PM High Speed Steels Research Articles

Supersolidus Sintering of Cr Prealloyed Steels by Inductive Heating

AbstractFor powder metallurgy products, high density is an essential requirements to obtain maximum mechanical properties. Here, supersolidus liquid phase sintering (SSPLS) is an effective means to attain high sintered density, as known from PM high speed steels. In the present work it is shown that this technique can also be applied to Cr prealloyed low alloy steel grades. Supersolidus sintering through indirect heating requires precise control of temperature and also the atmosphere, to avoid uncontrolled changes of the carbon level. Higher C contents are beneficial here since they enable lower temperatures and result in wider temperature windows for sintering. The temperatures necessary for SSLPS at moderate C levels are fairly high for standard sintering furnaces, therefore induction sintering was studied in this work. It showed that, as was to be expected, also here precise temperature control is required, but for any carbon level tested a sintering temperature could be identified that yielded high sintered density and good shape retention. The high density attained, in combination with the very high temperatures, results in pronounced grain growth, this process no more being inhibited by the presence of pores, which is undesirable but can however be remedied by suitable heat treatment.

Effects of austenitizing temperature on microstructure and mechanical property of a 4-GPa-grade PM high-speed steel

Effects of austenitizing temperature on the microstructure and mechanical property of a high-strength PM high-speed steel were systematically investigated using a series of heat treatments in the temperature range of 1070–1180 °C. Results showed that the optimal austenitizing temperature to obtain the desired combination of high compressive strength of 3838 MPa and high ductility of 29.7%, the optimal austenitizing temperature was 1180 °C. A maximum strength of 3870 MPa and a fracture strain of 22.7% was obtained by austenitized at 1120 °C. It is evident that the size distribution and carbide contents of both VC and Fe3W3C can be significantly changed by heat treatment and triple tempering resulted in slight decline in the amount of cracked carbides. Fractography showed that more broken particles of Fe3W3C carbide was observed than that of the VC particles in fractured specimens.

Effect of Chemical Composition and Heat Treatment Parameters on the Structure and Properties of Vanadis 23 and Vanadis 30 PM High-Speed Steels

The paper deals with the assessment of the effect of content of cobalt and cryogenic treatment on mechanical properties and structure of Vanadis 23 and Vanadis 30 PM high-speed steels. The studied characteristics are evaluated after conventional heat treatment (quenching and multiple tempering) and also when deep cryogenic treatment at -196°C/4 hours was inserted between quenching and tempering. The mechanical properties are assessed by a three-point bending flexural test and by measurement of the hardness. Metallographic analysis is performed using an energy dispersive spectrometer (EDS) and the scanning electron microscope (SEM).

Development of Powder Metallurgy High Speed Steel

High speed steels (HSS) have been widely used worldwide. This paper introduced some research results of high speed steels via Powder Metallurgy process. High speed steels AHPT15 (W12Cr4V5Co5 ) were investigated via gas atomization, hot isostatic pressing, hot working and heat treatment processes. Microstructure of the steels, precipitation of carbides and the influence of nonmetallic inclusions on mechanical properties of the steels were investigated. PM HSS showed fine and uniform microstructure and exhibited excellent toughness and wear resistance, with bend strength up to 3500 MPa and hardness up to 68.0 HRC.

PM tool steels push the edge in fatigue tests

Austrian researchers fatigue tested PM cold work steel and high speed steels and found that they had remarkable fatigue resistance compared with similar conventional ingot steels. The results they obtained resembled those for high strength bearing and spring steels and they concluded that fatigue limits for these PM tool steels did not exist…

高靱性・高耐食粉末ハイスSPMR8 の開発

高靱性・高耐食粉末ハイスSPMR8 の開発

분말고속도공구강을 활용한 베어링 레이스 열간 단조 금형의 수명 및 기계적 특성

P/M high speed steel (1.26% C, 4.42% Cr, 6.54% W, 4.92% Mo, 3.21 % V, 8.77% Co, bal. Fe) was applied to hot former die. It showed that the die life became 2.7 times higher than that of cast/wrought SKH 55 tool steel which is commercially used. The increase of die life was corresponding to the improved hardness and transverse rupture strength of PM high speed steel due to the finer grain and carbide as well as the uniform carbide distribution. The P/M high speed steel with the promoted die life could be an alternative to the conventional SKH55.

Characterization and Sinterability Study of P.M. High-Speed Steel Obtained by Water Atomization

The paper presents studies about reducing the sintering temperature of PM High-Speed Steel obtained by water atomization. The powder was characterized to proceed with compaction and sintering at different temperatures between 1140-1220°C in different atmospheres: nitrogen (N2), nitrogen-hydrogen-methane (N2/H2/CH4) and vacuum. It is described the experiment in able to increase hardness by a quenching and tempering heat treatment that was carried out on sintered samples at 1140°C in vacuum atmosphere at 1200°C in N2/H2/CH4.

Transverse Rupture Strength of M3:2 High Speed Steel Produced through Conventional Casting and Powder Metallurgy Techniques

The main aim of this work is to study the influence of the heat treatment on the transverse rupture strength of three M3:2 high speed steel obtained by differents techniques. PM Sinter 23 obtained by hot isostatic pressing (HIP) of gas atomized powders, a vacuum sintered high speed steel obtained by uniaxial cold compaction and liquid phase sintering of M3:2 water atomized powders and a conventional (cast to ingot and hot work) VWM3C were submitted to hardening in order to determine the influence of this treatment on the transverse rupture strength. The two PM high speed steels and the conventional one were submitted to heat treatment of hardening with austenitizing temperatures of 1140, 1160, 1180 and 1200 °C and tempering at 540 and 560 °C. The effectiveness of the heat treatment was determined by hardness tests (Rockwell C hardness). The microstructure was evaluated by scanning eletronic microscopy (SEM). At least five samples of these three high speed steels were manufactured, austenitized, quenched and tempered as described above and fractured in three point bending tests in order to evaluate the influence of this treatment on the transverse rupture strength (TRS).

Critical assessment of computational thermodynamics in the alloy design of PM high speed steels

Abstract The experimental powder M42HVIG is used to illustrate how the adequate selection of the constituent phases involved in the calculation of multicomponent phase diagrams is a key factor for success in the computer-aided alloy design of highly sinterable high speed steel compositions.

Influence of Hob Materials on Behavior of Crater Wear of Hob in Dry Hobbing (Fundamental Experiments Using Coated Fly Tools without Coating on the Rake Face)

This paper investigates the influences of various high-speed steel hob substrates coated with (Al, Ti) N film, which are no coating on the rake face by grinding, on a behavior of crater wear mainly, flank wear and finished surface roughness in dry hobbing. Experiments were carried out using fly tools, which were made of normal high speed steels (HSS) and powdered metal high-speed steels (PM HSS). As a consequence, an interesting result was obtained that the crater wear with the M 34 HSS tool is smaller than that with the all PM HSS tools tested at a cutting speed of 117 m/min. At a high cutting speed of 159 m/min, though a failure took place at a tip of cutting edge in some HSS and PM IISS tools, a SK II 51 and a corresponding to SKH 55 HSS tools have no failure, and they are effective for the crater wear. The corresponding to SKH 55 tool, M 34 tool and the PM-HSS tools containing high vanadium and high cobalt are suitable in terms of the flank wear and the surface finished, irrespective of the change in the cutting speed.

Computer aided design of PM high speed steels for vacuum and nitrogen atmospheres

Computer aided alloy design has been used to develop new highly sinterable alloys in order to fulfil the requirements for robust processing of powder metallurgy high speed steels. Three alloys (M35IG, AR-K2 and M42HVIG) have been designed and subsequently analysed in terms of the expected sintering behaviour, atmosphere interaction and microstructural features. Predicted optimum sintering temperatures are 1200°C for the vacuum sintered M35IG alloy and 1150°C for the AR-K2 and M42HVIG alloys sintered under a 90N2+9H2+ 1CH4 atmosphere. On the other hand, the expected sintering windows exceed 10°C for all the alloys and the sensitivity to small compositional changes has been minimised guaranteeing the robust processing requirements. Additionally, sintering temperatures of 1150°C allow processing in continuous belt furnaces with the inherent interest for the industrial environment. Thermo-Calc software and the TC-Fe2000 database have been used to obtain the different calculations on the multicomponent systems.

Effects of cobalt, niobium and titanium on PM high-speed steels: J. Dagmar et al. (Slovak Academy of Sciences, Ko ice, Slovak Republic.)

Effects of cobalt, niobium and titanium on PM high-speed steels: J. Dagmar et al. (Slovak Academy of Sciences, Ko ice, Slovak Republic.)

Effect of niobium on structure and properties of PM high-speed steels : H. Chung et al. (Ajou University, Gyunggi, Korea)

Tools and dies used in hot metal forming are exposed to very demanding contact conditions, including elevated temperatures, high contact pressures and abrasive flow of work material, which lead to different types of tool damage. However, the most critical ones are wear and fatigue fracture. As the focus shifts toward the use of new lightweight high-strength materials, also requirements on tool properties are becoming more demanding. This requires use of surface engineering techniques like nitriding and PACVD coating and proper balance between hardness and fracture toughness. Vacuum heat treatment allows the optimization of the tool steel microstructure, which may result in increased fracture toughness while maintaining or even increasing hardness, which enhances possibilities of using coated forming tools.The aim of this work was to investigate the effect of austenitizing and tempering temperature on properties of AISI H11 hot work tool steel, including fracture toughness and hardness and how these properties effect on wear resistance and load-carrying capacity of plasma nitrided and PACVD-coated tool steel. Results indicate that through optimized vacuum heat treatment and surface engineering resistance of tool steel can be greatly improved. Increasing core hardness improves the resistance of nitrided AISI H11 tool steel to abrasive wear, but sufficient level of fracture toughness needs to be obtained first. Change in fracture toughness/hardness ratio has up to 40% influence on wear resistance. On the other hand, galling resistance mainly depends on the surface condition, with plasma nitrided surface without compound layer providing the very best results. Although TiN/TiB2 coating has no beneficial effect on galling resistance, it gives up to two orders of magnitude better wear resistance than nitride surface. However, for proper coating support high core hardness needs to be provided.

Co 함량이 다른 분말고속도공구강의 제조 및 기계적 특성

P/M high speed steels with various Co contents were fabricated by gas atomization and Canning/HIP process. As Co content in P/M high speed steel increased, hardness, transverse rupture strength and yield strength in compressive testing increased due to solid solution hardening of Co in matrix. Especially, PM high speed steels with Co have high deformation resistance to repeated compressive loading.

Improved anti-galling with PM high-speed steels with added nitrogen

Improved anti-galling with PM high-speed steels with added nitrogen

Processing of PM high-speed steel by mould casting with thermosetting binder

Processing of PM high-speed steel by mould casting with thermosetting binder

The Structure and Properties of PVD Coated PM High-Speed Steels

The Structure and Properties of PVD Coated PM High-Speed Steels

High-speed steels and high-speed-steel based composites

Research on PM high-speed steels and their composites started at INETI in 1984. The PM route adopted has been either vacuum or atmosphere sintering of water atomised powders compacted to shape. A wide range of equipment covers the several steps of this processing route water atomisation, compaction (uniaxial or isostatic), sintering, heat treatment and characterisation (microstructure and mechanical properties). This paper presents results obtained in the current research activity on these materials at INETI in the frame of European Community (EC) contracts and also in collaboration with some Portuguese industries (tool manufacturers).

Influence of atmosphere on debinding and sintering of PM high speed steels: M.Miskovicova et al. (Inst. of Materials Research SAS, Slovak Republic.)

Influence of atmosphere on debinding and sintering of PM high speed steels: M.Miskovicova et al. (Inst. of Materials Research SAS, Slovak Republic.)