Powder Metallurgy Tool Research Articles

Investigating the performance evaluation of Cu-Cr tool fabricated by powder metallurgy during electrical discharge machining of EN9 steel

Purpose The purpose of this study is to explore the machining characteristics of electrical discharge machining (EDM) when a tool is fabricated using powder metallurgy. Because pure Cu tools obtained using conventional machining pose problems of high tool wear rate, tool oxidation causes loss of characteristics in tool shape. Design/methodology/approach The research investigation carried out experiments planned through Taguchi’s robust design of experiments and used analysis of variance (ANOVA) to carry out statistical analysis. Findings It has been found that copper and chromium electrodes give less metal removal rate as compared to the pure Cu tool. Analytical outcomes of ANOVA demonstrated that MRR is notably affected by the variable’s polarity, peak current, pulse on time and electrode type in the machining of EN9 steel with EDM, whereas the variables pulse on time, gap voltage and electrode type have a significant influence on EWR. Furthermore, the process also showed that the use of powder metallurgy tool effectively reduces the value of SR of the machined surface as well as the tool wear rate. The investigation exhibited the possibility of the use of powder metallurgy electrodes to upgrade the machining efficiency of EDM process. Research limitations/implications There is no major limitation or implication of this study. However, the composition of the powders used in powder metallurgy for the fabrication of tools needs to be precisely controlled with careful control of process variables during subsequent fabrication of electrodes. Originality/value To the best of the authors’ knowledge, this is the first study that investigates the effectiveness of copper and chromium electrodes/tools fabricated by means of powder metallurgy in EDM of EN9 steel. The effectiveness of the tool is assessed in terms of productivity, as well as accuracy measures of MRR and surface roughness of the components in EDM machining.

Effect of vibration and cutting zone temperature on surface topography during hybrid cooling/lubrication assisted machining of Vanadis 10

Abstract New alloy materials developed to meet the increasing technological needs of people come into our lives with some difficulties in terms of machinability. New cooling and lubrication techniques have been developed to facilitate the workability of such difficult-to-process materials and protect the world ecologically and the quality of the produced product. The workpiece used in this study, Vanadis 10 SuperClean, is a high vanadium alloyed powder metallurgy tool steel offering a unique combination of excellent abrasive wear resistance in combination with a good chipping resistance. The present study investigated the effects of dry, cryo, and CryoMQL cutting conditions on cutting tool vibration amplitude, cutting temperature, surface roughness, tool wear, and tool life in turning of Vanadis 10 tool steel used in the automotive industry. The experiments were performed using TiCN/Al2O3/TiN coated cemented carbide tools and cutting parameters as the constant depth of cut (1 mm), feed rates (0.08, 0.1, 0.12 mm rev−1), and cutting speeds (80, 100, 120 m min−1). The results obtained from experiments showed that spraying liquid nitrogen into the cutting zone provided significant improvements on cutting temperature, tool wear, cutting tool vibration amplitude, and surface roughness. The best results in terms of all output were achieved in the CryoMQL cutting environment. CryoMQL environment has reduced surface roughness up to 65.03 %, flank wear 56.99 %, cutting temperature 32.77 %, and cutting tool vibration amplitude up to 42.76 % compared to dry machining.

INVESTIGATION OF CORROSION AND ADHESION BEHAVIORS OF BORONIZED ASP® 2012 STEEL

Tool steels are extensively used in sheet metal forming dies in order to prolong the life of dies and reduce the cost of production. Powder metallurgy tool steels are also alternatively preferred because of their low-risk metallurgical behavior owing to their compositions by which bulk steel would be difficult to produce, such as high amount of carbides or high alloying elements. Such advantage is desired if the steel has a narrow range of fine grain sizes and is less metallurgically affected by the heat treatment process due to having large surface area of fine grains. In this study, ASP® 2012 powder metallurgy steel containing high amounts of Si, Cr, Mo and W was selected for boronizing by the boron-giving thermochemical process. The boride layers on the surface of ASP® 2012 tool steel were metallographically characterized by various characterization techniques including adhesion strength test, SEM and XRD. The effects of corrosion kinetics and chemical composition of steel on the amount and types of boride layers formed on P/M steel of ASP® 2012 after powder-pack boriding were investigated. The results indicate that, according to the Rockwell-C indentation test, the best adhesion in the boride layer was obtained in samples borided at 850°C for 4 h, while the worst adhesion was obtained in ASP® 2012 steel boronized at 950°C for 4 h. Corrosion rates of boronized ASP® 2012 steel were decreased compared to nonboronized ASP® 2012 steel.

CRUCIBLE CPM S110V

Abstract Crucible CPM S110V is a high alloy martensitic stainless tool steel produced by the Crucible Particle Metallurgy (CPM) process. Crucible CPM S110V contains a high volume fraction of both vanadium-rich and niobium-rich primary alloy carbides for exceptionally good wear resistance compared to other commercially available powder metallurgy tool steels. It also offers better corrosion resistance than AISI 440C or Crucible CPM S90V. The CPM process results in a fine and uniform carbide distribution in Crucible CPM S110V compared to conventionally produced high alloy tool steels, which results in relatively good machining, grinding, and toughness characteristics despite the high alloy content. This datasheet provides information on composition, microstructure, and hardness. It also includes information on corrosion resistance and wear resistance as well as heat treating, machining, and powder metal forms. Filing Code: TS-830. Producer or source: Crucible Industries.

Effect of Different Heat Treatments on Tensile Properties and Unnotched and Notched Fatigue Strength of Cold Work Tool Steel Produced by Powder Metallurgy

The present study investigates the effect of two heat treatments on the microstructure, the tensile and the fatigue properties of a powder metallurgy tool steel that has undergone two heat treatments: quenching and multiple tempering (conventional for powder metallurgy tool steel), and quenching and multiple tempering with an intermediate cryogenic step at −80 °C (new solution). The findings of the research indicated that the new heat treatment promotes the development of a homogeneous distribution of carbides in the martensitic matrix, with an increase of about 10% in tensile strength and about 7% in elongation to failure. This combination of exceptional strength with a high degree of toughness leads to an improvement in the fatigue behaviour of the steel, which exhibits a higher unnotched and notched fatigue strength (about 15% and 25% respectively) and a lower fatigue notch factor (about 15%) compared to conventionally heat-treated steel. These results highlight that the powder metallurgy tool steel, with the new heat treatment, could be a viable option for the production not only of tools and dies, but also for high-performance automotive components, including even those with complex geometries, such as camshafts or crankshafts.

Effect of Eco‐Friendly Minimum Quantity Lubrication in Hard Machining of Vanadis 10: A High Strength Steel

Vanadis 10 SuperClean is a high vanadium alloyed powder metallurgy tool steel offering a unique combination of an excellent abrasive wear resistance in combination with a good chipping resistance. In this study, the effects of the eco‐friendly (100% biodegradable plant‐based) Minimum Quantity Lubrication (MQL) system on the cutting temperature, cutting tool vibration amplitude, tool wear, average surface roughness, and tool life in the turning of Vanadis 10 steel (50 HRC) used in the automotive industry are investigated. In the experiments, TiCN/Al2O3/TiN‐coated cemented carbide tools are used. Experimental results showed that, compared to Dry machining, MQL produced remarkable improvements in terms of cutting temperature, cutting tool vibration amplitude, tool wear, and surface roughness. In addition, the Taguchi experimental design, ANOVA, and linear and quadratic regression analyses are applied to the experimental data. The statistical analysis found the most effective parameter on average surface roughness to be the cutting environment (86.31%). It is determined that the cutting speed was the most effective on vibration amplitude and tool wear (46.22% and 32.41%). The correlation coefficients for the linear and quadratic regression analysis were 0.9 and 0.95, respectively.

Surface characteristics investigation of tool steel machined by powder metallurgy tool in EDA

Use of sintered tool electrodes for surface alloying by electrical discharge alloying (EDA) process has emerged as an alternating machining option with a view to improve surface properties. The present study identifies the appropriate process parameter settings to machine high carbon tool steel (En31) for higher surface finish using copper-manganese (Cu–Mn) powder metallurgy (PM) tool electrode. The effect of six different process parameters was evaluated using Taguchi’s experimental design and analysis of variance. The characterization of the surface alloyed with Mn and carbon was done by micro-hardness measurement, scanning electron microscope (SEM), atomic force microscope (AFM), energy dispersive x-ray spectrum (EDX) quantitative analysis and x-ray diffraction (XRD) technique. Also, the comparison was done with the surface machined using conventional Cu electrode. The surface machined with Cu-Mn PM tool electrode was found to be significantly alloyed with Mn and carbon having fewer micro-voids and no micro-cracks. Nano-size hillocks and valleys were found on the alloyed surface that is expected to improve the oil retention property of the surface. Presence of phases like Mn5C2 and Fe3C in the alloyed surface resulted in 95% and 33% higher microhardness than the base material and surface machined with conventional Cu electrode, respectively.

Microstructural Analysis of Powder Metallurgy Tool Steels in the Context of Abrasive Wear Behavior: A New Computerized Approach to Stereology

The present work describes a new methodology designed to characterize the microstructures of tool steels containing carbide hard phases, with the focus set on their abrasive wear resistance. A series of algorithms were designed and implemented in MATLAB® to (i) recognize each of the features of interest, (ii) measure relevant quantities and (iii) characterize each of the phases and the alloy in function of attributes usually neglected in wear description applications: size distribution, shape and contiguity of the hard phases. The new framework incorporates new parameters to describe each one of these attributes, as observed in SEM micrographs. All three aforementioned stages contain novel contributions that can be potentially beneficial to the field of materials design in general and to the field of alloy design for severely abrasive environments in particular. Models of known geometry and micrographs of different powder metallurgy steels were analyzed, and the obtained results were compared with the obtained by the linear intercept method. The relation between the new parameters and the ones available in the scientific literature is also discussed.

Investigation of Micro-Hardness in Electrical Discharge Alloying of En31 Tool Steel with Cu–W Powder Metallurgy Electrode

In the present study, efforts have been made to identify favorable conditions to enhance surface micro-hardness (MH) of En31 tool steel using Cu–W tool manufactured by powder metallurgy (PM) in electrical discharge alloying (EDA) process. Taguchi method was followed to get combination of six process variables for achieving best MH. Peak current emerged as the major factor to influence the MH of the alloyed layer, although tool polarity, percentage of alloying element in PM tool, pulse on-time, duty factor and discharge voltage were also found significant. MH measurement, scanning electron microscopy, optical microscopy, EDS and XRD were carried out to find micro-geometrical, micro-structural, chemical and mechanical changes in the machined surface. Under favorable conditions for MH, noteworthy enhancement in percentage of carbon and tungsten was observed. The presence of hard tungsten carbide ( $$\hbox {W}_{2}\hbox {C}$$ ) and cementite ( $$\hbox {Fe}_{3}\hbox {C}$$ ) on the machined surface were related to the observed substantial increase in MH ( $$\sim 150\%$$ ). Results indicated that MH improvement can be carried out devoid of any disadvantageous effect on surface quality using EDA process.

Hard and wear resistance TiC-composite coating on AISI 1020 steel using powder metallurgy tool by electro-discharge coating process

TiC–Cu tool electrode prepared by the powder metallurgy route has been used to deposit TiC coating on AISI 1020 mild steel by the electro-discharge coating (EDC) process. Different ratios of TiC and Cu were considered to make a tool electrode that enables to produce acceptable quality coating. The effect of peak current and pulse duration during the EDC process was analyzed for the deposition rate and surface characteristics of the coating. The microhardness of the coated surface was measured by Vickers microindentation tester and microstructure of the deposited layers was studied by scanning electron microscopy (SEM). The elements present in the coating were analyzed through energy-dispersive spectroscopy (EDS), and the compounds formed during the coating process were identified by the XRD technique. The wear rate of the coated samples was measured through ball-on-disc-type sliding wear test against WC–Co ball. Analysis of the experimental results revealed that a higher peak current during the EDC process augmented the microhardness and wear resistance of the coating.

Parameters Optimized Specifying for EDM with PM/Conventional Electrodes on M2 Tool Steel using Taguchi and TOPSIS

Objectives: The scope of this experimental work of electrical discharge machining (EDM) process with and without the addition of abrasive powder while executed on M2 tool steel for the advancement in surrounding safety factors to meliorate the surface quality. Methods/Statistical Analysis: Taguchi’s L36 mixed orthogonal array is used after identification of most appropriate six input parameters (polarity, electrode type, concentration of abrasive, discharge current, and gap voltage and duty cycle) for maximum MRR and minimum TWR, and SR. Findings: To recognize the significant factors ANOVA is used and TOPSIS determine the 10.47% overall improvement in all responses with the optimal level of process parameters after confirmatory test. Energy dispersive X-ray (EDS) and Scanning electron microscope (SEM) analysis applied to examine the surface quality. Application/Improvements: This study finds the downfall of titanium from powder metallurgy tool electrode (CuTi) and deposition of aluminium material from PMEDM may also be implemented to improve the method of computation and precision.

Micro-hardness evaluation for surface alloying of H11 die steel with Cu–Cr–Ni powder metallurgy tool in electrical discharge machining

Electrical discharge machining is a non-conventional material removal process; recently, efforts have been made to use it as a surface alloying/modifying method. This study investigates and compares the micro-hardness of the surface machined by electrical discharge machining process using composite tool electrode (copper–chromium–nickel) manufactured by powder metallurgy and conventional copper tool. Design of experiment is used to find the best level of process parameters in order to achieve high micro-hardness. The machined surfaces are subsequently analyzed using different techniques like scanning electron microscopy, X-ray diffraction and energy-dispersive spectroscopy to ascertain the surface characteristics. Results indicate that the micro-hardness of the alloyed surface formed by powder metallurgy tool electrode is improved by 96.3% as compared to base material and 65.7% as compared to the surface machined by conventional copper electrode. Energy-dispersive spectroscopy of the surface machined using powder metallurgy electrode confirms significant material migration from tool and dielectric to the machined surface. The X-ray diffraction shows the formation of cementite (Fe3C), intermetallic compound of iron, chromium and nickel (FeCrNi) and chromium carbide (Cr7C3) on the surface machined using powder metallurgy electrode.

R-Curve Approach to Describe the Fracture Resistance of Tool Steels

This work addresses the events involved in the fracture of tool steels, aiming to understand the effect of primary carbides, inclusions, and the metallic matrix on their effective fracture toughness and strength. Microstructurally different steels were investigated. It is found that cracks nucleate on carbides or inclusions at stress values lower than the fracture resistance. It is experimentally evidenced that such cracks exhibit an increasing growth resistance as they progressively extend, i.e., R-curve behavior. Ingot cast steels present a rising R-curve, which implies that the effective toughness developed by small cracks is lower than that determined with long artificial cracks. On the other hand, cracks grow steadily in the powder metallurgy tool steel, yielding as a result a flat R-curve. Accordingly, effective toughness for this material is mostly independent of the crack size. Thus, differences in fracture toughness values measured using short and long cracks must be considered when assessing fracture resistance of tool steels, especially when tool performance is controlled by short cracks. Hence, material selection for tools or development of new steel grades should take into consideration R-curve concepts, in order to avoid unexpected tool failures or to optimize microstructural design of tool steels, respectively.

Characterisation of TiC layers deposited using an electrical discharge coating process

Electrical discharge machining (EDM) is a non-conventional, high-accuracy machining process for the manufacture of complex shapes, regardless of hardness of the workpiece. There is interest to develop the EDM technique for coating or surface modification by using a powder metallurgy (PM) tool electrode and/or added powder suspended within the dielectric fluid. We report on the EDM deposition of TiC coatings onto stainless steel, using either Cu or TiC electrodes, with and without Ti powder in the working oil. EDM processed layers exhibited hardness values ∼ 3-4 times higher than the substrate, emphasising the ability of EDM to impart improved mechanical performance to the surface of austenitic stainless steel.

Nano-Scale Friction of Multi-Phase Powder Metallurgy Tool Steels

Friction is a fundamental phenomenon in tribology involving complex mechanisms between the contacting surfaces. Measurements of friction are often made using devices with substantially larger contact area than dimensions corresponding to microstructural features of the materials. Hence, for multi-phase materials, influence of particular microstructural constituents is not resolved. In the present work, a tribometer with a contact area in the nanoscale range was used to map friction for different types of tool steels with different chemical-and phase composition. Owing to the small tip radius, frictional characteristics of primary carbides and the steel matrix were measured and compared. Depending on chemical composition, a difference was observed where the coefficient of friction was approximately twice higher for the steel possessing highest coefficient of friction, including both carbides and the steel matrix.

Surface Roughness and Microhardness Evaluation for EDM with Cu–Mn Powder Metallurgy Tool

In the present research, composite electrode (Cu–Mn) manufactured through powder metallurgy has been used to machine hot die steel (H11) by electrical discharge machining (EDM) process with the aim of inducing manganese and carbon into the machined surface. Such alloying is expected to improve the microhardness and other surface characteristics. Best level of process parameters for better surface finish and high microhardness are found using Taguchi method. Six processing parameters are considered and their significance is investigated by analysis of variance. Techniques like energy dispersive spectroscopy, scanning electron microscopy, and X-ray diffraction are used to ascertain the surface characteristics. Surface machined at optimum process conditions for microhardness shows 93.7% improvement due to formation of cementite, ferrite and manganese carbide phases. Surface roughness having Ra value of 3.11 µm has been achieved.

Gigacycle Fatigue Behaviour of Sintered WC-Co Hardmetals Investigated by Ultrasonic Resonance Testing

Hardmetals, manufactured from powders by pressing and sintering, are the most important tool materials in service today. In many applications, such as milling or percussion drilling, they are subjected to fatigue with considerable loading cycle numbers. In the present study, the fatigue behaviour of hardmetals in push-pull loading was investigated up to Nmax= 1010using ultrasonic resonance fatigue testing. It showed that with all hardmetal grades investigated there is no fatigue “limit”, i.e. a horizontal branch of the S-N curve, but a consistent drop of the curve up to maximum N. Crack initiation was found to occur predominantly microstructure-controlled, as compared to defect controlled as typical for powder metallurgy tool steels.Keywords: gigacycle fatigue, WC-Co hardmetals, ultrasonic fatigue testing, fatigue limit

New Indicators Of Burnished Surface Evaluation – Reasons Of Application

Abstract Modern production technology requires new ways of surface examination and a special kind of surface profile parameters. Industrial quality inspection needs to be fast, reliable and inexpensive. In this paper it is shown how stochastic surface examination and its proper parameters could be a solution for many industrial problems not necessarily related with smoothing out a manufactured surface. Burnishing is a modern technology widely used in aircraft and automotive industries to the products as well as to process tools. It gives to the machined surface high smoothness, and good fatigue and wear resistance. Every burnished material behaves in a different manner. Process conditions strongly influence the final properties of any specific product. Optimum burnishing conditions should be preserved for any manufactured product. In this paper we deal with samples made of conventional tool steel – Sverker 21 (X153CrMoV12) and powder metallurgy (P/M) tool steel – Vanadis 6. Complete investigations of product properties are impossible to perform (because of constraints related to their cost, time, or lack of suitable equipment). Looking for a global, all-embracing quality indicator it was found that the correlation function and the frequency analysis of burnished surface give useful information for controlling the manufacturing process and evaluating the product quality. We propose three new indicators of burnishing surface quality. Their properties and usefulness are verified with the laboratory measurement of material samples made of the two mentioned kinds of tool steel.

Surface Alloying by Powder Metallurgy Tool Electrode Using EDM Process

In this study, electrical discharge alloying (EDA) is used to modify the surface of high carbon steel En31 with the help of tool electrode (Copper-Chromium-Nickel) manufactured by powder metallurgy (PM) process. The effect of Electrical Discharge Machining (EDM) parameters on micro-hardness during surface alloying is studied. Design of experiment (DOE) using Taguchi method and L18 orthogonal array is used to find the best level of process parameters in order to achieve high micro-hardness. Six processing parameters; including tool polarity, percentage of alloying element in tool, peak current, pulse on-time, duty factor, and voltage, are considered and their significance is investigated by analysis of variance (ANOVA). Experimental results show the increase in micro-hardness of the machined surface by 139.7% as compared to the base material. Additionally, techniques like Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) are used to analyze the change in composition of alloying elements and phases of the machined surface. It is concluded that the increase in micro-hardness is due to the formation of carbides containing chromium in the alloyed layer.

Influence of tool steel microstructure on friction and initial material transfer

An investigation was conducted to study the influence of tool steel microstructure on initial material transfer and friction. Two different powder metallurgy tool steels and an ingot cast tool material were tested in dry sliding against 1.4301, 1.4162, Domex 355 MC and Domex 700 MC sheet materials. It was found that tool steel hard phase heights influence initial material transfer and friction. The coefficient of friction increased with decreasing tool steel hard phase heights at 50N normal load and initial material transfer occurred around protruding hard phases. At higher load of 500N the sheet material adhered to both the tool steel matrix and hard phases. Coefficient of friction decreased with increasing proof strength of the sheet material at 500N normal load.