Properties Of Tool Steel Research Articles

Effectiveness of deep cryogenic treatment in improving mechanical and wear properties of cold work tool steels

In recent years, deep cryogenic treatment (DCT) is getting increased attention in many tooling applications as a mean to improve tool performance. However, contradictory results are reported indicating improved as well as deteriorated wear resistance. The goal of this work was to investigate effect of DCT on wear properties of tool steel and how they change depending on the tool steel type, and hardness and fracture toughness obtained. Results show that steel composition considerably affects the way how cryogenic treatment changes steel properties. For low carbon tool steel toughness properties can be improved for up to 70% at only minor hardness drop, but are quite limited in the case of high-speed steel, while at high carbon content both hardness and toughness are deteriorated. In general, DCT was found to result in reduced abrasive wear resistance except for cases of combined hardness and fracture toughness improvement.

Tool Steel Heat Treatment Optimization Using Neural Network Modeling

Optimization of tool steel properties and corresponding heat treatment is mainly based on trial and error approach, which requires tremendous experimental work and resources. Therefore, there is a huge need for tools allowing prediction of mechanical properties of tool steels as a function of composition and heat treatment process variables. The aim of the present work was to explore the potential and possibilities of artificial neural network-based modeling to select and optimize vacuum heat treatment conditions depending on the hot work tool steel composition and required properties. In the current case training of the feedforward neural network with error backpropagation training scheme and four layers of neurons (8-20-20-2) scheme was based on the experimentally obtained tempering diagrams for ten different hot work tool steel compositions and at least two austenitizing temperatures. Results show that this type of modeling can be successfully used for detailed and multifunctional analysis of different influential parameters as well as to optimize heat treatment process of hot work tool steels depending on the composition. In terms of composition, V was found as the most beneficial alloying element increasing hardness and fracture toughness of hot work tool steel; Si, Mn, and Cr increase hardness but lead to reduced fracture toughness, while Mo has the opposite effect. Optimum concentration providing high KIc/HRC ratios would include 0.75 pct Si, 0.4 pct Mn, 5.1 pct Cr, 1.5 pct Mo, and 0.5 pct V, with the optimum heat treatment performed at lower austenitizing and intermediate tempering temperatures.

Deep cryogenic treatment of tool steels

The aim of our research work was to investigate the effect of deep cryogenic treatment on fracture toughness, wear resistance and load-carrying capacity of cold work tool steel and to determine the effectiveness of deep cryogenic treatment depending on the tool steel type and chemical composition. The type and chemical composition of the tool steel considerably affect the way how deep cryogenic treatment changes mechanical, tribological and load-carrying capacity of the tool steel. For lower carbon and higher W and Co containing cold work tool steel properties can be improved for up to 70%, but are very limited in the case of high-speed steel. At high carbon and vanadium contents properties of cold work tool steels can even be deteriorated after deep cryogenic treatment. In terms of abrasive wear resistance and load-carrying capacity increasing the hardness is the most decisive factor.

Optimal fractal dimension on grain structure robot laser-hardened tool steel

A B S T R A C T A R T I C L E I N F O In order to optimize the structure and properties of tool steel, it is necessary to take into account the effect of the self-organization of a dissipative structure with fractal properties at load. Fractal material science researches the relationship between the parameters of fractal structures and the dissipative properties of tool steel. This paper describes the application of fractal dimension in robot laser-hardening specimens. By using fractal dimensions, changes in the structure can be determined because the fractal dimension is a present indicator of the complexities of the sample forms. We hardened tool steel at different speeds and different temperatures. By researching the fractal dimensions of the microstructures of the hardened specimens we could better understand the effects of the parameters of robot cells on the material. We show the experimental results and an analysis of those fractal patterns that occur during robot laser hardening with the different parameters of temperature and speed. Finally, we present the relationship between the fractal dimensions and the parameters of temperature and speed of robot laser hardening. The hardening of various metal alloys showed that when melting occurs, fractal geometry can be used to calculate the fractal dimension. The dependence of the fractal dimension on the hardness was ascertained. This finding is important when we realize that certain alloys mix poorly because they have different melting temperatures but such alloys have a much higher hardness and better technical characteristics.

Investigation of Cutting Forces, Surface Roughness and Tool Wear during Laser Assisted Machining of SKD11Tool Steel

The present work deals with the machining of Tool steel - SKD 11 which is widely used in industries for making dies and molds. It is chosen for its toughness, strength, and hardness maintained up to high temperature. However, the properties of tool steel make it extremely difficult and expensive to machine using conventional approaches. Thermally assisted machining has been found wide spread application in recent years to improve machinability of difficult-to-cut materials. This research paper presents the outcome of an investigation on laser assisted turning of SKD 11 using TiN coated ceramic inserts. Extensive heating studies are carried out to understand the laser–material interaction. The LAM parameters were selected based on the outcome from heating study. In this study, the effect of laser beam on cutting forces, surface temperature, surface roughness and tool wear are analysed over wide range of cutting speeds and feed rate and the results are compared with conventional machining.

Microstructure and tensile properties of 45WCrV7 tool steel after deep cryogenic treatment

Two groups of tool steel properties, high hardness or strength, and high toughness, are important in performance of tool steels. Normally, any increase in hardness or strength occurs at the expense of reduced toughness. However, deep cryogenic treatment may be used to produce advanced tool steel by means of increasing toughness, strength and hardness simultaneously. Twelve sets of specimens were tested; nine of them were deep cryogenic treated and then tempered and 11 underwent double deep cryogenic treatment at the same temperatures. The best results as simultaneous improvement in toughness, hardness and strength were obtained for two sets.

The effect of heat treatment on the mechanical, tribological and load-carrying properties of PACVD-coated tool steel

The limited load-carrying capacity of tool steels greatly restricts the use of hard coatings in forming applications. This can, however, be improved by increasing the substrate's hardness, but especially for hot forging, the fracture toughness and resistance to cracking are equally important. The present work was focused on the possibilities of combining a vacuum heat treatment, a deep-cryogenic treatment and plasma nitriding in order to improve the properties of PACVD-coated tool steel.The investigation included TiCN-coated P/M high-speed steel, with 12 different combinations of the vacuum heat treatment, the deep-cryogenic treatment and plasma nitriding, which were investigated as a way of simultaneously improving the mechanical, tribological and load-carrying properties of tool steel. The results show that for the most demanding forming operations the substrate toughness is far more important than the hardness, especially at elevated temperatures, with just a vacuum-heat-treated steel substrate giving the best support for the top coating.

Effect of Alloying Elements on the Tooling Capabilities of High Speed Steels Fabricated by Powder Metallurgy

Abstract SPM 10 and ASP 2052 alloys fabricated by powder metallurgy have a higher alloying elements content than rolled types. Such higher alloying contents improve the mechanical properties of tool steels and provide a longer tooling life. In this study, the effects of alloying elements and different heat treatments processes on the properties of SPM 10 and ASP 2052 were investigated. Also, the effects of alloying elements and process parameters on the mechanical properties as well as tooling abilities of the specimens were studied. The specimens were characterized by Rockwell hardness tests and the tooling abilities of the specimen were determined by characterizing the number of screws that could be fabricated with specimens. According to the results of the experiments, higher hardness values were obtained at elevated austenitization temperatures. Besides, the presence of Co as an alloying element evolved better hot work properties of the specimens.

Precipitation Behavior of Modified as Cast High Nitrogen Super Hard High‐Speed Tool Steel

AbstractThe properties of high‐speed tool steels can be improved by modifying their chemical composition or the technology of production. Nitrogen alloying is an attractive technology to enhance the mechanical and physical properties of tool steels. In this work, modified super hard high‐speed tool steel was produced through nitrogen alloying and decreasing the level of cobalt content in investigated steels. This work aims to study the effect of nitrogen as alloying element on carbides and carbo‐nitrides precipitates type, shape, and size for investigated steels. From the results obtained from Thermo‐Calc, it was concluded that nitrogen alloying produced large amount of stable austenite, also eutectic carbides precipitates (M6C and M7C3) were stable at room temperature. Transmission electron microscope (TEM) images for traditional grade showed that the as cast structure contains beside the carbides network other single carbides precipitates. While on the other hand the selected area diffraction pattern (SADP) images of nitrogen alloyed grade shows fine carbides and carbo‐nitrides precipitates with more amount of retained austenite in the ferrite matrix, they showed also the presence of the eutectic precipitates as well as the dislocations.

Investigation of influence of laser operation on the structure and properties of tool steel with cladded coatings.

Investigation of influence of laser operation on the structure and properties of tool steel with cladded coatings.

“The Faster the Better” – heat treatment of hot work tool steels

Abstract This article intends to draw attention to the problems and some solutions manufacturers face when using tool steels. Remarkable improvements have been made in the performance of this important steel group within the last decade. Enhanced material properties have been achieved by increasing cleanliness, homogeneity and modification of chemistry as well as a better understanding of heat treatment and operating conditions. These advances have led to increased loading as well as larger dimensions of tools and dies. This increase in size in particular implicates significant challenges to steel making, tool making and heat treatment. The material properties of tool steels are discussed exemplary for hot work tools steels along with a description of typical heat treatment parameters. Attention is paid on the very narrow range of treatment parameters that give desirable material properties.

Influence of Heat Treatment and Thermochemical Processes on the Properties of the Steel X 38 CrMoV 5 3

Abstract In this study, the effects of heat treatments and cooling rates on the properties of the steel X 38 CrMoV 5 3 were investigated. Heat treatments and cooling rates during the steel fabrication processes are critical parameters for the properties of tool steels, since the phases and the lattice structures change respectively. In the experiments, four different heat treatment processes and also, nitriding and carbonitriding processes were applied to specimens made from the investigated steel. For such experiments, two different austenitising temperatures with three different cooling rates were selected and the effects of the process para­meters on the mechanical strength were investigated. Microstructure evaluations were carried out by image analysis and by using a scanning electron microscope. To determine and compare the mechanical properties, Vickers hardness tests and three-point bending tests were applied.

Metallurgical principles of cryogenically treated tool steels—a review on the current state of science

The cryogenic treatment of tool steels has transformed over centuries from black art to science, but the metallurgical principles responsible for increase in wear resistance, tensile strength, toughness, and stability are still disputed. Metallurgists comprehend how tool steels respond to cryogenic treatment, but they also understand that for many years, the cryogenic treatment of tool steels had the reputation of being a quick fix for poor heat treatment practice. During the cryogenic treatment of tool steels, the process modifies the carbon present in the tool steels. However, cryogenic treatment has not been widely adopted by the cutting tools industry due to lack of understanding of the fundamental metallurgical mechanisms and due to the wide variation in reported research findings. In the present paper, an attempt has been made to review the literature on metallurgical changes that occurred during the cryogenic treatment of tool steels to benefit the cutting tools industry. The prominent reasons found to be responsible for improving the mechanical properties of tool steels are transformation of retained austenite to martensite and precipitation of fine carbides.

Evaluation of factors influencing deep cryogenic treatment that affect the properties of tool steels

Deep cryogenic treatment (DCT) of tool steels is used as an additive process to conventional heat treatment and usually involves cooling the material to liquid nitrogen temperature (−196 °C). This kind of treatment has been reported to improve the wear resistance of tools. In this study, the Taguchi method was used to identify the main factors of DCT that influence the mechanical properties and the wear resistance of the powder metallurgically produced cold-work tool steel X153CrVMo12 (AISI D2). Factors investigated were the austenitizing temperature, cooling rate, holding time, heating rate, and tempering temperature. In order to study the significance of these factors and the effect of possible two-factor interactions L 27(3 13), an orthogonal array (OA) was applied to conduct several heat treatments, including a single DCT cycle directly after quenching prior to tempering. The results show that the most significant factors influencing the properties of tool steels are the austenitizing and tempering temperatures. In contrast, the parameters of deep cryogenic treatment exhibit a lower level of significance. Further investigations identified a nearly constant wear rate for holding times of up to 24 h. The wear rate reaches a minimum for a longer holding time of 36 h and increases again with further holding.

Effect of residual austenite on properties of tool steel following shortened treatments in lower bainitic phase

Recent investigations show the possibility of shortened low-cost treatment of chromium alloyed tool steels in the lower bainitic state. But with these treatments just above the martensite start temperature remains still an amount of residual austenite. For better understanding of the reactions due to the transformation of austenite into lower bainite metallographic, studies completed by dilatometric tests have been carried out. Structural characteristics due to applied heat treatment processes are discussed and special changes of specific properties are discussed by example of the steel 100Cr6 (SAE 52100).

P-14 Fatigue Properties of Ion Nitrided Tool Steel

In this study, the authors have investigated and clarified that ion nitriding was able to improve the fatigue properties of tool steel. Three kinds of specimens under the different heat treatment conditions were used in this study. The fatigue test had been performed using a rotating bending fatigue testing machine to investigate the effects of ion nitriding on fatigue properties of tool steel. The fatigue fracture surface was analyzed using a scanning electron microscope (SEM), and hardness distribution was also investigated using a microhardness tester. The fatigue strength and hardness of the heat treated specimen were much greater than those of the non-heat treated specimen. It is considered that the micro structure of the heat treated specimens was refined; and the refined structure reduced fatigue failure and increased hardness of the specimens. According to the results of the fatigue test, the most effective treatment method on improving the fatigue limit was determined in this study. The hardness of the specimens remarkably increased after ion nitriding processing.

Effect of Deep Cryogenic Treatment on Carbide Precipitation and Mechanical Properties of Tool Steel

It is well known that the durability of tool steel could be improved by deep cryogenic treatment. It has been assumed that the increase of service life of tool steel caused by decrease of retained austenite and/or by formation of nano-scale fine η-carbide. But the principles of deep cryogenic treatment remain unclear yet. In this research, to manifest the effect of deep cryogenic treatment on wear resistance, the specimen was emerged in liquid nitrogen for 20 hours for deep cryogenic treatment after austenitizing and the following tempering temperature was varied. The microstructure of specimens was observed using TEM and the mechanical properties and wear resistance were examined. As the tempering temperature increased, the carbides became larger and fine carbides were formed above certain temperature. In the case of deep cryogenic treated specimen, the number of carbides increased while the carbides size was decreased, furthermore, the fine carbide forming temperature was lowered also. It was considered that the deep cryogenic treatment increased the driving force for the nucleation of carbides. As tempering temperature increased, hardness decreased while wear resistance and impact energy increased. The deep cryogenic treated specimens showed this tendency more clearly. It was considered that the wear resistance is affected not only to the hardness but also to the precipitation of fine carbides, and this carbide evolution can be optimized through the deep cryogenic treatment.

Mechanical properties of tool steels with diffusion carbon and nitrocarbon layers

The present paper presents the results of metallographical investigation and wear tests of tool steel grades: hot work steels 4H5W2FS, AMS 6437E and cold work steels ASTM A681, Ch12FS. All surfaces were hardened by the Carbo process (carburising) and by the NiCar process (nitrocarburising). The thermochemical treatment was conducted in powder pack for durations of 6 h (carburising) and of 4 h in the case of nitrocarburising. Wear tests were conducted by the three cylinder cone method. Wear velocity was 0·58 m s−1, unit loads were 50 and 400 MPa, wear path was 3470 m. Oil SAE30 was applied at the rate of 30 drops/min−1. Factors investigated were: morphology, depth and microhardness of the cases obtained, their microstructure, as well as phase composition.

Effect of mixed N and Ar implantation on tribological properties of tool steel

The change of the tribological properties after ion implantation of two kinds of tool steels: chromium—NC11LV and chromium free—N11E was studied. Nitrogen and argon implantations were carried out in different orders at energy 120 keV with the doses 5 × 1 0 17 and 1 × 1 0 17 ions / cm 2 , respectively. Significant improvement of abrasive wear and friction coefficient as well as microhardness of NC11LV steel was observed. The order of mixed implantation influenced on wear and microhardness. The best results were obtained for Ar + implantation prior to N 2 +. Ion beam implantation causes decrease of grain size and increase of microstrain. There is no clear improvement of tribological properties of chromium-free N11E steel after implantation regardless of implanted ions and order of implantation. Microhardness and resistance to abrasive wear usually increases insignificantly but the friction coefficient increases also in all the cases.

Comparison between different test methods for evaluation of galling properties of surface engineered tool surfaces

In forming operations, galling is a tribological process associated with pick-up of formed material by the surface of the tool and subsequent damage of the work material surface. In lubricated operations, it is associated to lubricant film breakdown. Currently the main focus in development of forming tools is on improving their galling resistance, mainly by including new forming tool steels, improving surface finish, and applying surface treatments and coatings. However, in order to qualitatively rank the galling resistance of material couples, a proper test method for galling evaluation is needed. During the years several methods for determining the galling resistance have been reported in the literature. In the present investigation three different test methods were compared and evaluated as to their ability to assess the galling tendencies of coated and un-coated forming tool steel. The study included the pin-on-disc configuration, a modified cylinder-on-cylinder test with a spring loading system, and a new load-scanning test method, which involves two crossed cylinders. It was proved that the load-scanning test rig is both a very simple and the most suitable method to evaluate galling properties of tool steels. It gives the capability to compare different tool steels, tool surface finishes and treatments, and hard coatings in terms of friction level, amount of material transfer, and critical load for galling initiation.