Search Results (58)

The quality of laser cladding is strongly influenced by process parameters, which interact in complex and often nonlinear ways. The existing literature primarily focuses on the influence of process parameters on surface properties. However, limited research has explored the relationship between process parameters, surface properties, and their optimization. To bridge this gap, this study introduces a novel parameter modeling and optimization approach using the Catch Fish Optimization Algorithm (CFOA). Key process parameters, including laser power, scanning speed, and powder feeding rate, were systematically analyzed for their effects on the surface quality of H13 die steel. An orthogonal experimental design was employed to develop a regression model capable of accurately predicting cladding quality metrics, such as dilution rate, microhardness, and aspect ratio. To address the multi-objective nature of the optimization problem, the analytic hierarchy process (AHP) was used to transform it into a single-objective framework. The proposed approach identified an optimal parameter combination: laser power of 1628.19 W, scanning speed of 9.9 mm/s, and powder feeding rate of 14.73 g/min. Experimental validation demonstrated significant improvements in cladding performance, with enhancements of 19.71% in dilution rate, 3.37% in microhardness, and 28.66% in aspect ratio. The CFOA also shows global search capabilities and precision compared to conventional methods, making it a robust tool for complex optimization tasks. This study presents an innovative methodology for optimizing laser cladding processes, providing effective H13 die steel repair solutions. It also emphasizes the versatility of metaheuristic algorithms for advancing manufacturing process optimization. Full article

This study addresses the crack formation problem when laser cladding CoCrFeNiAl high-entropy alloy onto H13 hot-work die steel, aiming to identify suitable transition layer materials. Five nickel-based alloys—Inconel 718, Inconel 625, Hastelloy X, FGH4096, and FGH4169—are selected as alternatives. Three-point bending and hot tensile tests are conducted to assess performance under different stress directions. Test results show that the FGH4096 and FGH4169 coatings fail due to insufficient element diffusion and weak interfacial bonding. Cracks appear at the coating–substrate interface of Inconel 625 and Hastelloy X. In contrast, Inconel 718 performs best, with excellent thermal expansion matching and strong stress resistance. In the three-point bending test, the specimens with Inconel 718 transition layers did not show cracks during the loading process, while specimens with some other alloy transition layers cracked or fractured, which proves that Inconel 718 can effectively enhance the bonding force between the coating and the substrate and improve the material’s performance under bending stress. In the hot tensile test, the stress–strain curve of Inconel 718 is at a high position with a high yield strength, showing excellent resistance to plastic deformation and significantly improving the performance of the nickel-based layer under hot tensile conditions. Therefore, Inconel 718 is identified as the optimal transition layer material. Full article

In hard milling, there has been a significant surge in demand for sustainable machining techniques. Research indicates that the Minimum Quantity Lubrication (MQL) method is a promising approach to achieving sustainability in milling processes due to its eco-friendly characteristics, as well as its cost-effectiveness and improved cooling efficiency compared to conventional flood cooling. This study investigates the end milling of AISI H11 die steel, utilizing a cooling system that involves a mixture of graphene nanoparticles (Gnps) and sesame oil for MQL. The experimental framework is based on a Taguchi L36 orthogonal array, with key parameters including feed rate, cutting speed, cooling condition, and air pressure. The resulting outcomes for cutting zone temperature and surface roughness were analyzed using the Taguchi Signal-to-Noise ratio and Analysis of Variance (ANOVA). Additionally, an Adaptive Neuro-Fuzzy Inference System (ANFIS) prediction model was developed to assess the impact of process parameters on cutting temperature and surface quality. The optimal cutting parameters were found to be a cutting speed of 40 m/min, a feed rate of 0.01 mm/rev, a jet pressure of 4 bar, and a nano-based MQL cooling environment. The adoption of these optimal parameters resulted in a substantial 62.5% reduction in cutting temperature and a 68.6% decrease in surface roughness. Furthermore, the ANFIS models demonstrated high accuracy, with 97.4% accuracy in predicting cutting temperature and 92.6% accuracy in predicting surface roughness, highlighting their effectiveness in providing precise forecasts for the machining process. Full article

Conformal cooling channels have demonstrated significant advantages for cast parts and 3D-printed moulds in the high-pressure die casting (HPDC) process. However, the complex geometry of moulds, characterised by small intrusions, sharp corners, and fins, often results in nonuniform cooling in certain regions, leading to overcooling or overheating. This study proposes integrating lattice structures within specific regions of 3D-printed moulds or inserts as an additional control parameter to enhance cooling uniformity by increasing thermal resistance in targeted areas. A validated three-dimensional Computational Fluid Dynamics (CFD) model was employed to incorporate three types of lattice structures, aiming to limit local heat flux in overcooled areas. The model specifically addresses the cooling of an aluminium alloy profile with 90-degree-angled corners, using H13 steel mould properties. The results indicate that implementing a lattice structure as a sleeve around the cooling pipe at the corner two sides improved temperature uniformity by over 42%. However, this increased thermal resistance also led to a 16 °C rise in corner temperature. These findings suggest that implementing lattice structures in the mould can improve cooling uniformity. However, they should be positioned away from the thickest regions of the mould to avoid increasing the modelling time. Full article

The article addresses stress formation in the structural 3D-printed elements of a high-pressure die casting die mould used for production of aluminum castings. The 3D-printed elements with conformal cooling are manufactured of 18Ni300 powder. Initial numerical calculations were performed on a test die mould made of standard steel X40CrMoV5 to determine temperature distribution and stress state, providing a baseline for comparing 3D-printed 18Ni300 parts. A database for 18Ni300 material was developed, including optimal heat treatment parameters: aged at 560 °C for 8 h. The resulting tensile strength of approximately ~1600 MPa, yield strength 1550 MPa, and elongation 6–7%, with properties temperature-dependent from 20 °C to 600 °C. Results show that conformal cooling increases stress gradients, highlighting the demands on fatigue strength at elevated temperatures. The study revealed that the heat treatment significantly influences the final properties, with tensile strengths of 1400–2000 MPa and elongation from 1 to 8%. While the heat treatment has a greater impact on the mechanical properties than the printing parameters, optimizing the printing settings remains crucial for ensuring density and quality in the die moulds under cyclic loads. Full article

The Ostergren model is simple in form and widely used in engineering practice, also serving as the modeling basis of both the damage differentiation and crack propagation models. However, the shortcomings of the Ostergren model are that the modeling process is affected by thermomechanical fatigue (TMF) test parameters. To establish a TMF life normalized model, a modified Ostergren model based on hysteresis energy damage and TMF data for H13 steel was proposed. The model was successfully applied to TMF life prediction for 4Cr5Mo2V steel. The band of predicted life and test life is basically within the factor of 1.5. In summary, the modified Ostergren model is suitable for the TMF life prediction of Cr-Mo-V-type die-casting die steel. Full article

Nowadays, H13 hot work steel is a commonly used hot work die material in the industry; however, its creep behavior for additively manufactured H13 steel parts has not been widely investigated. This research paper examines the impact of volumetric energy density (VED), a critical parameter in additive manufacturing (AM), and the effect of post heat-treatment nitrification on the creep behavior of H13 hot work tool steel, which is constructed through selective laser melting (SLM), which is a powder bed fusion process according to ISO/ASTM 52900:2021. The study utilizes nanoindentation tests to investigate the creep response and the associated parameters such as the steady-state creep strain rate. Measurements and observations taken during the holding phase offer a valuable understanding of the behavior of the studied material. The findings of this study highlight a substantial influence of both VED and nitrification on several factors including hardness, modulus of elasticity, indentation depth, and creep displacement. Interestingly, the creep strain rate appears to be largely unaltered by these parameters. The study concludes with the observation that the creep stress exponent (n) shows a decreasing trend with an increase in VED and the application of nitrification treatment. Full article

Nowadays, powder-based manufacturing processes are recognized as cost-efficient methods frequently employed for producing parts with intricate shapes and tight tolerances in large quantities. However, like any manufacturing method, powder-based technologies also have several disadvantages. One of the most significant issues lies in the degree of porosity. By modifying the morphology of the gas-atomized spherical 17-4PH stainless steel powder via prior ball milling and then raising both the pressure of cold compaction (1.6 GPa) and sintering temperature (1275 °C), the porosity could be reduced considerably. In our novel powder metallurgical (PM) experimental process, an exceptionally high green density of 92% could be reached by employing die wall lubrication instead of internal lubrication and utilizing induction heating for rapid sintering. After sintering (at temperatures of 1200, 1250, and 1275 °C), the samples aged in the H900 condition were then mechanically tested (Charpy impact, HV hardness, and tensile tests) as a function of porosity. Sintering at 1275 °C for one hour enabled porosity reduction to below 4%, resulting in 1200 MPa yield strength and 1350 MPa ultimate tensile strength with significant (16%) fracture strain. These values are comparable to those of the same alloy products fabricated via ingot metallurgy (IM) or additive manufacturing (AM). Full article

Surface modification through electrical discharge machining (EDM) results in many advantages, such as improved surface hardness, enhanced wear resistance, and better micro-structuring. During EDM-based surface modification, either the eroding tool electrode or a powder-mixed dielectric can be utilized to add material onto the machined surface of the workpiece. The current study looks at the surface modification of H13 die steel using EDM in a dielectric medium mixed with graphite powder. The experiments were carried out using a Taguchi experimental design. In this work, peak current, pulse-on time, and powder concentration are taken into consideration as input factors. Tool wear rate (TWR), material removal rate (MRR), and the microhardness of the surface of the machined specimen are taken as output parameters. The machined surface’s microhardness was found to have improved by 159%. The results of X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS) analysis and changes in MRR and TWR due to the powder-mixed dielectric are also discussed in detail. Full article

Using 3D scanning, coordinate measuring machine, and roughness measurements we evaluated and compared zinc alloy castings produced in conventionally and additively manufactured shaped mould parts. Tests were conducted on castings from new shaped parts and subsequently after approximately every 100,000 shots. Castings from conventional parts had higher dimensional stability, but both types showed decreasing dimensional deviations over time. Castings from new additively manufactured parts had higher roughness initially, but this improved with use. Overall, there were no significant issues, and the benefits of additive-shaped parts prevailed. However, more testing is needed for a final recommendation for use in real operating conditions, requiring hundreds of thousands more shots. Full article

The evolution of MC-type primary carbonitrides (M=V, Ti, Mo; C=C, N) in terms of morphology, quantity, size and composition was systematically investigated in commercial H13 die steels with different Ti and N contents during thermal holding at 1250 °C for 5 h to 15 h. Results showed that the mean size and quantity of carbonitrides in the four samples had decreased during thermal holding. However, the mean size and quantity of MC carbonitrides had increased with increasing Ti contents when held at 1250 °C while the addition of N increased the quantity but decreased the sizes of the stable MC carbonitrides. It was concluded that the compact carbonitrides could be decomposed and changed into a fishnet structure when held at 1250 °C, especially in samples #1 and #2 containing lower Ti and N contents. The decomposition mechanism was illustrated considering the changes in Ti and Fe elements in carbonitrides. On the basis of the thermodynamic model, the thermal stability of (Ti_x,V_1−x)(C_y,N_1−y), with a larger x value, in samples #3 and #4 containing more Ti and N contents was generally higher than those in samples #1 and #2. To control the Ti-containing MC carbonitrides, the low Ti and N contents and high holding temperature should be taken into consideration. Full article

Co-based alloys are promising alternatives to replace the currently used tool steels in aluminum die-casting molds for producing sophisticated products. Although the reaction is significantly less severe compared to that of tool steels, bare Co-29Cr-6Mo (CCM) alloy is still gradually corroded under molten Al, leading to the local failure of the alloy due to the formation of intermetallic compounds between the matrix and molten Al. This study indicated that prior oxidation treatment at 750 °C on CCM alloy is beneficial in enhancing the corrosion resistance of the alloy to molten Al. The is more pronounced in the alloy after a longer oxidation treatment. However, after oxidation for longer than 24 h, the protectiveness of the film cannot be enhanced anymore. In addition, even after the full failure of the oxide film, the thickness loss rate of a sample with prior oxidation treatment is much lower than that of a bare sample. This can be attributed to the fact that network-aligned oxide particles of the cone structure boundary inhibit both the outwards movements of alloying elements and the dissolution of the intermetallic layer. Full article

Plasma nitriding, a surface treatment technique, is gaining popularity, as it is environment-friendly and offers superior mechanical properties. This research studied the wear and friction performance of AISI H13 die steel after plasma nitriding in a gas mixture of N2:H2 at 20:80, 50:50, and 80:20 (volume ratio) at a fixed time and temperature. This work aimed to analyze the sliding wear performance of the plasma-nitrided tool die steel in hot-forming operations at higher loads. Scanning electron microscopy/electron-dispersive spectroscopy (SEM/EDS) and X-ray diffraction (XRD) techniques were used to study the microstructures of the H13 die steel pins after plasma nitriding. Wear tests were performed on a high-temperature tribometer under uni-directional sliding and dry conditions using a high-temperature tribometer under a 50 N load at various operating temperatures ranging from 25 °C to 600 °C. The results show that the plasma-nitriding process with N₂:H₂ at 20:80 improved the wear behavior of H13 steel. The friction coefficients and wear volume losses for all the plasma-nitrided specimens were less than those of the untreated die steel. Full article

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. Full article

To repair or improve the performance of H13 hot working molds through the additive manufacturing process, IN 718 was coated on H13 die steel by high-speed laser cladding followed by an ultrasonic surface rolling process (USRP). The mechanism of ultrasonic surface rolling on the mechanical properties of the coating was studied. After USRP, the coating exhibited severe plastic deformation; the microscopic organization of the surface layer was refined and the particle size was significantly reduced. The violent plastic deformation of the coating caused by USRP improved the dislocation density and the grain boundary density, providing an improved yield strength of the coating and improving the high-temperature wear resistance of the coating. After USRP, the surface hardness of the coating increased by 30%. Compared with the coating without USRP, the wear resistance of the coating greatly improved; the wear rate was reduced by 51% and the wear mechanism of the coating changed from large-area adhesive wear and severe abrasive wear to small-area adhesive wear and slight abrasive wear. The IN 718 coating after USRP had a higher hardness and greater wear resistance, significantly improving the service life of H13 steel. Full article