High Speed Steel Powder Research Articles

Компьютерное моделирование процесса горячего изостатического прессования пористых заготовок

Existing mathematical models for the process of HIP porous blanks are based on the solution of approximately differential equations of the equilibrium of quasi-continuous medium. The continual approach is used for computer modeling of the compressible body HIP process. Partial differential equations of motion for a quasi-continuous packing medium and physical equations for a viscous-plastic isotropic porous material subjected to work hardening are taken as the basis for the mathematical model by means of these simultaneous equations. Besides the equations of motion and the rheological equation, the equation of continuity deformation and the equation of heat flow are used. Numerical calculations for additional packing of a high-speed steel powder billet preliminary pressed in the hydrostat are performed. Numerical calculation of the problem for hardening the cylindrical high-speed steel billet with a mild steel shell is done using Lagrange’s method by means of the difference scheme of continuous calculation of the Wilkins’ type. Computer modeling allows to control the process of hardening and changing the form of a porous body during the HIP process.

Characteristics of Electric-Discharge Coatings Fabricated by the Electrodes Made of Electroerosive Powders of High-Speed Steel

Electric-discharge coatings on the samples made of steel 30ХГСА fabricated using a UR-121 installation are investigated. Electrodes for electric-discharge machining are fabricated by hot compacting from the powders prepared by electroerosive dispersing of waste of high-speed steel Р6М5. The microstructure, thickness of the coating layer, and its surface state are studied using modern investigation techniques. Roughness parameters of wares and microhardness of the electric-discharge coating and substrate made of steel 30KhGSA are determined. It is established that the coating microhardness is larger than that one of the substrate by a factor of 2,1, which can be associated with a nonuniform distribution of the particles of high-speed steel in the electric-discharge coating. It is shown that powder materials fabricated by electroerosion dispersing from high-speed steel wastes can be used as the electrode material to fabricate various functional coatings by electric-discharge alloying.

EVALUATION OF WEAR RESISTANCE OF ELECTROSPARK COATINGS FABRICATED USING ELECTROEROSION POWDERS OF HIGH-SPEED STEEL

Characteristics of wear resistance of electrospark coatings deposited using the electrode material made of electroerosion powders of high-speed steel are analyzed. Electrodes for electrospark alloying are fabricated by hot compaction (with the passage of a high- amperage current in vacuum at 950 °C for 3 min) of the powder fabricated by electroerosion dispersing of waste of high-speed steel R6M5. Electrospark coatings with the application of these electrodes were formed on the samples made of steel 30KhGSA using an UR-121 installation. The friction coefficient and wear rate of the sample surface and counterbody were measured using a computer- aided automated friction machine «Tribometer» (CSM Instrument, Switzerland) according to the standard «ball–drive» testing layout.

Effects of Binders System on Sintered Properties of Metal Injection Molding Parts of M2 High Speed Steel

This paper reports on the compatibility of waste rubber binder combined with conventional binder, paraffin wax and local binder, palm stearin for M2 High Speed Steel injection molding in order to obtain the better properties. The feedstock was prepared at a powder loading of 65 vol.% using 22um M2 High Speed Steel powder and the binders consisting of 55wt.% paraffin wax/palm stearin, 21wt.% polyethylene, 14wt.% waste rubber and 10wt.% stearic acid. The specimens were then sintered in vacuum atmosphere within a temperature range from 1200°C to 1260°C. The results shown even the best properties is obtain from the conventional binders, paraffin wax, thus the properties of local binders palm stearin is still comparable and good. The maximum density of paraffin wax binder was 8.095g/cm3 achieved at temperature 1250°C and palm stearin binder was 8.111g/cm3 achieved at temperature 1240°C. Therefore, in term the best strength of paraffin wax was 2351Mpa whilst palm stearin was 2210MPa, both recorded at temperature 1230°C.

The Influence of Sintering Atmosphere for Metal Injection Moulding M2 High Speed Steel

This paper reports on the compatibility of waste rubber as binder for M2 High Speed Steel injection moulding. The feedstock was prepared at a powder loading of 65 vol.% using 22μm M2 High Speed Steel powder and the binders consisting of 55wt.% paraffin wax, 21wt.% polyethylene, 14wt.% waste rubber and 10wt.% stearic acid. The specimens were then sintered in vacuum and 95%N2/5%H2 atmosphere. The sintering in vacuum atmosphere occurred within a temperature range from1200°C to 1260°C, whilst the 95%N2/5%H2 atmosphere was carried out within a temperature range from 1220°C to 1300°C. The effects of the sintering atmosphere and temperature on the physical properties, mechanical properties and microstructure were investigated.

Mechanochemical processing of wastes from high-speed steel machining

The manufacture of cutting plates on the basis of powder produced by the disintegration of wastes from the machining of P6M5 high-speed steel is considered. The use of high-molecular compounds in the processing of waste chips is promising. The performance of plates made from high-speed steel powder is investigated.

High-speed steel powder produced from chip wastes ground in the presence of high-molecular compounds

The properties of high-speed steel powder produced from P6M5 steel wastes dispersed in the presence of a mechanically labile polymer are considered. To obtain maximum density of the product, the time between grinding of the metal and sintering should be minimized.

Technology for processing high-speed steel turnings by powder metallurgy using a high-molecular compound

Plate manufacturing technology is presented for a composite cutting tool from powder prepared by disintegrating high-speed steel machining waste in the presence of a mechanically degradable polymer. Plate operating properties are considered for a composite cutting tool, manufactured from high-speed steel powder.

Sintering Behavior and Mechanical Properties of High Speed Steel Powder Processed In Nitrogen-Based Atmosphere

High speed steel (HSS) is a common material used in the manufacturing of cutting tool and other cutters. In this study, M3/2 HSS had been used to produce cutting tool insert through powder metallurgy (PM) route. The HSS was mixed with iron phosphorus (Fe3P) powders in a tubular mixer for 30 minutes by dry blending. The powder was compacted at pressure of 632 MPa (16 ton) and sintered at temperature range between 1100°C and 1225°C under nitrogen-hydrogen atmosphere. Further work was done through heat treatment process involving austenitising and tempering to improve the mechanical properties of the insert. The properties were determined through hardness testing and transverse rupture strength (TRS).

Spark Plasma co-Sintering of hot work and high speed steel powders for fabrication of a novel tool steel with composite microstructure

The capability to produce a hybrid tool steel with properties that can be modulated on the base of the specific application was investigated. Powder metallurgy (PM) offers the possibility to blend and co-sinter different powders to produce a hybrid material which combines the properties of the base materials. With the aim of producing a new steel with high hardness and good toughness, a hot work tool steel (HWTS) and a high speed steel (HSS) powder were selected. Four blends with different composition (HWTS-HSS: 20%–80%, 40%–60%, 60%–40%, 80%–20%) were produced by spark plasma sintering (SPS) and thermally treated. The influence of composition, particle size distribution and oxygen content was evaluated by the means of density, hardness and apparent fracture toughness of the blends. By selecting powders with a small size and narrow particles size distribution near full dense blends with good mechanical properties can be sintered. Large particles hinder the efficient co-sintering due to the different densification kinetics of the powders. High oxygen content in the base powders does not significantly influences the final density but negatively affects the consolidation process, strongly reducing toughness, particularly of the HWTS.

Preparation and wear properties of discontinuous ceramic fibre reinforced iron alloy by low isostatic press sintering

Low isostatic press sintering (LIPS) behaviour was examined using a mixture of high speed steel powder and discontinuous alumina fibre, and mechanical properties of the obtained LIPS compact were estimated. LIPS is applicable to the composite system in which a reaction gas is generated during sintering because evacuation is continuously carried out during sintering. As the volume fraction of discontinuous alumina fibres is large, pores are formed in the fibre aggregated region, resulting in an increase in porosity. For discontinuous alumina fibre uniformly dispersed composite with no fibre aggregated region, the critical volume fraction of discontinuous alumina fibres exists and depends on both the ratio of the particle diameter of the high speed steel powder to the diameter of the discontinuous alumina fibre and the dispersion morphology of discontinuous alumina fibres. The dispersion of 20 vol.-% discontinuous alumina fibre in high speed steel leads to an increase in wear resistance.

Influence of processing parameters and particle size on the properties of hot work and high speed tool steels by Spark Plasma Sintering

Spark Plasma Sintering (SPS) is a newly developed rapid technique for powder sintering. In this study, consolidation by SPS of high speed steel (AISI M2) and hot work tool steel (AISI H13) commercial powders is investigated. The influence of sintering temperature (900 to 1150°C) and time (0 to 30min) as well as the particle size and distribution is evaluated with respect to final density, hardness and fracture toughness. Properties have been compared with those of samples produced by Hot Isostatic Pressing (HIP).Density increases with increasing temperature up to 1050 and 1100°C for H13 and M2, respectively, a minor influence of time being observed for times longer than 5min. Near fully dense samples (>99.5%) are obtained after sintering at 1100°C for 5min only under uniaxial pressure of 60MPa. Fine powders with a narrow size distribution or, alternatively, powders with a wider particle distribution and sufficiently high fraction of small particles show higher propension towards the achievement of full dense samples. The maximum densification rate occurs at lower temperature for H13 than M2, being negatively affected by the ferrite–austenite transformation during heating and the corresponding resistivity variation. Hardness and fracture toughness are found to increase with increasing density. Comparatively good values are obtained with respect to samples produced by Hot Isostatic Pressing confirming the possibility to produce tools by SPS.

Sintering and Mechanical Properties of AISI M2 High-Speed Steel Powder Molded at Low Pressures

Low compaction pressures of powders result in low die wear, less power consumption and high production rate. The present study aims to investigate compaction, vacuum sintering, and mechanical behavior of AISI M2 high speed steel (HSS) powder cold molded at relatively low pressures (98–392 Mpa). It was found that sintered density rised with compaction pressure, time, and temperature. Full density was achieved in the specimens compacted at 392 Mpa and sintered for 60 min at temperatures between 1250 and 1260°C. Hardness and transverse rupture strength increased to ∼36 HRC and ∼1700 MPa with rising density. The fully dense samples exhibited a slight decrease in mechanical properties with increasing temperature owing to M6C carbide coarsening. X-ray diffraction indicated that M6C (major carbide phase) content in the alloy increased drastically as a result of sintering. It was demonstrated that compaction at a low pressure of 392 MPa could yield high mechanical properties (∼65 HRC and ∼2000 Mpa) in the heat-treated M2 HSS alloy.

Properties of Cold Work Tool Steel Shot Peened by 1200 <I>HV</I>-Class Fe-Cr-B Gas Atomized Powder as Shot Peening Media

Shot peening is widely used for automobile parts such as springs and gears to improve fatigue strength. In general, high hardness media is required for shot peening to targets with high hardness. Recently, shot peening to various tool steels such as cold and hot tool steels and high speed tool steel has been investigated and is used in some applications, and improvements in fatigue strength and die life by the increase of compressive residual stress and hardness at their shot peened surface have been reported.In this study, the properties of cold work tool steel shot peened by Fe-8%Cr-6.5%B (mass%) gas atomized powder (FeCrB powder) with 1200 HV-class Vickers hardness and long life as shot peening media were examined. Quenched and tempered JIS-SKD11 followed by shot peening by FeCrB and high speed steel powder sieved between 45 and 125 μm was used.Vickers hardness and compressive residual stress of the shot peened JIS-SKD11 surface by FeCrB powder were higher than these by high speed steel powder. As a result, JIS-SKD11 shot peened by FeCrB powder showed excellent fatigue property, Charpy impact value and wear resistance property.

冷間工具鋼の諸特性に及ぼす HV 1200級 Fe-Cr-B 投射材を用いたショットピーニングの影響

Shot peening is widely used for automobile parts such as springs and gears to improve fatigue strength. In general, high-hardness media is required for shot peening to high-hardness materials. Recently, shot peening to various tool steels such as cold and hot work tool steels and high speed tool steel has been investigated and is used in some applications, and improvements in fatigue strength and die life by the increase of compressive residual stress and hardness at their shot peened surface have been reported. In this study, the properties of cold work tool steel shot peened by Fe-8%Cr-6.5%B (mass%) gas atomized powder (FeCrB powder) with HV 1200-class Vickers hardness and long life as shot peening media were examined. Quenched and tempered JIS SKD11 followed by shot peening by FeCrB and high speed steel powder sieved between 45 and 125 μm was used. Vickers hardness and compressive residual stress of the shot peened JIS SKD11 surface by FeCrB powder were higher than these by high speed steel powder. As a result, JIS SKD11 shot peened by FeCrB powder showed excellent fatigue property, Charpy impact value and wear resistance property.

Characterization of rapidly solidified powder of high-speed steel

Rapidly solidified particles of high-speed steel were classified into several granulometric fractions ranging from less than 25 μm up to more than 160 μm in diameter and studied by transmission and conversion electron Mossbauer spectrometry. The former was applied at 300, 77, and 5 K. Presence of magnetic and a non-magnetic crystallographic phase was observed. They were identified by X-ray diffraction as ferrite (bcc-Fe) and austenite (fcc-Fe), respectively. In addition, M4C3 and M2C carbides were found. The magnetic phase diminishes in the bulk of the particles bigger than 63 μm (transmission Mossbauer spectroscopy) and/or 80 μm (X-ray diffraction). Its contribution is higher at the surface of the particles (conversion electron Mossbauer spectrometry). The origin of the non-magnetic phase is not changed even at 5 K. Reasonable agreement is achieved between Mossbauer and X-ray diffraction data as far as the fraction of Fe-containing phases is concerned.

ショットピーニング用 1200HV 級 Fe-Cr-B 系ガスアトマイズ合金粉末の開発

Shot peening is a surface treatment effective to obtain compressive residual stress on shot peened surface and to improve fatigue strength, and it is applied to automobile parts such as springs and gears. Based on recent trend for further reduction of automobile parts weight, high hardness of automobile parts will be required more and more through various treatments such as carburizing. In this study to develop gas atomized powder for shot peening with high hardness, high density, high ductility and relatively low cost, Fe-8Cr-6.5B alloy was made by gas atomizing and its various properties were examined. The resultant Vickers hardness was 1260HV, density was 7.4Mg/m3, and no crack initiated near indentation by 1000 g load. No rust was observed in the condition of 343 K-95%RH-96h. Various properties of gas carburized JIS SCM420 with shot peening by developed Fe-8Cr-6.5B powder were compared to that with shot peening by high speed steel powder. JIS SCM420 with Fe-8Cr-6.5B powder shot peening showed higher compressive residual stress at the surface by 110 MPa, higher Vickers hardness (load=100 g) by 60HV and higher fatigue strength by about 100 MPa than that with high speed steel powder shot peening.

ガスアトマイズ法で作製したショットピーニング用 Fe-Cr-B 合金投射材の寿命特性

Shot peening is a surface treatment effective to obtain compressive residual stress on shot peened surface and to improve fatigue strength, and it is applied to automobile parts such as springs and gears. Based on recent trend for further reduction of automobile parts weight, higher hardness of automobile parts is required through various treatments such as carburizing. As hardness of shot peened surface is becoming higher, shot peening media with higher hardness is also desired. In this study, life properties of Fe-8Cr-6.5B gas atomized powder (FeCrB powder) with hardness of about 1200 HV and density of 7.4 Mg/m3 developed for shot peening media was examined. Weight loss of FeCrB powder after shot peening on gas carburized JIS SCM420 target for 24 h was approximately a quarter of that of the high speed steel powder. High hardness of FeCrB powder is thought to suppress deformation at collision to the target and to prevent crack initiation. Furthermore, hardness change during shot peening operation is smaller than that of high speed steel powder.

Microstructural characterisation of vacuum sintered T42 powder metallurgy high-speed steel after heat treatments

High-speed steel powders (T42 grade) have been uniaxially cold-pressed and vacuum sintered to full density. Subsequently, the material was heat treated following an austenitising + quenching + multitempering route or alternatively austenitising + isothermal annealing. The isothermal annealing route was designed in order to attain a hardness value of ∼50 Rockwell C (HRC) (adequate for structural applications) while the multitempering parameters were selected to obtain this value and also the maximum hardening of the material (∼66 HRC). Microstructural characterisation has been carried out by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The microstructure consists of a ferrous (martensitic or ferritic) matrix with a distribution of second phase particles corresponding to nanometric and submicrometric secondary carbides precipitated during heat treatment together with primary carbides. The identification of those secondary precipitates (mainly M 3C, M 6C and M 23C 6 carbides) has allowed understanding the microstructural evolution of T42 high-speed steel under different processing conditions.

Properties of double dispersed tool steels

The aim of this study was to develop a new tool material, which combines the toughness of Hot-Work Steel (HWS) with the wear resistance of High-Speed Steel (HSS). This has been realised via powder metallurgy by blending HWS and HSS powders. The blend, which may contain up to 30 vol.% of high-speed steel powders (grain size 150 microns), is subjected to Hot Isostatic Pressing (HIP). This results in a microstructure that shows a double dispersion of coarse HSS clusters with dispersed small carbides (< 5 microns) in a martensitic HWS matrix without carbides. The new materials can be treated to produce hardness levels of between 40 and 60 HRC. The materials were examined with respect to their wear resistance and fracture toughness and the results obtained were correlated to the microstructure. It is shown that the wear rate of the double dispersed material decreases as the HSS content increases without causing a significant reduction in fracture toughness.