Sintering Of High Speed Steel Research Articles

Sintering of AISI M3:2 High Speed Steel – Part II

Liquid phase sintering of high speed steels seems to be a cheaper processing route in the manufacturing of tool steels if compared to the well-known and expansive hot isostatic pressing high speed steels process. In a previous work a M3:2 high speed steel was vacuum sintered from irregular water atomized powders and had its sintering temperature determined. In this work the same powder was uniaxially cold compacted and vacuum sintered by adding some small quantity of graphite (0.3%C in weight) to prevent porosity and loss of carbon which result from the sintering cycle. The samples from all these experimental procedures were uniaxially cold compacted and vacuum sintered at five different temperatures and had its densities evaluated. The microstructure was evaluated using optical-electronic techniques in order to investigate the best range of sintering temperature. At least five parallel samples were tested to each condition of sintering.

Structure formation during activated sintering of high-speed steel

Features of structure formation during activated sintering of high-speed steel using a boron-containing additive as an activator are studied. It is shown that presence of an activating additive, its composition and content in the charge, determine features of structure formation compared with sintering without an additive. In the temperature range for solid-phase sintering the content of additive in the charge and the ratio of its components have little effect on the average carbide component size. As temperature increases and there is an increase in boron content in the charge sintering is accompanied by both some increase in austenite grain size and development of a significant difference in carbide grain size. The effect of nickel on size reduction of sintered steel structural components is established.

Nitrogen Sintering of High Speed Steel Processed by Starch Consolidation

Two different high-speed steel (HSS) powders, M2 and T15 compositions, were evaluated in water-based processing by starch consolidation (SC) and sintering in a nitrogen atmosphere using different sintering temperatures. Materials were produced based on slurry compositions with different solids loading, 60.7 vol% for T15 and 61.5 vol% for M2. Shaped specimens were then sintered to near full density. T15 bodies were under-sintered at 1225°C whereas at 1240-1260°C a clear over-sintering by the presence of large grains and an extensive network of big carbides was found. M2 specimens reached optimum sintering temperature at 1275°C whereas an under-sintering at 1270°C and an over-sintering at 1280°C were achieved. Different alloy compositions and a varied degree of oxidation of the material during the water processing were considered as factors causing the different sintering performance for the both steels. These factors together with carbide to carbonitride transformation were also concluded to be responsible to the altering of the sintering temperatures compared to theoretically predicted by using Thermo-Calc©.

Colloidal Compaction of Fine Metallic Powders under High-speed Centrifugal Force-Compaction and Sintering of High Speed Steel-

Fine (4μm) and coarse (30μm) water atomized high speed steel powders were prepared as slips and compacted by high-speed centrifugal compaction process (HCP).The HCP green compacts of the both fine and coarse powders can be sintered to almost full density at 1448K to 1498K without any pressure assistance during sintering. Their sintering behavior, however, were quite different. While the compact of coarse powder needed to form a liquid phase to densify and resulted in a coarse microstructure, that of fine powders densified in solid phase so that fine microstructures were obtained. A homogeneous packing of fine several micron powder by the HCP was essential to solid state sintering of high speed steel. The HCP compact of fine powders showed a comparable hardness and strength to wrought materials.

Microstructural Development and Mechanical Properties of High Speed Steels

A study was made of the sintering of high speed steel (HSS), M3/2, with different percentage additions - (0%, 2.5%, 5% and 8% by vol.) - of niobium carbide. The mixture was ground in a high speed ball mill to ensure smooth distribution and a material free from agglomerates. All the mixtures were sintered at temperatures above that of solidus, higher temperatures being required as the proportion of the niobium carbide was increased. The variation of the density and hardness were measured, as well as the evolution of the microstructure and the composition of the carbides with the sintering temperature.

Effect of nitrogen on supersolidus sintering of high speed steel

We have developed high performance silver sheathed Bi2223 wire. The progress in three years is especially remarkable. This dramatic development has been made with the controlled overpressure (CT-OP) sintering technique. The CT-OP sintering technique improves not only the critical current but also other performances such as n-value and mechanical strength, because of the improvement of the relative density up to almost 100%, the homogenization of the Bi2223 phase and the stronger connectivity between the Bi2223 grains. The dense Bi2223 wire prevents the ballooning phenomenon which is caused by the gasification of the trapped liquid nitrogen during warming up to room temperature.Present critical current has reached as about twice high as that in those days and shows over 200 A (77 K, self-field), which showed an excellent critical current property in a magnetic field.

Liquid phase sintering of high speed steels : A.S.Wronski et al. (University of Bradford, Bradford, UK.) Powder Metall., vol 42, no 2, 1999, 131–146

Liquid phase sintering of high speed steels : A.S.Wronski et al. (University of Bradford, Bradford, UK.) Powder Metall., vol 42, no 2, 1999, 131–146

Supersolidus liquid phase sintering of high speed steels: Part 3: computer aided design of sinterable alloys

Calculated multicomponent phase diagrams were used to identify high speed steel (HSS) type alloys having the potential to exhibit enhanced sinter ability. The requirement was for an extensive austenite + carbide + liquid phase field. Of the six tungsten and molybdenum based systems studied, Fe–14Mo–C + 4Cr–8Co systems were potentially the most promising. Appropriate compositions were water atomised and additional alloys prepared by blending annealed powders with graphite powders. Powders were compacted to green densities of about 70% theoretical and then vacuum sintered. Sinterability was assessed in terms of sintered densities and microstructures. Alloys containing Fe–13Mo–1·3C, Fe–14Mo–4Cr–1·3C, and Fe–14Mo– 8Co–4Cr–1·4C were sintered to full density at temperatures as low as 1170°C, 70–150 K lower than for existing HSSs. Sintering windows were 20– 30 K, a significant improvement on existing HSSs. As sintered microstructures consisted of angular M6 C carbides dispersed in martensitic matrixes, which is typical for correctly sintered HSS. Heat treatment response and cutting performance for the sinterable grades were assessed and found to be comparable to existing HSS. The cutting performance of Fe–14Mo– 8Co–4Cr–1·4C tools at 45 and 52·5 m min-1 was superior to both cast wrought M2 and T1 tools of identical geometry. Lower carbon contents resulted in an increase in sintering temperature and a reduction in the width of the sintering window. Higher carbon contents destroyed sinterability, since they led to the formation of M2 C eutectic structures in the undersintered condition. Alloy sinterability was correlated to differential thermal analysis data obtained during heating of powders. The variations in sinterability with alloy composition are discussed with reference to phase diagrams; the degradation in sinterability observed at carbon contents above 1·4% is attributed to the presence of ternary eutectic phase fields. The commercial implications of the relationship between sinterability and alloy composition are discussed.

Sintering of high speed steels under pressure of nitrogen: F.Castro et al. (CEIT, Spain.)

Sintering of high speed steels under pressure of nitrogen: F.Castro et al. (CEIT, Spain.)

Study of activated sintering of high speed steel by differential thermal analysis : S.N. Kaplya et al.Poroshkovaya Metallurgiya, no 1/2, 1995, 26–28. (In Russian.)

Nickel-based alloys can be machined using techniques similar to those employed to cut ferrous materials, however, additional requirements are imposed due to the poor machinability of these alloys. Through a series of cutting tests, the authors have applied techniques to optimise the cutting conditions for high speed steel circular saw blades machining materials from three principal categories of nickel-based alloy. The current paper considers the resultant wear mechanisms and the suitability of these tools for this application.Cutting tests were undertaken in which Cupro 107, Inconel 600L1 and Nimonic PK311 workpieces were machined over a range of cutting speeds and feeds to determine the optimum cutting conditions. Test results showed considerable variation in blade performance when cutting these materials. These variations were reflected in the rate of wear and the predominant wear mechanisms associated with the machining of each material.Since both tool and material costs are high, identification of the dominant wear mechanisms is of importance to both manufacturing engineer and end-user when assessing the suitability of using circular saw blades for this application, and when selecting the cutting conditions to maximise tool life. The work will also be of interest to the surface coating engineer when evaluating tooth geometry and substrate material requirements.

Sintering of high speed steel with copper phosphide and titanium based ceramic compounds : M.M. Oliveira, J.D. Bolton. (University of Bradford, Bradford, UK). Powder Metall., vol 38, no 2, 1995, 131–140

Nanocrystalline Ni2P was successfully prepared through the reaction between anhydrous NiCl2 and Na3P via the solvent–thermal method at 150°C. This method is similar to the well known hydrothermal process, except toluene is substituted for water. X-ray diffraction analysis indicated that the product was Ni2P phase, and no Ni–O vibrations were found in infrared spectra. Transmission electron microscopy showed that the average particle size was about 10 nm, and the particle-size distribution was narrow.

Supersolidus sintering of high speed steels — Computer aided design of alloys: C.S. Wright et al (University of Bradford, Bradford, UK)

Supersolidus sintering of high speed steels — Computer aided design of alloys: C.S. Wright et al (University of Bradford, Bradford, UK)

Size evolution of carbides during sintering of high speed steels : J.M. Chaix et al (Inst. National Polytechnique, Grenoble, France)

Size evolution of carbides during sintering of high speed steels : J.M. Chaix et al (Inst. National Polytechnique, Grenoble, France)

Liquid phase sintering of high speed steels with additions of particulate hard ceramics and solid lubricants: J.D. Bolton, A.J. Gant (University of Bradford, Bradford, UK)

Liquid phase sintering of high speed steels with additions of particulate hard ceramics and solid lubricants: J.D. Bolton, A.J. Gant (University of Bradford, Bradford, UK)

Avoiding Grain Growth during the Supersolidus Sintering of High Speed Steels

Avoiding Grain Growth during the Supersolidus Sintering of High Speed Steels

Supersolidus Sintering of High Speed Steels: Part 1: Sintering of Molybdenum Based Alloys

(1993). Supersolidus Sintering of High Speed Steels: Part 1: Sintering of Molybdenum Based Alloys. Powder Metallurgy: Vol. 36, No. 3, pp. 213-219.

Sintering of high speed steels (HSS) containing niobium: F.A. Filho et al (Inst Pesq. Energiticas e Nucleares, Brazil)

Sintering of high speed steels (HSS) containing niobium: F.A. Filho et al (Inst Pesq. Energiticas e Nucleares, Brazil)

Liquid Phase Sintering in High Speed Steels

Abstract Supersolidus sintering of high speed steels (HSS) can give densities in excess of 98% of full density and good properties. This paper appraises the available data — mostly about M-2 and T-15 HSS — concerning the evidence for the liquid phase, role of carbon and carbide formers such as V, Mo, W and Cr, and the effects of process variables such as particle size, green density, and sintering time and temperature. Then, a new hypothesis is presented about the mechanism of full density sintering in HSS.

Liquid phase sintering in high speed steels

Supersolidus sintering of high speed steels (HSS) can give densities in excess of 98% of full density and good properties. This paper appraises the available data — mostly about M-2 and T-15 HSS — concerning the evidence for the liquid phase, role of carbon and carbide formers such as V, Mo, W and Cr, and the effects of process variables such as particle size, green density, and sintering time and temperature. Then, a new hypothesis is presented about the mechanism of full density sintering in HSS.