Red Hardness Research Articles

High-temperature tribological properties of (TiZrNbMoTa)N and (TiZrNbMoTa)CN ceramic coatings

As dry-cutting tool coatings, high-entropy ceramics (HECs) exhibit excellent hardness, toughness, and wear resistance properties. However, the hardening mechanism of HEC coatings and their mechanical and frictional properties under high-temperature conditions have not been studied. In this study, we successfully prepared (TiZrNbMoTa)N high-entropy nitride (HEN) and (TiZrNbMoTa)CN high-entropy carbon nitride (HECN) coatings using reactive magnetron sputtering technology. The strengthening mechanism and thermodynamic properties of HEN and HECN coatings were systematically studied using the Debye-Grüneisen quasi-harmonic approximation model combined with density functional theory (DFT) calculations. At room temperature (RT, 25 °C) and high temperature (HT, 500 °C), the microhardness of HECN is 62 % and 56 % higher than that of HEN, respectively. Especially at RT, the microhardness of HECN reaches 46.37 GPa. Through in-situ XRD, in-situ nanoindentation, and high-temperature friction and wear analysis, we conducted in-depth research on the phase stability, high-temperature mechanical properties, and high-temperature tribological properties of HECs coatings in high-temperature. XRD test results show that HEN and HECN coatings exhibit a single-phase FCC structure and maintain good stability under HT. DFT calculation results show that the M − C bond in HECN is stronger than the M − N bond in HEN, which is why the HECN coating is harder. At HT, the wear rate of HECN coating is only reduced by 10 % compared with HEN coating. Different from RT, under high-temperature conditions, the primary wear mechanism of the coating is oxidative wear. The coating's red hardness and friction coefficient (COF) have a limited impact on the coating's high-temperature anti-wear performance. This research provides a theory and technical basis for designing and preparing protective coatings with high hardness and low friction coefficient.

Microstructure evolution and properties of LaB6 modified carbon-free sintered FeCoMo steels

LaB6-modified carbon-free FeCoMo steels with nano-precipitated phase strengthening have shown excellent sintering and mechanical properties, which enhances their application potential. The results showed that LaB6 promoted the precipitation of sub-nanometer μ-phase particles from the matrix and reduced the formation of impurity phases during the sintering process. The addition of 0.2 wt% LaB6 increased the hardness, wear resistance and red hardness of FeCoMo steel by 5.1 %, 26.3 % and 12.6 %, respectively. This study creates conditions for the application of carbon-free FeCoMo steels by introducing LaB6 to improve their sintering properties and precipitated phase strengthening efficiency.

Design and Optimization of Heat Treatment Process Parameters for High-Molybdenum-Vanadium High-Speed Steel for Rolls.

High-molybdenum-vanadium high-speed steel is a new type of high-hardenability tool steel with excellent wear resistance, castability, and high-temperature red hardness. This paper proposes a composition design of high-molybdenum-vanadium high-speed steel for rolls, and its specific chemical composition is as follows (wt.%): C2%, Mo7.0%, V7.0%, Si0.3%, Mn0.3%, Ni0.4%, Cr3.0%, and the rest of the iron. This design is characterized by the increase in molybdenum and vanadium in high-speed steel to replace traditional high-speed steel rolls with the tungsten element in order to reduce the heavy elements' tungsten-specific gravity segregation caused by centrifugal casting so that the roll performance is uniform and the stability of use is improved. JMatPro (version 7.0) simulation software is used for the composition design of high-molybdenum-vanadium high-speed steel. The phase composition diagram is analyzed under different temperatures. The content of different phases of the organization in different temperatures is also studied. The martensitic transformation temperature and different tempering temperatures with the different types of compounds and grain sizes are calculated. The process parameters of heat treatment of high-molybdenum-vanadium high-speed steel are optimized. The selection of carbon content and the temperature of M50 are calculated and optimized, and the results show that the range of pouring temperatures, quenching temperatures, annealing temperatures, and tempering temperatures are 1360~1410 °C, 1190~1200 °C, 818~838 °C, and 550~600 °C, respectively. Scanning electron microscope (SEM) analysis of the samples obtained by using the above heat treatment parameters is consistent with the simulation results, which indicates that the simulation has important reference significance for guiding the actual production.

Hot Work Mold Repaired via Hot Isostatic Pressing towards High Red Hardness

Repairing hot work molds can extend their lifespans and reduce the production costs. This study presents a proposed method for enhancing the red hardness and strength of repaired molds. The method involves utilizing PM23 high-speed steel powder to repair H13 steel molds with two distinct surface states through the process of hot isostatic pressing (HIP). The internal microstructure changes, bonding state, fracture morphology, and crack extension behaviors of the repaired molds are characterized using scanning electron microscopy and electron backscatter diffraction technology. Additionally, the mechanical properties, including red hardness and tensile strength, are quantitatively analyzed. The findings indicate that the repaired area in the sandblasted sample exhibits a rough and uneven structure, demonstrating exceptional toughness. The tensile strength of the repaired region is approximately 1195.42 MPa, while the hardness measures around 672.8 HV. These properties effectively enhance the performance of the molds. The experimental findings indicate that HIP can effectively restore molds, resulting in enhanced red hardness and improved toughness, particularly when combined with sandblasting as a pretreatment method.

Increasing the red hardness of the deposited layer of high-speed steel by thermomechanical effects

Increasing the red hardness of the deposited layer of high-speed steel by thermomechanical effects

Effects of sintering temperatures on the microstructure and mechanical properties of S390 powder metallurgy high-speed steel

High-performance complex gear cutters and high-temperature bearings are just some of the applications where high-speed steels (HSSs) shine as a preferred material choice owing to their high hardness and outstanding wear resistance. In this work, the effects of sintering temperature on the microstructure and mechanical properties of S390 HSS prepared via spark plasma sintering (SPS) were investigated with a range of sintering temperatures from 930°C to 1,090°C, a uniaxial pressure of 50 MPa, and a holding time of 5 min. The results demonstrated that the improvements in density, hardness, red hardness, and three-point bending strength were confirmed as the sintering temperature increased from 930°C to 1,090°C. Temperature-induced microstructure evolutions were assessed for their contribution to property enhancement, such as powders with varying dimensions and carbides with diverse morphology and diameter. The specimen with the best comprehensive mechanical properties (67.1 HRC and 1,196.67 MPa) was prepared at 1,050°C via SPS. The wear coefficients decreased as the sintering temperature increased, and the observation results of worn surfaces of test pins confirmed that abrasive wear and oxidation wear dominated the wear experiments. Furthermore, the wear mechanism of dense and porous SPS HSS was illustrated and analyzed in terms of the debris and trapped carbides.

Effect of niobium and austenitizing temperature on the microstructures and properties of spray-deposited AISI M3:2 high speed steel

The microstructure and properties of niobium-containing AISI M3:2 high speed steels (HSSs) fabricated by spray forming and traditional casting have been investigated. The results show that fine and uniformly-distributed grains without macrosegregation appeared in the as-deposited HSSs that differ from those of as-cast HSSs. Nb mostly appears in primary MC carbides, whereas it contributes less to the formation of M6C carbides. The high stabilization of Nb-rich MC carbides can pin the grain boundaries during high-temperature austenitizing process, thus conferring a fine grains and raising the content of dissolved alloying elements. Enhanced precipitation strengthening and fine dispersion of NbC carbides throughout the matrix contribute to the high hardness and red hardness of Nb-containing HSS.

Effect of deep cryogenic treatment on microstructure and properties of M35 high speed steel

The effects of cryogenic treatment on microstructure, hardness, red hardness and wear resistance of M35 high speed steel(HSS) were studied by means of scanning electron microscope, X-ray diffractograph, friction and wear tester and Rockwell hardness tester. The results show that with the increase of tempering temperature, the residual austenite in M35 HSS decreases and the grain size increases gradually. After deep cryogenic treatment (DCT), the grain size of M35 HSS is refined and the wear volume is reduced. DCT at 525°C has the best wear resistance. With the increase of tempering temperature, the hardness of M35 HSS decreases first and then increases, and finally decreases sharply. The Rockwell hardness of M35 HSS at 525 °C is the highest, which is 67.1 HRC. The peak hardness of Rockwell increased by 0.7 HRC and the tempering temperature decreased from 550 °C to 525 °C, which showed good stability of red hardness.

CRUCIBLE CPM REX 54 HS

Abstract Crucible CPM Rex 54 HS is a cobalt-bearing high speed tool steel that is produced by the proprietary Crucible Particle Metallurgy (CPM) process. It combines the wear properties of the popular high vanadium M4 grade with the red hardness of the cobalt-bearing M35/Crucible CPM Rex 45 HS grades. Crucible CPM Rex 54 HS may be used as an upgrade for improved red hardness over M3 or M4 without giving up the abrasion resistance, or as an upgrade for improved wear resistance over M35 or Crucible CPM Rex 45 HS without giving up the red hardness. This datasheet provides information on composition, physical properties, microstructure, hardness, and elasticity. It also includes information on wear resistance as well as heat treating and surface treatment. Filing Code: TS-818. Producer or source: Crucible Industries LLC.

Technological aspects of borate glass–ceramics preparation doped with transition metals for optoelectronic applications

Chromium-doped borate glass-ceramics are prepared at different temperatures via bulk crystallization of the borate glass matrix. The temperature influence on the spectral and operational characteristics of the material is observed. Rod-shaped LiAl7B4O17 crystals nucleate in a glassy matrix during two stage heat treatment. Borate glass-ceramics possess luminescence in the 650–800 nm region when excited with “green” light. An increase in the annealing temperature of glass-ceramics lead to several changes: (1) the luminescence quantum yield increase from 13% to 50%, (2) color coordinates of glass-ceramics luminescence shift towards to the red spectral region, (3) hardness and resistance to acid solutions of glass-ceramics increase. XRD experiments are carried out within the direct heating of a glass sample. The results show that the maximum size of nanocrystals was reached at a temperature of 600 °C, which coincided with the maximum of the exothermic region on the DSC curve. Thus, the spectral and operational properties of borate glass-ceramics exceed those of the initial borate glass, which makes borate glass-ceramics doped with chromium ions promising material for creating red and near infra-red emitters .

Improved Red Hardness and Toughness of Hot Work Die Steel through Tungsten Alloying

In order to elucidate the relationship between red hardness/toughness and tungsten content, strong carbide-forming element tungsten was added to a 5 wt.% Cr medium carbon steel (Cr5) in melting. After normalization and forging, the vacuum gas-quenched experimental steels were tempered at 560 and 600 °C for 10-40 h, respectively. Rockwell hardness and un-notched impact energy were evaluated. It was revealed that the precipitation phases play a critical role in the mechanical properties of the steels. The tungsten element effectively improved the red hardness of the steel by 6.3-15.8% when tempering at 600 °C for 10-40 h, while the corresponding impact toughness holds at the same level, about 250J, as Cr5 steel. Through observations by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), mesoscales carbides were found with a structure of (Fe, Cr, W, Mo, V)6C. It was deduced that tungsten element acts a positive role in inhibiting the coarseness of secondary M6C-type carbides and impeding the formation of M23C6 and M7C3, and thus enhances the thermal stability of Cr5W steel at elevated temperature. Furthermore, the tempering stability prediction model was constructed to predict the red hardness of tungsten-containing Cr5W steel.

Improved mechanical properties by nanosize tungsten-molybdenum carbides in tungsten containing hot work die steels

AISI H13 die steel with substitution of tungsten for vanadium (H13–W) was produced through vacuum induction melting and forging, followed by 1050°C-quenching and 600°C-tempering. Through 10–40 h of 600°C-tempering, H13–W exhibits superior red hardness as compared to H13 steel. The increments of hardness (4-6HRC) as well as yield strength were deducted to the precipitated M6C-type carbides with sizes ranging from 10 nm to 400 nm. Two classifications of carbides are identified. Type I of carbides has the nano size of 8–50 nm, and type II of undissolved primary carbides ((Fe1.34Mo1.62 Cr2.95W0.09)C) has the bigger size of 100–400 nm. The yield strength increments (Δσy) were modeled by a bivariate distribution of nano and undissolved precipitates. The calculated major strengthening effects from type I nano carbides in H13–W/H13 steels were close to the deduced values by Hall-Petch theory, they were 1053 MPa and 965.8 MPa, respectively. According to the calculation on equilibrium solubility of precipitations of MoC/Mo2C and WC/W2C, it was testified that MoC, Mo2C, WC and W2C were wholly dissolved into austenite at 1050 °C of quenching, followed by precipitating in large quantities in the form of nanosize carbides at 600oC-tempering.

深冷处理时间对 M2 高速钢红硬性的影响

深冷处理时间对 M2 高速钢红硬性的影响

Технологическое исследование влияния параметров механической обработки на срок службы инструмента

Introduction. The machinability is typical criteria to be investigated and different authors suggested different parameters describing its quantification. Different parameters i. e. speed, feed, depth of cut, tool work-piece combination, machine types and its condition, cutting fluid, machinist expertise, etc. are contributing directly to the tool life. The selection of the tool for the machining impacts greatly on the economic viability of the machining in terms of energy usage and tooling costs. The method of investigation. The current research emphasis mainly on tool life investigation when machining the mild steel specimens ISRO 50, BIS 1732:1989 at constant cutting speed i.e. 200 m / min. In the industries the mild steel material is commonly used for various products manufacturing. Considering the high demands on productivity and surface finish, machining at 200 m / min is the preferred. The computerized numerical control machine (CNC DX-150) is used for the turning. The four corner insert (TNMG 120408) is used for different machining times i.e. 10, 15, 20 and 25 minutes respectively. The flank wear of the tool is measured with calibrated optical microscope. The temperature of the tool corner during machining is continuously measured for possible impact of temperature on bonding properties of the tool insert and impact on red hardness. Results and discussion. The plot of flank wear vs. machining time will give the value of tool life. The other quality output parameter, such as surface roughness, is measured after machining, indicating surface irregularities in root means square value. Efforts have been made to identify the relationship of tool life, machining time, the quantity of metal removed, surface roughness, and tool bit temperature.

Effective Fundus Image Decomposition for the Detection of Red Lesions and Hard Exudates to Aid in the Diagnosis of Diabetic Retinopathy.

Diabetic retinopathy (DR) is characterized by the presence of red lesions (RLs), such as microaneurysms and hemorrhages, and bright lesions, such as exudates (EXs). Early DR diagnosis is paramount to prevent serious sight damage. Computer-assisted diagnostic systems are based on the detection of those lesions through the analysis of fundus images. In this paper, a novel method is proposed for the automatic detection of RLs and EXs. As the main contribution, the fundus image was decomposed into various layers, including the lesion candidates, the reflective features of the retina, and the choroidal vasculature visible in tigroid retinas. We used a proprietary database containing 564 images, randomly divided into a training set and a test set, and the public database DiaretDB1 to verify the robustness of the algorithm. Lesion detection results were computed per pixel and per image. Using the proprietary database, 88.34% per-image accuracy (ACCi), 91.07% per-pixel positive predictive value (PPVp), and 85.25% per-pixel sensitivity (SEp) were reached for the detection of RLs. Using the public database, 90.16% ACCi, 96.26% PPV_p, and 84.79% SEp were obtained. As for the detection of EXs, 95.41% ACCi, 96.01% PPV_p, and 89.42% SE_p were reached with the proprietary database. Using the public database, 91.80% ACCi, 98.59% PPVp, and 91.65% SEp were obtained. The proposed method could be useful to aid in the diagnosis of DR, reducing the workload of specialists and improving the attention to diabetic patients.

Experiments, analysis and parametric optimization of roll grinding for high-speed steel W6Mo5Cr4V2

Due to the rapid development of the modern industry, people have higher and higher requirements on the rolling speed and quality of steel. The performance of conventional cast-iron roll cannot supply production demands because it contains higher chrome-nickel elements. The high-speed steel W6Mo5Cr4V2 with high service life, red hardness and wear resistance becomes a promising material of roll. However, the above characteristics bring great difficulties to roller repairing. Within this study, the high-speed steel W6Mo5Cr4V2 was processed with roll grinding at various grinding conditions (grain size, workpiece speed and depth of grinding) by using Taguchi design method, and the grinding process parameters are analysed and optimized according to the values of surface roughness and the depths of microhardness alterations. To obtain the optimized parameters, the values of surface roughness and microhardness alterations were analysed with grading methods of synthesizing multiple guidelines. Also, a confirmatory test was done to confirm the optimized parameters obtained from the above methods. The results of this work may provide the knowledge/database of the roll grinding process of high-speed steel W6Mo5Cr4V2 at given grinding parameters.

Morphology, Hardness and Wear Properties of Plasma Cladding NiCrCu Coating on M2 High-Speed Steel

To improve the cutting performance, the red hardness and wear resistance of M2 high-speed steel, as well as expand the application field, in this work, a coating was fabricated via plasma cladding on M2 high-speed steel using Ni, Cr and Cu alloy elements as precursor materials. The distribution and composition of alloying elements, microhardness and wear resistance of the coating were studied. The results show that the NiCrCu cladding layer contains many types of carbides. The secondary hardening caused by the dispersion of carbides can significantly improve the hardness, red hardness and wear resistance of material. The hardness of cladding layer is above 950 HV, after holding at 600 °C for 4 h, the hardness is above 932 HV. The alloy elements are evenly distributed, but, due to the rapid solidification after the cladding, there are composition fluctuations in the longitudinal direction. The wear resistance of the cladding layer is excellent; the wear rate is reduced from 1.75 to 1.44 × 10−6 mm3 N−1 m−1 or less; and the wear mechanism is a combination of abrasive wear and adhesive wear.

Effect of Starting Microstructure in High Speed Steel on the Grain Refinement Potency of Electropulsing Treatment

High speed steels (HSSs) are widely used materials for tools production, which grab a third part of the global cutting tool market. Heat treatment is an indespensable process for the fabrication of HSS tools. Modifications of carbides and grain size of the matrix are two main aspects for the heat treatment of HSSs. In order to obtain better wear property, hardness or red hardness, modification of carbides attracts more researchers’ attention, but grain refinement benefits to the toughness and tool life. Compared with the grain refinement methods used for other steels, such as controlled rolling, available method for grain refinement of HSSs seems deficient. Our previous study provided a new method to produce ultrafine grained M2 steel, but the effect of the starting structures on the grain refinement potential of electropulsing treatment (EPT) was not involved. Results in this work show that the grain size can both be refined or even ultra-refined by EPT, whatever the difference in the starting structures. But the austenite transformation of the matrix was completed at lower peak temperature when using starting tempered structure. And the pre-tempered M2 samples have higher hardness than that obtained after heat treatment or EPT when using the starting annealed structures.

BÖHLER S700

Abstract Böhler (or Boehler) S700 tungsten-molybdenum high-speed tool steel has good wear resistance and red hardness. This datasheet provides information on composition and physical properties. It also includes information on forming, heat treating, and machining. Filing Code: TS-778. Producer or source: Voestalpine BÖHLER Edelstahl GmbH & Co KG.

Application of transient nonlinear thermal analysis on quenching of hot die steel

Hot die steels contact with high temperature metals, and possess well thermal conductivity, wear resistance and red hardness. The carbon content should be controlled in the range of 0.3wt.% to 0.6wt.%, and added alloy elements to improve hardenability. The complex composition of the alloy affects its thermal and physical properties. For billets with large volume, it is difficult to measure the temperature of all parts. Through numerical simulation, the temperature field distribution in quenching process of hollow steel pipe with a length of 7 m is obtained by adopting the transient nonlinear thermal analysis algorithm of general finite element software. The results show that the steel temperature decreases to the target temperature of 19°C, it takes about 10 to 12 minutes for the thin wall and 18 to 20 minutes for the thick wall. It is about 4 minutes to descend martensite transition temperature of 265°C at the thick end. Steel temperature decreases to medium temperature, with the wall thickness increases, time slightly longer. The characteristics and phase changing latent heat of hot die steel quenching process are taken into account, and the corresponding treatment is carried out when setting thermophysical parameters. The accurate simulation results are obtained and have certain significance for the research of related materials heat treatment.