Showing papers in "Powder Metallurgy in 1989"
TL;DR: Determination des constantes elastiques de fers frittees ayant une porosite comprise entre 3 and 30%, faits a partir de poudres atomisees ou reduites chimiquement.
Abstract: Determination des constantes elastiques de fers frittees ayant une porosite comprise entre 3 et 30%, faits a partir de poudres atomisees ou reduites chimiquement, frittees a 1000 ou a 1200 o C pendant des durees de 5, 15, 60 ou 240 mn
29 citations
TL;DR: In this paper, the Sintering Behaviour of T42 Water Atomized High Speed Steel Powder Under Vacuum and Industrial Atmospheres with Free Carbon Addition is described. But this paper is based on a different approach.
Abstract: (1989). Sintering Behaviour of T42 Water Atomised High Speed Steel Powder Under Vacuum and Industrial Atmospheres with Free Carbon Addition. Powder Metallurgy: Vol. 32, No. 4, pp. 291-299.
25 citations
TL;DR: In this paper, composites de metallurgie des poudres alliage d'aluminium-graphite naturel (0.14% en volume) were preparation.
Abstract: Preparation de composites de metallurgie des poudres alliage d'aluminium-graphite naturel (0,14% en volume) et examen de leur comportement au frittage, de leur durete, de leur resistivite electrique et de leur microstructure
24 citations
TL;DR: In this article, the tensile properties, fatigue S-N curves in rotating bend, and threshold stress intensities for fatigue crack growth of three Distaloy type materials were analyzed in the light of metallographic and fractographic studies.
Abstract: Data are presented for the tensile properties, fatigue S–N curves in rotating bend, and threshold stress intensities for fatigue crack growth of three Distaloy type materials. Distaloys SA, AB, and AE have been studied in the density range 6400–7200 kg m−3, in the as sintered and quenched and tempered conditions. Combinations of threshold stress intensities and fracture stress are similar to those observed for some conventionally wrought engineering steels. Results are interpreted in the light of metallographic and fractographic studies. PM/0494
23 citations
TL;DR: In this paper, an additional model based on mechanisms for generation of porosity during straining is proposed, which depends on whether the porosity is interconnected or disconnected, and the model is shown to have mixed success in explaining the observations.
Abstract: Experimental data for the variations of elastic properties with porosity of powder metallurgy materials are reviewed briefly. Analytical and finite element models based on linear elasticity theory are shown to have mixed success in explaining the observations. An additional model is proposed based on mechanisms for generation of porosity during straining. Details of the model depend on whether the porosity is interconnected or disconnected. PM/0488
23 citations
TL;DR: In this paper, three routes for increasing the strength of sintered steels are identified: strength can be increased by increasing the density of the material, either during the compaction process or during sintering: several possible approaches are suggested.
Abstract: Three routes for increasing the strengths of sintered steels are identified First, strength can be increased by increasing the density of the material, either during the compaction process or during sintering: several possible approaches are suggested Second, strength can be increased through alloying the metallic matrix: the reasons for the selection of alloying elements, and the methods of alloying are considered Third, the alloyed metallic matrix can be strengthened either by quench hardening and tempering, or by precipitation hardening heat treatments, but the response to heat treatment depends on the homogeneity of the matrix The extremely heterogeneous compositions and structures of steels made from elemental or master alloy mixes, partially prealloyed powders, or coated powders present a unique opportunity to engineer structures that have desired combinations of properties PM/0492
22 citations
TL;DR: In this paper, structural and property assessment of spray-deposition M2 high speed steel has been carried out and the response of the material to hardening treatment has also been studied.
Abstract: Microstructural and property assessments have been undertaken on spray deposited M2 high speed steel in the as deposited condition and after hot forging. The response of the material to hardening treatment has also been studied. The microstructure of the as deposited material showed a small grain size with a cellular carbide network. Subsequent hot forging produced a uniform dispersion of fine (0·5–2 μm) carbides. Austenitising the as deposited sample at 1200°C resulted in spheroidisation of the continuous grain boundary M6C carbide film. EDX analysis showed the resultant spheroidised particles to be predominantly vanadium rich MC. No significant differences were observed between the hardening response of M2 high speed steel produced conventionally and by spray deposition. The bend strength values of spray deposited M2 were isotropic and similar to those observed for powder metallurgy samples. PM/0487
18 citations
TL;DR: In this article, it was shown that densification during vacuum sintering of T1 type high speed steel powders is due to the presence of a liquid phase and that sinterability is influenced by the molybdenum content of the T1 powder.
Abstract: It is shown that densification during vacuum sintering of T1 type high speed steel powders is due to the presence of a liquid phase and that sinter-ability is influenced by the molybdenum content of the T1 powder, with 0·5 wt-% being essential for satisfactory sintering behaviour. The results of differential thermal analysis, sintering trials, and microstructural studies carried out on three batches of T1 powder containing <0·02, 0·26, and 0·51 wt-%Mo are discussed with reference to phase diagrams. Sintering behaviour and sintered microstructures can be correlated with phase diagram predictions. For sintering to full density to occur, the solidus temperature must be exceeded. Optimal sintering occurs within the austenite + carbide + liquid region. The amount of liquid is also important. Increasing the molybdenum content changes the position of the solidus, promoting sintering through the formation of a larger volume fraction of liquid at the sintering temperature. PM/0491
14 citations
TL;DR: In this article, Finishing processes in powder metallurgy are described. But they do not cover the entire process of finishing process in powdermetallurgy, and are not considered in this paper.
Abstract: (1989). Finishing Processes in Powder Metallurgy. Powder Metallurgy: Vol. 32, No. 4, pp. 277-284.
13 citations
TL;DR: The authors describe des essais effectues pour revetir les surfaces des particules d'une poudre de fer avec different metaux (base cuivre, plomb, nickel), presentation des caracteristiques mecaniques des compacts produits avec les poudres composites.
Abstract: Description des essais effectues pour revetir les surfaces des particules d'une poudre de fer avec differents metaux (base cuivre, plomb, nickel). Presentation des caracteristiques mecaniques des compacts produits avec les poudres composites
12 citations
TL;DR: In this article, the vacuum sintering characteristics of T1 type water atomized powders containing 99·5% theoretical density were investigated and typical micrographs were presented, concluding that densification is via liquid phase mechanisms and the involvement of carbon and molybdenum is discussed.
Abstract: The vacuum sintering characteristics of cold compacted T1 type water atomised powders containing 99·5% theoretical) was achieved after only 10 min at 1320°C. Microstructural developments during sintering were investigated and typical micrographs are presented. It can be concluded that densification is via liquid phase mechanisms and the involvement of carbon and molybdenum is discussed. PM/0477
Journal Article•
TL;DR: Procede de fabrication des aimants permanents de terre: preparation de lalliage; prebroyage; broyage, controle et ajustement de la composition; pressage; frittage et traitement thermique; usinage; revetement; aimantation as discussed by the authors.
Abstract: Procede de fabrication des aimants permanents de terre: preparation de l'alliage; prebroyage; broyage, controle et ajustement de la composition; pressage; frittage et traitement thermique; usinage; revetement; aimantation. Assurance qualite et applications des produits obtenus
TL;DR: In this paper, the sintering behavior of AISI 316L powders alloyed with 20%Cu has been studied as a function of various Sintering parameters.
Abstract: The sintering behaviour of AISI 316L powders alloyed with 20%Cu has been studied as a function of various sintering parameters. Copper additions are known to improve compressibility, sinterability, and dimensional control of the final component, as well as improving the corrosion resistance of the sintered material. Specimens have been sintered in an industrial furnace using various N2–H2 atmospheres and sintering times. Microstructural and structural examination of the specimens revealed that: (i) copper additions can reduce nitride precipitation during sintering, thus preventing sensitisation; (ii) copper diffusion into the austenitic particles is promoted by hydrogen rich (i.e. reducing) atmospheres; and (iii) the chosen copper addition of 20% is excessive. The results confirm that copper can have a beneficial effect on the sintering process and in improving the final properties of components; however, its content must be optimised to obtain a homogeneous sintered material. Atmosphere composit...
TL;DR: Anisotropic shrinkage and thermal expansion have been quantified for nickel and iron powder compacts during sintering at 1423 K following initial compaction at 200, 300, or 400 MPa as discussed by the authors.
Abstract: Anisotropic shrinkage and thermal expansion have been quantified for nickel and iron powder compacts during sintering at 1423 K following initial compaction at 200, 300, or 400 MPa. Shrinkage was greater in the radial direction of the cylindrical compacts than in the axial one. An anisotropy treatment is developed to describe the shrinkage in a quantitative manner. A similar approach to the thermal expansion results in quantitative relations that are specific to the individual powders. PM/0482
TL;DR: Analyses metallographiques de comprimes obtenus par compactage par explosion a partir de poudres de cuivre et de fer as mentioned in this paper, a.k.a.
Abstract: Analyses metallographiques de comprimes obtenus par compactage par explosion a partir de poudres de cuivre et de fer. Etude de la structure des points formes entre les particules
TL;DR: Les calculs d'equilibre de phases a multicomposants peuvent aider d'une maniere souple a la prevision de la structure des materiaux complexes obtenus par des techniques telles que la solidification rapide and la formation mecanique d'alliages as mentioned in this paper.
Abstract: Les calculs d'equilibre de phases a multicomposants peuvent aider d'une maniere souple a la prevision de la structure des materiaux complexes obtenus par des techniques telles que la solidification rapide et la formation mecanique d'alliages. On discute ici son application a l'etude de l'effet de l'addition d'alliages a Co−W−C, des aciers a outils, des phenomenes de tension superficielle et de mouillage et des revetements pour depot en phase vapeur
TL;DR: In this paper, a poudre optimale for le frittage sous gaz d'un acier rapide is proposed, based on stabilite dimensionnelle des pieces frittees, leur durete et leur resistance a la flexion.
Abstract: Developpement d'une poudre optimale pour le frittage sous gaz d'un acier rapide. Les resultats des essais de frittage sont discutes en termes de stabilite dimensionnelle des pieces frittees, de leur durete et de leur resistance a la flexion. L'usinabilite et la resistance a la fatigue de contact par roulement ont egalement ete etudiees
TL;DR: In this paper, a cylindrical powder pellet is sandwiched between two steel rods (input and output bar), aligned linearly, and the free end of the input bar is struck by a small projectile, propagating a low intensity, short duration, compressive stress pulse across the specimen to the free part of the output bar.
Abstract: A test is described in which a cylindrical powder pellet is sandwiched between two steel rods (input and output bar), aligned linearly. The free end of the input bar is struck by a small projectile, propagating a low intensity, short duration, compressive stress pulse across the specimen to the free end of the output bar. This pulse is then reflected, causing the pellet to be loaded in tension. The strain pulses in the two bars are used to determine the elastic Young's modulus in tension and compression and the tensile strength of the pellet. Details are given of the apparatus used and the theory for calculation of the specimen stress and strain. The results are found to compare well with both uniaxial tension and diametral ‘Brazilian’ tests. The method is believed to be applicable to a wide range of powder compacts and porous materials. PM/0503
TL;DR: Etude detaillee, comprenant une modelisation, du chauffage par induction d'une serie de formes d'ebauches applicable a la production de pieces de construction mecanique en acier faiblement allie as mentioned in this paper.
Abstract: Etude detaillee, comprenant une modelisation, du chauffage par induction d'une serie de formes d'ebauches applicable a la production de pieces de construction mecanique en acier faiblement allie
TL;DR: In this article, mesures de surface specifiques ont ete realisees par B.E.T. sur des poudres d'alliage d'aluminium AA2014 solidifiees rapidement, produites par atomisation a l'aide d'un gaz inerte
Abstract: Des mesures de surface specifiques ont ete realisees par B.E.T. sur des poudres d'alliage d'aluminium AA2014 solidifiees rapidement, produites par atomisation a l'aide d'un gaz inerte
Journal Article•
TL;DR: A partir d'exemples de nouvelles applications de produits en lamelles, on demontre leur importance technique and economique croissante as mentioned in this paper.
Abstract: A partir d'exemples de nouvelles applications de produits en lamelles, on demontre leur importance technique et economique croissante
TL;DR: Shrinkage of nickel and iron compacts has been measured continuously during isothermal sintering at 1423K under a stream of Ar-7 vol.-%H2.
Abstract: Shrinkage of nickel and iron compacts has been measured continuously during isothermal sintering at 1423K under a stream of Ar–7 vol.-%H2. The results have been analysed to determine the quantitative agreement with phenomenological relationships given in the literature, with respect to both anisotropic and isotropic behaviour. These treatments are compared with the conventional treatment given in the literature. It is concluded that: (1) continuous measurement is necessary to follow shrinkage behaviour adequately; (2) quantitative description of the shrinkage is possible through suitable combination of several equations, each of which is applicable to a particular range of sintering. PM/0483
TL;DR: In this paper, a simple Kozeny Carman model of capillary flow was used to describe the flow behavior of typical media for powder metallurgical processing of bronze powder and stainless steel fiber.
Abstract: Powder metallurgical processing of bronze powder and stainless steel fibre is widely employed to produce porous media that are used for separating particles from liquids or gases. The powders and fibres are of uniform diameter and, consequently, it is found that the flow behaviour of typical media can be described by a simple Kozeny Carman model of capillary flow. Hydraulic oil containing a suspension of standard test dust has been passed through flat sheets of media and correlations have been established between the particle size of dust retained during the test and a structural pore size parameter describing the sample. Using the capillary model, it is also shown how media having a specific separation performance can be designed for more demanding applications such as the processing of high performance thermoplastics and the treatment of aqueous nuclear waste. PM/0505
TL;DR: In this article, the authors suggest quelques lignes directrices for the elimination of un exces de matiere dans les pieces de metallurgie des poudres, utilisant l'analyse des contraintes for verifier si les pieces ont la resistance adequate.
Abstract: Suggestion de quelques lignes directrices pour l'elimination d'un exces de matiere dans les pieces de metallurgie des poudres, utilisant l'analyse des contraintes pour verifier si les pieces ont la resistance adequate. On inclut l'essai preliminaire de quelques materiaux pour aider a determiner les contraintes et l'attention est portee sur les poutres et les anneaux, largement utilises comme pieces d'essai standard dans l'industrie de metallurgie des poudres
TL;DR: In this paper, the equations for un ecoulement plastique plan, which peuvent etre utilisees pour des materiaux, ayant une dilatation nulle ou negligeable.
Abstract: Obtention des equations pour un ecoulement plastique plan qui peuvent etre utilisees pour des materiaux ayant une dilatation nulle ou negligeable