High Speed Steel Research Articles

Punching of Ultra-High-Strength Spring Strips: Evolution of Cutting Edge Radius up to 1,000,000 Strokes for Three Punch Materials

Punching of ultra-high-strength spring steel causes critical stresses in the tools. Pronounced wear and even spontaneous failure may occur. Wear of the punches influences the quality of the cutting surfaces of the blanked parts, which is predominantly determined by the cutting edge radius. The radius differs with an increasing number of strokes depending on the punch material. However, there are no studies characterizing the influence of the cutting edge radius on the cutting surface quality on an industrial scale, i.e., considering a very high number of strokes. In the presented study, punches made of high-speed steel, powder metallurgical steel and carbide were used to punch the ultra-high-strength steel 1.4310 (Rm = 1824 MPa) up to 1,000,000 strokes. The experiments were stopped at defined number of strokes, the punches were removed, nondestructively characterized regarding cutting edge radius and wear and reinstalled. It turned out that the radius differed significantly over the number of strokes and, further, varied depending on the punch material. Remarkably, the most low-cost material, precisely the high-speed steel, showed the smallest cutting edge radius of 16 µm and brought the parts with the best cutting surface quality (more than 30% burnish zone) after the maximum number of strokes. The results indicate clearly that the cutting edge radius develops differently for each regarded material and at different number of strokes. Therefore, it is of utmost importance to perform wear tests on different numbers of strokes under industrial conditions. With the knowledge gained, it will be possible to design optimized punches with lower costs and increased lifetime.

Adapting the Surface Integrity of High-Speed Steel Tools for Sheet-Bulk Metal Forming

New manufacturing technologies, such as Sheet-Bulk Metal Forming, are facing the challenges of highly stressed tool surfaces which are limiting their service life. For this reason, the load-adapted design of surfaces and the subsurface region as well as the application of wear-resistant coatings for forming dies and molds made of high-speed steel has been subject to many research activities. Existing approaches in the form of grinding and conventional milling processes do not achieve the surface quality desired for the forming operations and therefore often require manual polishing strategies afterward. This might lead to an unfavorable constitution for subsequent PVD coating processes causing delamination effects or poor adhesion of the wear-resistant coatings. To overcome these restrictions, meso- and micromilling are presented as promising approaches to polishing strategies with varying grain sizes. The processed topographies are correlated with the tribological properties determined in an adapted ring compression test using the deep drawing steel DC04. Additionally, the influence of the roughness profile as well as the induced residual stresses in the subsurface region are examined with respect to their influence on the adhesion of a wear-resistant CrAlN PVD coating. The results prove the benefits of micromilling in terms of a reduced friction factor in the load spectrum of Sheet-Bulk Metal Forming as well as an improved coating adhesion in comparison to metallographic finishing strategies, which can be correlated to the processed roughness profile and induced compressive residual stresses in the subsurface region.

Cutting forces during drilling of a SiCp reinforced Al-7075 matrix composite

Abstract In this study, an Al-7075 matrix alloy reinforced and by 5, 10, and 15 wt% silicon carbides were produced as a composite material using the stir casting method. An investigation of the hardness, density, and microstructure of the matrix alloy and the composite materials was conducted. The following instruments were used for the microstructure studies: optical microscope and scanning electron microscope (SEM). The machinability behavior of the produced composite materials was investigated by using the drilling method with a three-axis computer numerical controlled (CNC) milling center. High-speed steel (HSS) and titanium nitride (TN)-coated HSS drill bits were used in the machinability tests. As drilling process cutting conditions three different feed rates (FRs) of 0.05, 0.10, and 0.15 mm·rev−1 and three different cutting velocities (CVs) 15, 20, and 25 m·min−1 were applied. The effects of cutting conditions such as FR, CV, reinforcement phase ratio, and cutting tool type on cutting forces such as thrust force (TF) and torque (TQ) in the drilling process were studied in detail. According to the experimental results, TF and TQ decreased with the increase in the CV and increased with the increase in the FR.

Microstructure, residual stress, and mechanical property evolution of a spray-formed vanadium-modified high-speed steel processed by post-heat treatment

A vanadium-modified high-speed steel (HSS) manufactured by spray forming (SF) process was subjected to different heat treatment processes and the resultant microstructural evolution and mechanical properties were investigated. In-situ high-temperature Vickers indentation associated with high-temperature tensile tests were utilized to evaluate the changes in hardness and residual stress with temperature for samples processed by annealing. Moreover, the effect of quenching temperature on hardness, bending strength and impact toughness was investigated. The secondary carbide precipitation behavior and its strengthening mechanisms were discussed in combination with transmission electron microscopy (TEM) characterization. A possible mechanism was proposed to elucidate the evolution of carbide precipitation behavior during different heat treatment processes. We envision the results gained from the present study would provide useful guidance for understanding the evolution of microstructure and mechanical properties of spray-formed HSSs processed by different heat treatment conditions and optimizing the alloy design and post–thermal mechanical processing of HSS.

Investigations of fatigue crack propagation in ER8 railway wheel steel with varying microstructures

In this study, fatigue crack occurrences and propagations of high-speed railway wheel steel grade ER8 were investigated through both experiments and FE simulations. Three varying microstructures of the wheel steel including as-received, ferrite- and bainite-containing microstructures, which were obtained by specific heat treatment routes, were characterized. Stress-controlled fatigue tests were carried out for determining relationships between crack propagation rate and stress intensity factor of the steels. In addition, FE simulations of fatigue crack developments on both macro- and micro-scale using representative volume element (RVE) 2D models were conducted with consideration of microstructural features. The extended finite element method (XFEM) coupled with the Paris law was applied in the cyclic simulations for predicting crack propagation. For the microstructure level, flow stress-strain curves based on micromechanics approach and corresponding fatigue damage parameters of different phases in steels were identified and afterwards calibrated with experimental results. Finally, influences of ferrite, pearlite and bainite on fatigue crack resistance in the wheel steel were precisely examined by the RVE model. It was found that fatigue micro-cracks mostly initiated close to interface regions between soft and hard phases. The bainitic phase could obviously retard fatigue crack propagation of steel, whereas the ferritic phase contrarily exhibited deteriorated crack resistance. Moreover, the proposed framework could be acceptably employed for predicting fatigue crack propagation behavior and its rate in railway wheel subjected to microstructure changes occurred.

Effect of Cooling Rate on Carbide Characteristics of the High Vanadium High-speed Steel

Effect of Cooling Rate on Carbide Characteristics of the High Vanadium High-speed Steel

Computational Alloy Design for Process-Related Uncertainties in Powder Metallurgy

An integrated computational materials engineering approach to the design of alloys for supersolidus liquid phase sintering has been developed. The method aims to minimize the sensitivity of the alloys to variabilities in material (e.g., composition) and process parameters (e.g., temperature) during sintering while also maximizing mechanical properties. This is achieved by developing a fast acting and high throughput design models that can quantify the processability and the resulting mechanical properties. A highly processable alloy is defined as one that is tolerant to both composition and process conditions such that changes in either do not materially affect the alloy properties. The design models are validated using experimental data from the literature and the computational design approach is demonstrated by designing unique high-speed steels with enhanced processability for powder metallurgy.

A modern-day alchemy: Double glow plasma surface metallurgy technology

In the long history of science and technology development, one goal is to diffuse solid alloy elements into the surface of steel materials to form surface alloys with excellent physical and chemical properties. On the basis of plasma nitriding technology, double glow plasma surface metallurgy technology has answered this challenge. This technology, which seems to be a modern-day alchemy, can use any element in the Periodic Table of chemical elements, including solid metal elements and their combinations, to form many types of surface alloyed layers with high hardness, wear resistance, corrosion resistance, and high temperature oxidation resistance on various metal materials. For example, nickel base alloys, stainless steels, and high speed steels are formed on the surfaces of ordinary carbon steels; high hardness, wear resistance, and high temperature oxidation resistance alloys are formed on the surface of the titanium alloy. This article briefly introduces the formation and principle of double glow plasma surface metallurgy technology and summarizes the experimental results and industrial applications. The significance and development prospect of this technology are discussed.

The influence of tool quality on the machining of additive manufactured and powder metallurgy titanium alloys.

This study was carried out to investigate the impact the quality of the drill bits has on the machining behavior of additive manufacturing (AM) and powder metallurgy (PM) titanium alloys. Therefore, commercially available drill bits which typically reflect two extremes of drill bit quality were selected. The performance of coated carbide twist drills, typically recommended for the drilling of wrought titanium alloys was compared with that of high-speed steel (HSS) drills. The average torque value, specific cutting energy (SCE), and tool wear were used to evaluate the drilling performance of AM and PM titanium alloys. The results of drilling tests revealed the application of the coated carbide drill resulted in lower torque and SCE values, less flank wear, and lower build-up-edge (BUE) compared with the uncoated HSS drill bits for AM fabricated titanium alloys. However, the carbide drill appeared to offer negligible improvement over the uncoated HSS drill when employed with the PM fabricated titanium alloy. In spite of the improvement in the drilling performance offered by the carbide drills for the AM titanium alloy, TiB intermetallic particles (part of the AM titanium microstructure) contributed to the damage of the coated carbide drill which would limit the drill lifetime.

Duplex surface modification of tool steel - deposition of a WN film and subsequent electron-beam modification

In this study, we demonstrate a combined treatment technique of R18 high-speed tool steel comprising deposition of a WN coating followed by electron-beam surface treatment (EBT). In order to understand the influence of the deposited WN coating on the resultant structure and properties, an uncoated specimen was directly electron-beam treated under the same EBT technological conditions. The structure of the specimens was studied by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The microhardness was also investigated. The phase composition consisted of a double phase structure of Fe and M6C carbides in both cases. The microstructure was significantly finer in the case of an EBT of the steel with WN coating, leading to a much higher microhardness in comparison with the case without WN.

RESEARCH OF THE PROCESS OF HIGH VOLTAGE ELECTRIC DISCHARGE SINTERING OF P6M5 RAPID STEEL POWDER

Studies have been carried out to study the process of high-voltage electric-discharge sintering of powder of high-speed steel R6M5. The process of high-voltage electric-discharge sintering of powders is accompanied by a complex of electrophysical, thermodynamic and mechanical phenomena that affect the sintering processes of samples and their properties.  It was found that the process of high-voltage electric-discharge sintering of powders of P6M5 steel is accompanied by compaction of the powder as a result of sintering of particles, as well as by the action of compressive stresses on the sample from the powder. The shape and size of particles, the nature of surface films, the size and shape of the matrix have a great influence on the process of high-voltage electric-discharge sintering. Factors affecting the strength properties of samples include the particle size distribution of the powder, its initial electrical resistance, and technological processing parameters, such as discharge energy and discharge current density.

Performance of High-Speed Steel Drills in Wet Drilling Inconel 718 Superalloy

Performance of High-Speed Steel Drills in Wet Drilling Inconel 718 Superalloy

Microstructural variations and mechanical properties of deep cryogenic treated AISI M35 high-speed steel tempered at various temperatures

Deep cryogenic treatment applied in high-speed steel yielded promising results, and it was found that tempering played a vital role. This paper systematically studied the effect of tempering temperatures on the microstructural composition (residual austenite, martensite, and carbides) and mechanical properties (Vickers hardness and impact toughness) of AISI M35 high-speed steel subjected to deep cryogenic treatment. An increase in the tempering temperatures facilitated the transformation of residual austenite and the formation of martensite blocks corresponding to a decrease in the number of dislocations. Moreover, the carbide precipitation (secondary carbides and nanoscale carbides) began at a tempering temperature of 350 °C, increased at 450 °C, and reached its maximum at 550 °C. The fracture mechanism on the micro-level could be interpreted as follows: cracks occurred in the carbides with larger sizes (primary carbides and large secondary carbides) and at the carbide/matrix interface, and small secondary carbides decohered at the interface, forming microvoids and facilitating plastic deformation. In addition, the specimen tempered at 150 °C exhibited the highest hardness of 880.4 HV1 due to the highest number of dislocations. The impact toughness of the sample tempered at 550 °C was the best, namely 2.50 MJ m−2, due to an increase in the number of martensite block boundaries and the more homogeneous carbide precipitation.

A Review: Double Multivariate Nonlinear Regression Constitutive Model of High-Speed Train Axle Steel 40CrNiMo during Hot Tension

A Review: Double Multivariate Nonlinear Regression Constitutive Model of High-Speed Train Axle Steel 40CrNiMo during Hot Tension

Micromechanisms and modelling of crack initiation and growth in tool steels: role of primary carbides

AbstractMicromechanisms of damage initiation and crack growth in high speed and cold work steels are investigated using scanning electron microscopyin situexperiments. The role of primary carbides in initiation and growth of cracks in tool steels is clarified. It is shown that initial microcracks in the steels are formed in primary carbides and then join together. A hierarchical finite element model of damage initiation, which included a macroscopic model of the deformation of the specimen under real experimental conditions and a mesomechanical model of damage in real microstructures of steels, was developed. Using the hierarchical model, the conditions of local failure in the steels have been obtained. In order to study the effect of carbide arrangement on fracture, numerical simulations of fracture in steels with different ideal carbide arrangements were carried out and compared with each other. It is found that the heterogeneous arrangements of primary carbides can lead to strong deviations of a crack from the mode I path and, therefore, to a significant increase of the fracture energy of the steels.

Effect of Fe content on type and distribution of carbides in medium-entropy high-speed steels

Effect of Fe content on type and distribution of carbides in medium-entropy high-speed steels

The Impact of Cutting Modes on the Output Turn-Milling Parameters for High-Speed Steel

The article describes the orthogonal turn-milling technology applied for powder high speed steels. The cutter with carbide inserts was used in the experiments. The orthogonal turn-milling model was developed to improve the surface quality by choosing optimal cutting modes based on the simulation results. The mathematical model makes it possible to predict geometric surface deviations. The impact of cutting speed, tool feed and radial depth of cut on the geometric surface parameters was identified. The results make it possible to achieve the satisfactory level of surface quality without deteriorating the machining productivity. The avenues for further research are outlined.

Machinability investigations through novel controlled flushing characteristics in wire electric discharge machining of M42 high-speed steel

Machinability investigations through novel controlled flushing characteristics in wire electric discharge machining of M42 high-speed steel

Discharge characterization and technological application of an arc ion plating with a hollow cathode vacuum arc

In an effort to reduce macroparticle defects in arc ion plating, a hollow cathode vacuum arc was added to an arc ion plating deposition chamber, so that the discharge from the hollow cathode vacuum arc was between the target and the substrate. AlTiN coatings were deposited using this technique (hollow cathode vacuum arc enhanced arc ion plating or HCVA-AIP) on high-speed steel substrates, and analyzed using scanning electron microscopy and X-ray diffraction. The hollow cathode vacuum arc was found to reduce the number and size of macroparticles in the deposited coatings and to increase the deposition rate. The hollow cathode vacuum arc also reduces the arc ion plating target voltage, by up to 29% (to 12 V) under the conditions studied here. Using this technique, the rate of Al ionization in the target is enhanced, resulting in the formation of AlN in the coating. This effect is strengthened at a higher hollow cathode vacuum arc discharge current.

Experimental Investigation on Tribological Behaviour of AA6066: HSS-Cu Hybrid Composite in Dry Sliding Condition

Aluminum is among the most preferred materials based on the desired properties. This investigation focused on to evaluate the wear rate of the AA6066 aluminium alloy composite by using pin-on-disc apparatus. The composites were created with three materials such as AA6066 alloy, high-speed steel, and copper which have a volume percentage variation of 92%, 5%, and 3%, respectively. These three parameters were considered for the experimental results of the wear rate such as load applied, sliding speed, and sliding distance. Experimental results of the composites were compared using an applied load of 20 N, a sliding velocity of 3.0 m/s and 1800 m of sliding distance with AAHSSCu reinforced composites offering a minimum wear rate. Similarly, using a 40 N applied load, the minimum wear rate is obtained. Further increasing the applied load to 60 N with 600 m of sliding distance provided a lower wear rate. The various graphical representations such as three-dimensional surface plots, contour plots, and bar charts were used for the experimental results. Wear rate consequences were expressed individually compared based on the considered parameters. Experimental results were having the reliability of nearly ninety-one percentage with only wear rate being focused. Finally, an optimized wear rate is obtained at the sliding distance of 1200 m with an applied load of 40 N and a spindle speed of 3 m/s.