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Proceedings Papers
IFHTSE2024, IFHTSE 2024: Proceedings of the 29th International Federation for Heat Treatment and Surface Engineering World Congress, 16-22, September 30–October 3, 2024,
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Metal additive manufacturing is a molding method with a high degree of freedom because it can be created from high-strength materials using by CAD, etc. In recent years, there is a demand for metal additive manufacturing due to the demand for more complex mechanisms and shape in industrial products. However, the mechanical properties of metal additive manufacturing materials as metallic materials are not clear compared to metallic materials by melting method. In this study, two types of metal additive manufacturing (AM) materials with different lamination directions are carburized and heat treated to clarify the differences from general metallic materials and to clarify the causes. The carburized AM materials were confirmed to have a surface hardness of 550HV and a total carburization depth of 200 μm, but the amount of carburization differed depending on the orientation. In addition, when analyzed with a SEM, a metal structure was formed in an equiaxed crystal shape, and segregation of metal elements was observed.
Proceedings Papers
IFHTSE2024, IFHTSE 2024: Proceedings of the 29th International Federation for Heat Treatment and Surface Engineering World Congress, 23-28, September 30–October 3, 2024,
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It is well known that the maximum prior austenite grain size after carburizing heat treatment is approximately positively correlated with the maximum shear strain in the case of simple deformation of pre process as cold working treatment. On the other hand, it is generally known that the maximum shear strain and the maximum grain size do not correspond when complex cold working is performed, but the reason of these phenomena is not well known. Then, it is necessary to investigate the relationship between the applied strain during cold working with multiple steps and prior austenite grain size after heat treatment(GG). In this study, we used a processing method called HPT processing, which introduces shear strain by torsion deformation under applying high hydrostatic pressure to the top and bottom of a disk-shaped sample using a die, and investigated how GG changes due to the accumulation of dislocations by focusing on the strain amount | ± Δ ε| given in one pass controlled by a processing path called Cyclic-HPT (c-HPT) (4) and the total strain amount 𝛴| ± Δ ε| given to the sample by the accumulation of one pass. As a result, when finer strain is applied, the grain size does not necessarily become smaller, but rather there are boundary conditions that indicate the positive and negative grain size with respect to the number of strains. Similarly, for the grain size distribution, an increase and decrease in grain size was observed with respect to radial distance, so there are boundary conditions that indicate the positive and negative grain size with respect to distance. From these results, it is believed that this may be the mechanism for grain growth behavior in the case of cold working, which involves complex deformation.
Proceedings Papers
IFHTSE2024, IFHTSE 2024: Proceedings of the 29th International Federation for Heat Treatment and Surface Engineering World Congress, 89-96, September 30–October 3, 2024,
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Diamond-like carbon (DLC) coatings, which improve wear resistance and extend component service life, have gained considerable research attention as an approach for conserving limited resources. The DLC coating is a highly functional film with high hardness and excellent low-friction, wear-resistance, and corrosion-resistance properties; however, it has high residual stress and low adhesion between the substrate and the film. Existing studies have focused on using DLC containing metallic elements (Me-DLC) as an intermediate layer to minimize residual stress, thereby improving adhesion. Si-DLC is deposited using a mixture of hydrocarbon gases, such as methane (CH 4 ) and acetylene (C 2 H 2 ), and silicon gases, such as tetramethylsilane (TMS: Si(CH 3 ) 4 ), H, and Si, to form the DLC coating. The composition, hardness, Young’s modulus, and friction coefficient of the film can be controlled by changing the composition of the gas mixture. This study investigated the effect of the flow rate ratio of source gases (CH 4 and TMS; C 2 H 2 and TMS) on the properties of the DLC film when Si-DLC is deposited as an intermediate layer on austenitic stainless steel SUS304 using plasma-enhanced chemical vapor deposition. The coating time was adjusted to ensure that the thicknesses of the Si-DLC layer and DLC film were 1.0 and 0.2 μm, respectively, under both conditions. The results demonstrated that the durability of the DLC film improved and adhesion decreased with a decrease in the TMS ratio in the Si-DLC intermediate layer. Durability improved and adhesion decreased when C 2 H 2 was used as the source gas, as compared to when CH 4 was used.
Proceedings Papers
IFHTSE2024, IFHTSE 2024: Proceedings of the 29th International Federation for Heat Treatment and Surface Engineering World Congress, 97-106, September 30–October 3, 2024,
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High-entropy alloys (HEA) are multinary alloys obtained by blending at least five metallic elements in compositions close to their isoatomic fractions (5–35 at%). Generally, HEAs are produced by arc melting and casting. However, the cast specimens undergo phase separation and have a non-uniform microstructure. In contrast to ingot metallurgy, powder metallurgy has several advantages such as the possibility of alloying metals with high melting points and large differences in melting points and specific gravity. Therefore, we investigated the preparation of HEAs by mechanical alloying (MA), which produces an alloy powder with a uniform microstructure, followed by consolidation by spark plasma sintering (SPS). In this study, CoCrFeNiTi HEA sintered after MA-SPS was subjected to direct current plasma nitriding with screen (S-DCPN) to evaluate the characteristics of the nitrided layer as a function of nitriding temperature. Ball milling with heptane in an argon atmosphere using pure powders of Co, Cr, Fe, Ni, and Ti as raw materials was performed for 50 h. Subsequently, sintered compacts were prepared by SPS and treated with S-DCPN at 673, 773, and 873 K for 15 h in 75% N 2 –25% H 2 at a gas pressure of 200 Pa. A screen made of austenitic stainless steel SUS316L was installed as an auxiliary cathode to ensure uniform heating and nitrogen supply during the plasma nitridation process. Then, X-ray diffraction test, cross-sectional microstructure observation, surface microstructure observation, cross-sectional hardness test, roughness test, glow discharge optical emission spectrometry, corrosion test, and wear test were performed on the nitrided samples. The corrosion test results demonstrated that corrosion resistance increased with decreasing nitriding temperature. Furthermore, the results of the roughness and wear tests confirmed that abrasive wear occurred on the specimens nitrided at 873 K.
Proceedings Papers
IFHTSE2024, IFHTSE 2024: Proceedings of the 29th International Federation for Heat Treatment and Surface Engineering World Congress, 107-113, September 30–October 3, 2024,
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In recent years, physical vapor deposition and chemical vapor deposition (CVD) methods have made significant advancements due to the growing demand for surface modification technologies. This study focuses on depositing diamond-like carbon (DLC) as a thin, hard film using plasma-enhanced CVD. DLC possesses properties such as high hardness, low friction, wear resistance, and chemical stability. However, a drawback is low adhesion caused by residual stress and differences in hardness between the film and the substrate material. Therefore, efforts are underway to improve adhesion by introducing a DLC intermediate layer containing metallic elements to reduce residual stress or by applying treatments to harden the substrate material, such as nitriding or carburizing. Active screen plasma nitriding (ASPN) is a nitriding method that eliminates edge effects and electrically insulates the sample during the process. However, during nitriding, deposits can cover the sample and slow down the nitriding rate. To address this, a nitriding method called "direct-current plasma nitriding with screen (S-DCPN)" has been developed. It involves applying a voltage to the sample and screen during ASPN to remove deposits via sputtering action, thereby increasing the nitriding rate. Although the duplex process of ASPN and DLC-coating deposition has been studied, there are limited reports on the duplex process with S-DCPN. This study investigates the effect of intermediate layer composition on mechanical properties by forming a nitrided layer on the surface of SUS304 through S-DCPN treatment, depositing a Si-DLC intermediate layer with varying compositions, and applying a DLC film on the top surface. The results demonstrate that the lower the Si ratio in the Si-DLC intermediate layer, the better the wear resistance. Furthermore, the study reveals that wear resistance and adhesion were improved compared to samples without S-DCPN treatment.
Proceedings Papers
IFHTSE2024, IFHTSE 2024: Proceedings of the 29th International Federation for Heat Treatment and Surface Engineering World Congress, 114-121, September 30–October 3, 2024,
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Surface modification involves the chemical or physical impartation of enhanced functionality to the surface of materials, and has become increasingly important in recent years. Nitriding is a surface modification method that hardens the surface of metallic materials by causing nitrogen to permeate and diffuse into the surface to form various nitrides or by supersaturating a solid solution of nitrogen in the metal. This is effective in improving the hardness, corrosion resistance, and wear resistance. Plasma nitriding, a type of nitriding process, has several advantages, such as low energy consumption, short processing time, and low environmental impact. In contrast, the conventional plasma nitriding method forms plasma on the surface of the treated material, which may cause phenomena that lead to defects in the treated material. Therefore, the directcurrent plasma nitriding with screen (S-DCPN) method reduces these problems because plasma is formed not only on the treated material but also on the surface of the screen. Stainless steel has excellent corrosion resistance; however, nitriding treatment above a certain temperature reduces the corrosion resistance owing to chromium nitride precipitation. In this study, the S-DCPN treatment, a type of plasma nitriding method, was applied to form a thick nitrided layer without reducing corrosion resistance. The S-DCPN treatment was performed using ferritic stainless steel SUS430 as the sample and austenitic stainless steel SUS304 as the screen material at treatment temperatures of 633 and 653 K, treatment times of 5 and 15 h, a gas pressure of 200 Pa, and a gas composition of 75% N 2 - 25% H 2 . Consequently, the α N phase with supersaturated nitrogen solid solution was identified under all conditions. Nitrogen diffusion and hardness increased with increasing treatment temperature and time. In the corrosion tests, corrosion resistance improved under all conditions.
Proceedings Papers
IFHTSE2024, IFHTSE 2024: Proceedings of the 29th International Federation for Heat Treatment and Surface Engineering World Congress, 193-200, September 30–October 3, 2024,
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Carbide free bainitic microstructures can be developed via different thermal processing routes, and the details affect the scale and morphology of the microstructural constituents. In this study, bainitic microstructures are formed by either a controlled cooling process or an austempering process to evaluate the relationship between microstructure and mechanical properties in a 0.2C - 2Mn - 1.5Si - 0.8Cr steel containing small amounts of Nb, Ti, B, and N, and the results are compared to a 4140 steel processed via quenching and tempering. The resulting microstructures are characterized with scanning electron microscopy. When compared to microstructures produced via austempering, microstructures produced with a controlled cool exhibit an increased variety of transformation products, specifically regarding size and distribution of martensite-austenite constituents within a lath-like bainitic ferrite matrix. Nanoindentation testing shows that different transformation products exhibit significantly different local hardness. In all (primarily) bainitic conditions tested for these materials, the martensite/austenite constituent exhibits the highest hardness, followed by the lath bainitic ferrite/retained austenite constituent. Granular bainite and coarse bainitic constituents exhibit the lowest relative hardness in the conditions where they are observed.
Proceedings Papers
IFHTSE2024, IFHTSE 2024: Proceedings of the 29th International Federation for Heat Treatment and Surface Engineering World Congress, 332-337, September 30–October 3, 2024,
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The increasing demand for accurate fatigue modeling of powder metallurgy components in automotive, aerospace, and medical industries necessitates improved knowledge of composition-microstructure interactions. Variations in feedstock composition and thermomechanical history can produce unique microstructures whose impact on fatigue performance has not been adequately quantified. When characterizing additively manufactured 316L that is within nominal standard chemistry limits, oxide and nitride species were observed preferentially in the specimen contour region. Thermodynamic simulations provide evidence of segregation of the low manganese and high nitrogen composition driving this precipitation of these phases. When present in the specimen, they promoted brittle fracture mechanisms during fatigue.
Proceedings Papers
María Isabel Bucio-Herrejón, Monserrat Sofía López-Cornejo, Héctor Javier Vergara-Hernández, Octavio Vázquez-Gómez
IFHTSE2024, IFHTSE 2024: Proceedings of the 29th International Federation for Heat Treatment and Surface Engineering World Congress, 352-357, September 30–October 3, 2024,
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Controlled cooling conveyor system is known, as the starting point for quality processing of wire rod products, obtaining good mechanical properties. This process guarantees excellent performance with high production rates. In order to process several steel grades and different diameters, it is necessary to determine, the different austenitization temperatures and cooling rates that will control austenitic grain growth and, consequently, the pearlite interlamellar spacing. In this work, dilatometric analysis was performed to determine critical temperatures for an hypoeutectoid steel during heating and controlled continuous cooling, similar to the industry conditions for heat treatment. Metallographic analysis and microhardness test validated the results obtained during the dilatometry tests. The critical temperatures will be employed to understand the effect of the thermal conditions in controlled cooling process and adjust the conditions for better results in the austenitic grain size.