticles on the microstructure and wear resistance of high‐Cr hot work die steels are investigated. In isothermal spheroidizing and quenching and tempering heat treatments, the TiC nanoparticles refine the granular pearlite, tempered martensite, and precipitates, which are attributed to the improved nucleation rates by increasing the number of heterogeneous cores. In sliding wear tests, the nanoparticle‐reinforced high‐Cr hot work die steels show higher wear resistance under the temperatures of 20 and 400 °C. The better wear properties of high‐Cr hot work die steels are because the substrates are strengthened and toughened, the dislocations are hindered, the mating areas are partially separated, and external loads are withstood by nanoparticles. This work shows new prospects for the development of high‐Cr hot work die steels with excellent wear performance.

Failure Analysis of Cryogenically Treated and Gas Nitrided Die Steel in Rotating Bending Fatigue

<div>AISI H13 hot work tool steel is commonly used for applications such as hot forging and hot extrusion in mechanical working operations that face thermal and mechanical stress fluctuations, leading to premature failures. Cryogenic treatment was applied for AISI H13 steel to improve the surface hardness and thereby fatigue resistance. This work involves failure analysis of H13 steel specimens subjected to cryogenic treatment and gas nitriding. The specimens were heated to 1020°C, oil quenched followed by double tempering at 550°C for 2 h, and subsequently, deep cryogenically treated at −185°C in the cryochamber. Gas nitriding was carried out for 24 h at 500°C for 200 μm case depth in NH<sub>3</sub> surroundings. The specimens were subjected to rotating bending fatigue at constant amplitude loading at room temperature. Measurement of surface roughness, hardness, and microstructural analysis indicated improved fatigue life for cryogenically treated specimens as compared to gas nitride, which could be attributed to fine carbide precipitation accountable for the delayed crack initiation and propagation.</div>

Temperature Field Simulation and Experimental Confirmation of Laser Cladding High-Entropy Alloy Coating on Cr12MoV

In order to meet the mechanical property of the die steel, this study used laser cladding to prepare a high-entropy alloy coating on Cr12MoV. A finite element method using a double ellipsoidal heat source model is proposed to simulate the evolution of the temperature field in laser cladding. The simulation results showed that with the increase in the power, the peak temperature of the molten pool increased from 2005.5 °C to 2357.4 °C, and the depth of the molten pool increased from 1.60 mm to 2.04 mm. The coating with the laser power of 1600 W had a good macroscopic quality and high lattice distortion (2.43 × 10−2). Due to the increase in laser energy density, the size of equiaxed crystals gradually increased from 1400 W to 1700 W. Under the comprehensive effect of the solution and fine grain strengthening, the coating with the power of 1600 W had a higher average microhardness (600 HV), which is 150% higher than that of the substrate. The experiment results further confirmed the accuracy of the simulation.

Decomposition behavior and evolution mechanism of MC primary carbonitride at 1473K and 1523K in die steel

Evolution of morphology and chemical composition and decomposition behavior of MC-type primary carbonitride held at 1473K and 1523K in H13 die steel are studied through electron probe microanalyzer (EPMA) and optical microscope (OM). Result shows that the decomposition of MC-type carbonitride has a relationship with constituent, holding temperature and time and carbonitride structure. It is found that Fe would diffuse to carbonitride from steel matrix accompanied by the decomposition of carbonitride at elevated temperature. The metastable (Vx,Mo1–x)(Cy,N1–y) is transformed into fine Fe-rich (Vx,Moz,Fe1–x–z)6(Cy,N1–y) when held at 1473K, and completely disappeared when held at 1523K. During isothermal holding, the mean size of carbonitride is gradually decreased to 6.5 μm, but there are still a small quantity of (Tix,V1–x)(Cy,N1–y) when held at 1253K for 15 h. Theoretical calculation indicates that Ti content in carbonitride is directly proportional to the thermal stability of carbonitride. As a result, the (Tix,V1–x)(Cy,N1–y) is transformed into (Tix,Vz,Fe1–x–z)(Cy,N1–y) with Fe content larger than 13 wt.% and becomes jagged at the edge. The compact (Tix,V1–x)(Cy,N1–y) is then evolved into the porous fishnet structure and finally dissolved as Fe larger than 32 wt.% in carbonitride. High temperature seems more beneficial for carbonitride decomposition than extension of holding time.

High temperature superlubricity behaviors achieved by AlSiN coatings against WS2 coatings at 600 °C

In this paper, AlSi coatings and AlSiN coatings on 22MB5 high strength steel and MoS2 coatings on the die steel were prepared by magnetron sputtering respectively. The tribological properties of the coatings were studied from room temperature to 800 °C. The hardness and the bond strength between the coatings and the substrate were also investigated. The experimental results show that AlSi coatings have poor anti-friction behaviors comparing with the steel, and coefficient of friction (CoF) is as 0.2 at room temperature, but 0.8 at 600 °C. The N element was doped into AlSi coatings with FeAl transition layers to improve the tribological performances of the coatings at high temperature. CoF of AlSiN coatings and H13 steel is high. However, AlSiN coatings have excellent wear-resistance. WS2 coatings were prepared on the surface of the die steel to improve high temperature anti-friction behaviors of AlSiN coatings and H13 steel pin. The experimental results show that WS2 coatings exhibit good high temperature anti-friction behaviors. Super low friction about 0.003 is achieved at 600 °C. High temperature superlubricity mechanisms of AlSiN coatings and WS2 coatings are discussed systematically.

Frictional Wear and Thermal Fatigue Properties of Die Steel after Ultrasound-Assisted Alloying

The surface layer of 8407 die steel was strengthened using the combination of ultrasonic surface rolling and high-energy ion implanting in the present work. The strengthened layer was then characterized via microstructure observation, composition analysis, and hardness test. After that, the frictional wear and thermal fatigue properties of high-energy ion implanting specimens and composite-reinforced specimens were compared. Results show that the pretreatment of specimens with ultrasonic surface rolling causes grain refinement in the material surface, which promotes the strengthening effect of high-energy ion implanting. The wear volume of composite-reinforced specimens at medium and high frequencies is reduced by about 20%, and the wear resistance of these specimens is significantly improved with a lower friction coefficient and wear volume at moderate and high frequencies in alternating load friction experiments. Meanwhile, the thermal fatigue crack depth of composite-reinforced specimens is reduced by about 47.5%, which effectively prevents the growth of thermal cracks in the surface, thus improving the curing ability of the implanted elements. Therefore, composite strengthening of the mold steel surface is conducive to improving the cycle life, ensuring accuracy, effectively hindering the expansion of thermal cracks, and saving the cost of production.

Preservation conditions of hot work hardening in die steel with regulated austenitic transformation during exploitation

Die steels with regulated austenitic transformation during exploitation (RATE steels) are a new class of tungsten-free steels for hot forming at operating temperatures up to 750 – 800 °C. High durability of the pressing tool and its long service life are ensured by the ability of these steels to preservation of hot work hardening. This circumstance distinguishes RATE steels from traditional alloy steels, which are prone to softening at high temperatures. However, the temperature ranges for the preservation of hot hardening in RATE steels was not systematically studied, which makes it difficult to use a pressing tool more efficiently. In this paper, we study the mechanical behavior of RATE die steel during thermo-mechanical treatment in a wide temperature range, including the stage of preliminary deformation at lower temperatures and the stage of main deformation at higher temperatures corresponding to operating temperatures of the pressing tool. The thermo-mechanical treatment was carried out using a hardening-deformation dilatometer DIL 805 A/D according to the compression mode. We obtained the true stress-strain curves and determined the mechanical characteristics and strain hardening index. Size of the former austenite grain in the steel structure after thermo-mechanical treatment was measured. The temperature-force conditions for enhancing hot hardening or stabilizing hot hardening, or softening, were established. It is shown that the hardening achieved at the stage of preliminary deformation at a temperature of 450 °C is enhanced at the stage of main deformation at temperatures in the range from 550 to 800 °C, while in this temperature range the tendency to increase hot hardening is weakened.

Development Trend in Composition Optimization, Microstructure Manipulation, and Strengthening Methods of Die Steels under Lightweight and Integrated Die Casting.

In the general environment of lightweight automobiles, the integrated die-casting technology proposed by Tesla has become the general mode to better achieve weight reduction in automobiles. The die-casting mold required by integrated die-casting technology has the characteristics of large scale and complexity. Hence, higher requirements are put forward for the comprehensive performance of the die steel. Despite the stagnation in the progress of conventional strengthening methods, enhancing the performance of die steel has become increasingly challenging. Indeed, it necessitates exploring novel die steel and optimizing heat treatment and reinforcement technologies. This article summarizes and analyzes the development status of die steel and corresponding heat treatment and microstructure manipulation as well as strengthening methods and elaborates on an excellent nano-strengthening technology. Furthermore, this review will aid researchers in establishing a comprehensive understanding of the development status of die steel and the processes utilized for its strengthening. It will also assist them in developing die steel with improved comprehensive performance to meet the high demand for mold steel in the integrated die-casting technology of the new era.

Numerical Simulation of Thermal Field and Performance Study on H13 Die Steel-Based Wire Arc Additive Manufacturing

In order to explore the relationship between welding thermal cycles and the thermal field during the repair process of dies, a numerical simulation software (SYSWELD) was employed to construct a thermo-mechanical coupled model. The influence of various inter-layer cooling times was investigated on heat accumulation, residual stress, and deformation of the repaired component. The results showed that the numerical simulation results agreed well with experimental data. The temperature within the cladding layer gradually rose as the number of weld beads increased, leading to a more pronounced accumulation of heat. The residual stress exhibited a double-peak profile, where the deformation of the repaired component was large at both ends but small in the middle. The less heat was accumulated in the cladding layer with a prolonged cooling time. Meanwhile, the residual stress and deformation in the repaired component experienced a gradual decrease in magnitude. The numerical simulation results demonstrated that the microstructure of the repaired component predominantly consisted of martensite and residual austenite at the optimal cooling time (300 s). Furthermore, the microhardness and wear resistance of the cladding zone significantly surpassed those of the substrate. In conclusion, this study suggested the prolonged cooling time mitigated heat accumulation, residual stress, and deformation in repaired components, which provided a new direction for future research on the die steel repairments.

Numerical and Experimental Investigation of Solidification Structure and Macrosegregation in Continuously Cast 2311 Die Steel Slab

Numerical and Experimental Investigation of Solidification Structure and Macrosegregation in Continuously Cast 2311 Die Steel Slab

Effect on Surface Properties of H13 Mold Steel Cladding Layer by Scanning Strategy

Laser cladding technology is used to clad the surface layer of H13 mold steel with Ni60A metal powder coating to solve the failure problem. The study used JMatPro software to extract and fit the thermophysical property parameters of the substrate and the clad material, and then used ANSYS APDL software to qualitatively analyze the distribution of melt pool morphology, nodal temperature versus time course curve and residual stress magnitude during the laser cladding process. Based on the results of the minimum residual stress in the cladding, reasonable scan paths were derived for the preparation of metal coatings on the surface layer of the die steel. The results show that the maximum peak temperature of the cladding process is 2515°C using short path scanning. The cladding layer can form a good metallurgical bond with the substrate at this temperature, with a stress of 406.68 MPa in the scanning direction and 284.45 MPa perpendicular to the scanning direction, which is significantly smaller than the residual stresses of other scanning methods. The residual stress values for the different strategies are from largest to smallest: spiral scan > block scan > long path scan > short path scan.

Friction Behavior and Self-Lubricating Mechanism of SLD-MAGIC Cold Worked Die Steel during Different Wear Conditions

Wear tends to shorten tool life, reduce component quality. To prevent or postpone the wear of tool steel forming tools, methods to increase wear resistance, such as increasing the material hardness, optimizing the carbide distribution and application of surface coatings, are often used. However, the formation of lubricating phases in steels leading to anti-attrition is less investigated. The friction behavior of three steels were investigated thoroughly by a tribo test with different normal loads. A Field-emission scanning electron microscope (FE-SEM) along with energy dispersive X-ray spectroscopy (EDS) were used to characterize the microstructure as well as the influence of the precipitated phases on the wear mechanisms. Results showed the friction coefficient decreased with increasing normal load, whereas the wear rate increased with increasing normal load. Compared with SKD11 and DC53 steels, the friction coefficient and wear volume of SLD-MAGIC steel were reduced by 0.1 to 0.3 and 10% to 30%, respectively. With the increase of normal load, the wear mechanism changed in order from abrasive wear, adhesive wear to oxidation wear. The more carbide contents, the rounder the carbide, the better the wear resistance of the tool steel. It can be shown that, under different normal loads, SLD-MAGIC exhibits better wear performance than SKD11 and DC53 tool steels, which is mainly due to the self-lubricating phenomenon of SLD-MAGIC steel. The self-lubricating mechanism was due to the fact that the exfoliated sulfide during wear formed a lubricating film to reduce wear.

Microstructure and Mechanical Properties of Gradient Interfaces in Wire Arc Additive Remanufacturing of Hot Forging Die Steel

Hot forging dies are subjected to periodic thermal stress and often fail in the forms of thermal fatigue, wear, plastic deformation, and fracture. A gradient multi-material wire arc additive remanufacturing method for hot forging dies was proposed to extend the service life of hot forging dies and reduce total production costs. The properties of multi-material gradient interfaces play a critical role in determining the overall performance of the final products. In this study, the remanufacturing zone of a hot forging die was divided into three deposition layers: the transition layer, the intermediate layer, and the strengthening layer. Experiments of wire arc additive manufacturing with gradient material were conducted on a 5CrNiMo hot forging die steel. The microstructure, microhardness, bonding strength, and impact property of gradient interfaces were characterized and analyzed. The results revealed that the gradient additive layers and their interfaces were defect-free and that the gradient interfaces had obtained a high-strength metallurgical bonding. The microstructure of the gradient additive layers presented a gradient transformation process of bainite-to-martensite from the bottom to the top layer. The microhardness gradually increased from the substrate layer to the surface-strengthening layer, forming a three-level gradient in the range of 100 HV. The impact toughness values of the three interfaces were 46.15 J/cm2, 54.96 J/cm2, and 22.53 J/cm2, and the impact fracture morphology ranged from ductile fracture to quasi-cleavage fracture. The mechanical properties of the gradient interfaces showed a gradient increase in hardness and strength, and a gradient decrease in toughness. The practical application of hot forging die remanufactured by the proposed method had an increase of 37.5% in average lifespan, which provided scientific support for the engineering application of the gradient multi-material wire arc additive remanufacturing of hot forging dies.

Design and analysis of punch and die combination for fabrication of tractor fender using FEM

In the current times, most of the manufacturers are focussed on technology assisted optimization of resources, pertaining to capital investment in consonance with higher production rates with lowest minimum defects in the output produced. In agreement with the same, the present research identifies the designing characteristics of punch and die arrangement; meant for securing high degree of production outcomes associated with manufacturing of tractor fender component (side part) as part of press tool exercise. Moreover, the aforementioned line of action is adopted to achieve minimum time cycle for production as well as for minimising die material used by involving two different die blocks; unlike previous approach of adopting a die plate combination. The novel approach led to significant decrement in die steel consumption and material cost as well. The CAD model of punch and die arrangement has been developed on Catia Software whereas; the structural analysis has been accomplished by Ansys software. Besides that, this scheme also develops a comprehensive picture of punching through mathematical calculation of all the die parts and detailed analysis of same by way of finite element analysis. The die was specifically designed and manufactured at the establishment of Indofarm Equipments Private Limited, Baddi (Himachal Pradesh).

Study of Material Removal Rate Process Parameter in WEDM

Wire cut Electrical Discharge Machining is known as nontraditional machining process. It has broad application in complex part or geometry machining. It is known as a non-contact process. The main objective of this research work is to investigate the influence of process parameters of Wire cut Electrical-Discharge Machining in material removal rate. Die steel D3 has been selected as workpiece material for study. The process parameters are peak current, pulse on time and wire tension. In experimental analysis it was concluded that on MRR the most influential process parameter is peak current with contribution of 86.02 %. Pulse of time has 12.29 % contribution and wire tension has minimum contribution of 1.12 % with 0.57% error in the study.

Проблемы исследования остаточных напряжений в упрочненном поверхностном слое инструментальных штамповых сталей после диффузионного бороалитирования

Introduction. Diffusion boroaluminizing provides improved performance properties of the die steels’ surface such as wear resistance, high hardness, and corrosion resistance. Surface hardening can significantly contribute to the occurrence of technological residual stresses (TRS) on the surface. Currently, there are no studies on the topic of the stress state of diffusion boroaluminizing. The purpose of this work is to develop a method for determining the TRS and a nature of its distribution in the diffusion layers on the surface of 5CrNiMo and 3Cr2W8V die steels after boroaluminizing by a mechanical method. The paper considers the results of experimental studies on the determination of the normal components of TRS by the mechanical method in diffusion layers of die steels. The conducted studies showed that the formation of unfavorable tensile TRS occurs along the depth of the hardened layer in the case of the investigated TCT method and types of steels. Results and discussions. The main approaches for determining the TRS in the surface layer of 3Cr2W8V and 5CrNiMo die steels after TCT are considered. Problems in the determination of TRS by the mechanical method on the UDINON-2 unit are identified, and its solution is proposed. The efficiency of using the anodic dissolution method for the continuous removal of stressed layers during the TRS study by the mechanical method on the UDION-2 unit is shown. The optimal electrolyte composition is selected for the process of anodic dissolution consisting of: NaNO3 – 60 g/l; NaNO2 – 5 g/l; Na2CO3 – 5 g/l; C3H8O3 – 15 g/l; H2O – the rest. The distributions of the normal TRS components in the diffusion layer of die steel specimens are revealed. It is established that, during the TCT of these steels predominantly tensile TRS are formed in the surface layer. Further research will be aimed at developing measures to reduce tensile TRS during diffusion boroaluminizing of die steels.

Investigation and Prediction of ECMM characteristics of Hardened Die Steel with Nanoparticle Added Electrolytes Using Hybrid Deep Neural Network

Abstract In our work, the process efficiency of the ECMM should be improved by using different combinations of nano-particles and added electrolytes. The superior aim of this work is to improve and predict the ECMM machining characteristics of die hardened steel, namely material removal rate (MRR), Tool wear rate (TWR) and Surface Roughness (Ra). The machining conditions are optimized using Response Surface Methodology (RSM) based on Box Behnken Design. The better Nano electrolyte is optimized using Deer Hunting Optimization (DHO) based on the machined outcomes, and the performances are predicted using a hybrid Deep Neural Network (DNN) based DHO. The hybrid DNN-DHO based predicted outcome of MRR is 0.361 mg/min, TWR is 0.272 mg/min and Ra is 2.511 μm. The validation results show that our proposed DNN-DHO model performed well and obtained above 0.99 regression for both training and validation of DNN-DHO, where the root mean square error ranges between 0.018 and 0.024.

Inductively coupled plasma etching of bulk tungsten for MEMS applications

As a promising material for bulk micromachining for MEMS applications, tungsten can be used as microneedles for medicine injection and tools for micro-inject molding, ultrasonic machining, and electrical discharge machining. However, it is difficult to fabricate microstructures with high aspect ratios and small feature sizes due to the excellent material of tungsten properties, such as chemical stability, high hardness, and high melting point. Here, an inductively coupled plasma (ICP) deep etching process is developed for bulk tungsten, and its process parameters are studied. After optimizing the process parameters, three recipes were developed for different MEMS applications. A patterned tungsten structure with a depth of more than 300 µm was etched by tungsten (W) ICP deep etching (WIDE) at an etch rate of 2.73 µm/min and etch selectivity of 35. The WIDE process produced a tungsten microstructure with a high aspect ratio (> 20), a small feature size (< 3 µm), and a surface roughness of Ra 30 nm. To demonstrate the potential application prospect of deep etching bulk of tungsten, tungsten microneedles with a positive sidewall angle and several non-silicon substrates for MEMS applications were achieved based on the WIDE process. • Bulk tungsten ICP deep etching process development based SF 6 +O 2 +C 4 F 8 . • Effect of process parameters on ER, ES, DUR, roughness, sidewall angle. • μ-structures with > 300 µm deep, > 20 AR, and Ra 30 nm roughness. • Die steel, glass, and polymer μ-structures machined by etched tungsten. • Metal-based and non-silicon-based MEMS application prospect.