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Structure of high speed steel (HSS) powders produced by impact centrifugal atomization (ICA)
POWER PRODUCTION PRODUCTION OF FINE NICKEL POWDERS BY SPRAY PYROLYSIS K. Nagashima et ai, (gyushi Univ, Japan), J. M ~ Research, Vol 5, No 12, 1990, 2828-2834. Fine Ni powders w e r e produced by spr~,-pyrolysis of aqueous solutions of Ni chloride and/or nitrate in a hydrogennitrogen atmosphere. Reaction ] temperatures in the range 700 to 900 o C resulted in formation of hollow particles with a rough surface. There was a gradual t r a n s i t i o n to solid, smooth surfaced particles over the range 900 to 1500°C and at 1600°C smooth spherical particles with at mean diameter of 0.6 pLm were formed.
PRODUCTION OF METAL POWDERS IN ELECTRIC ARC A.V. Suslov, E.L. Deizin, Poroshkovaya MstaUu~fiya, No 12, 1990, I-5, (In Russian). The e x p e r i m e n t a l p r o d u c t i o n of spherical Cu and Mo powders during m e l t i n g in a p u l s e d electric arc is described and the effects of process v a r i a b l e s w e r e i n v e s t i g a t e d . The dispersivity of the powders was found to be influenced by the arc current, the distance between the electrodes and other geometric parameters. Control of powder dispersion was shown to be possible. It was suggested t h a t a pinch effect was a dominant mechanism in droplet formation.
STRUCTURE OF HIGH SPEED STEEL ( H 8 8 ) POWDERS PRODUCED BY M A C T CENTRIFUGAL ATOMIZATION (ICA)
CLASSIFICATION OF POWDERS BY USE OF AN ELECTRIC FIELD V.I. Lashmanov et ai, Porvshkovaya Metallw~jiya, No 12, 1990, 10-14, (In Russian). The effect of an electric field, containing static and dynamic components, on the dispersion of powders was studied with the objective of sorting particles according to size. Mathematical equations were derived relating powder dispersion to process conditions.
52 MPR July/August 1991
M.V. Vlasov~ V.S. Sinelinikova, Poroshko-
va#a MetaUu~giya~ No 1, 1991, 59-64, (In Russian). The reduction of mixtures of finely divided Cr and Si oxides using carbon as the reducing agent has been investigated using X-my and chemical analyses. The formation of carbides and silicides during the process was noted and this was found to be highly temperature dependent.
FORMATION OF BORON N I T R m E BY CARBOTHERMAL REDUCTION T.S. Barnitslm~a et ai, Poroshkovaya Meta/tu~/ya~ No 12, 1990, 55-60, (In Russian). Dispersion formation of BN2 has been studied by X-ray diffraction, spectroscopic techniques and chemical analysis. Reactions between boron oxides, nitrogen and carbides were investigated. It was found that the formation of the B nitride took place at the contact zones between the oxide, nitrogen and carbide.
EFFECT OF MECHANICAL ACTIVATION OF Ni OXIDE ON SUBSEQUENT REDUCTION K. Saez et al, ~rroshkovaya Metallu~iya, No 1, 1991, 8-11, (In Russian). Ni oxide powder was mechanically activated and the effect of this on the reduction to metal was investigated. It was shown that a more dispersed and active oxide was produced and that the reduction temperatures were reduced. The particle sizes of the Ni powder were decreased from 30 to 40 tun to 7.5 ~m for the activated material. Improved s i n t e r a b i l i t y was reported. Residual porosity of 5 to 6% was attributed to the presence of Mg and Si impurities.
S.Y. Golub et al, P o r u s ~ y a MeSaUurgiya, No 12, 1990, 6-10, (In Russian). PRODUCTION AND PROPERTIES OF Flake shaped tool steel powders, made by ICA, were examined by X-ray diffraction. Cooling rates were estimated to be 10e to 10s °C/sec. Structural differences were noted between the powders and those produced by other methods in that a high c o n c e n t r a t i o n of phase a n d r e t a i n e d austenite (T) was found in the ICA powders. The amount of 7 was reduced by roll grinding and this was attributed to a stain induced martensitic transformation.
CA~BO-THERMIC REDUCTION OF FINELY POWDERED MIXTURES OF CHROMIUM AND SILICON O ~ E 8
PRODUCTION OF GAS-ATOMIZED POWDERS W. Graf et ai, (Krupp Pulvermetail, Essen, Gernmny), MetalL, Vol 45, No 4, 1991, 348354, (In German). The principles of gas atomization and of t h e d e s i g n of p l a n t a r e o u t l i n e d . Installations with capacities of 100, 300 and 3000 kg are described and atomizing costs are discussed. Examples are given of powders with 50% of the powder in the size range 50 to 100 pan.
PREPARATION OF ULTRAFINE Mo POWDER BY CHEMICAL VAPOUR DEPOSITION (CVD) I~H. Lee et ai, (Chungnam National Univ, Tae,}on, Korea), J. Korean Insa of Metals, Vol 29, No 1, 1991, 3-10, (In Korean). Ultrafine Mo powder was produced by gas phase reaction between MoCIo and H2 in the range 500 to 900°C. The pro0~s and the powder were characterized with respect to specific surface, particle shape, size and size distribution, and reaction rate. Increase in temperature and/or partial pressures of the reactants resulted in increased specific surface and reaction rate. T h e particles were 20 to 30 nm in size and were spherical. On start up the particles tended to agglomerate in chain form.
PRESBINO A N D $1NTERING
COMPOSITE IRON/MLICON NITRIDE POWDER T.N. Miller et al, Po~shkovaya Metallurgiya, No 1, 1991, 23-26, (In Russian). The p r o d u c t i o n of Fe-SisN4-FeCls powder is discussed. The powder was used to apply a coating to a substrate by a plasma jet technique. The structures and phase compositions of the powder and the coating were determined.
RELATIONSHIPS BETWEEN PROPERTIES AND PARTICLE INT]gRGROWTH DURING HOT PRESSING OF POWDERS BY. Dorofeev et ai, Poros/tkm~ya Meta/lurgiya, No 12, 1990, 18-21, (In Russian). The possibility of increasing the degree
PRODUCTION OF METAL POWDERS IN ELECTRIC ARC A.V. Suslov, E.L. Deizin, Poroshkovaya MstaUu~fiya, No 12, 1990, I-5, (In Russian). The e x p e r i m e n t a l p r o d u c t i o n of spherical Cu and Mo powders during m e l t i n g in a p u l s e d electric arc is described and the effects of process v a r i a b l e s w e r e i n v e s t i g a t e d . The dispersivity of the powders was found to be influenced by the arc current, the distance between the electrodes and other geometric parameters. Control of powder dispersion was shown to be possible. It was suggested t h a t a pinch effect was a dominant mechanism in droplet formation.
STRUCTURE OF HIGH SPEED STEEL ( H 8 8 ) POWDERS PRODUCED BY M A C T CENTRIFUGAL ATOMIZATION (ICA)
CLASSIFICATION OF POWDERS BY USE OF AN ELECTRIC FIELD V.I. Lashmanov et ai, Porvshkovaya Metallw~jiya, No 12, 1990, 10-14, (In Russian). The effect of an electric field, containing static and dynamic components, on the dispersion of powders was studied with the objective of sorting particles according to size. Mathematical equations were derived relating powder dispersion to process conditions.
52 MPR July/August 1991
M.V. Vlasov~ V.S. Sinelinikova, Poroshko-
va#a MetaUu~giya~ No 1, 1991, 59-64, (In Russian). The reduction of mixtures of finely divided Cr and Si oxides using carbon as the reducing agent has been investigated using X-my and chemical analyses. The formation of carbides and silicides during the process was noted and this was found to be highly temperature dependent.
FORMATION OF BORON N I T R m E BY CARBOTHERMAL REDUCTION T.S. Barnitslm~a et ai, Poroshkovaya Meta/tu~/ya~ No 12, 1990, 55-60, (In Russian). Dispersion formation of BN2 has been studied by X-ray diffraction, spectroscopic techniques and chemical analysis. Reactions between boron oxides, nitrogen and carbides were investigated. It was found that the formation of the B nitride took place at the contact zones between the oxide, nitrogen and carbide.
EFFECT OF MECHANICAL ACTIVATION OF Ni OXIDE ON SUBSEQUENT REDUCTION K. Saez et al, ~rroshkovaya Metallu~iya, No 1, 1991, 8-11, (In Russian). Ni oxide powder was mechanically activated and the effect of this on the reduction to metal was investigated. It was shown that a more dispersed and active oxide was produced and that the reduction temperatures were reduced. The particle sizes of the Ni powder were decreased from 30 to 40 tun to 7.5 ~m for the activated material. Improved s i n t e r a b i l i t y was reported. Residual porosity of 5 to 6% was attributed to the presence of Mg and Si impurities.
S.Y. Golub et al, P o r u s ~ y a MeSaUurgiya, No 12, 1990, 6-10, (In Russian). PRODUCTION AND PROPERTIES OF Flake shaped tool steel powders, made by ICA, were examined by X-ray diffraction. Cooling rates were estimated to be 10e to 10s °C/sec. Structural differences were noted between the powders and those produced by other methods in that a high c o n c e n t r a t i o n of phase a n d r e t a i n e d austenite (T) was found in the ICA powders. The amount of 7 was reduced by roll grinding and this was attributed to a stain induced martensitic transformation.
CA~BO-THERMIC REDUCTION OF FINELY POWDERED MIXTURES OF CHROMIUM AND SILICON O ~ E 8
PRODUCTION OF GAS-ATOMIZED POWDERS W. Graf et ai, (Krupp Pulvermetail, Essen, Gernmny), MetalL, Vol 45, No 4, 1991, 348354, (In German). The principles of gas atomization and of t h e d e s i g n of p l a n t a r e o u t l i n e d . Installations with capacities of 100, 300 and 3000 kg are described and atomizing costs are discussed. Examples are given of powders with 50% of the powder in the size range 50 to 100 pan.
PREPARATION OF ULTRAFINE Mo POWDER BY CHEMICAL VAPOUR DEPOSITION (CVD) I~H. Lee et ai, (Chungnam National Univ, Tae,}on, Korea), J. Korean Insa of Metals, Vol 29, No 1, 1991, 3-10, (In Korean). Ultrafine Mo powder was produced by gas phase reaction between MoCIo and H2 in the range 500 to 900°C. The pro0~s and the powder were characterized with respect to specific surface, particle shape, size and size distribution, and reaction rate. Increase in temperature and/or partial pressures of the reactants resulted in increased specific surface and reaction rate. T h e particles were 20 to 30 nm in size and were spherical. On start up the particles tended to agglomerate in chain form.
PRESBINO A N D $1NTERING
COMPOSITE IRON/MLICON NITRIDE POWDER T.N. Miller et al, Po~shkovaya Metallurgiya, No 1, 1991, 23-26, (In Russian). The p r o d u c t i o n of Fe-SisN4-FeCls powder is discussed. The powder was used to apply a coating to a substrate by a plasma jet technique. The structures and phase compositions of the powder and the coating were determined.
RELATIONSHIPS BETWEEN PROPERTIES AND PARTICLE INT]gRGROWTH DURING HOT PRESSING OF POWDERS BY. Dorofeev et ai, Poros/tkm~ya Meta/lurgiya, No 12, 1990, 18-21, (In Russian). The possibility of increasing the degree