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double sinter route
PM
An investigation of pressure sintering (HIP) on t h e p r o p e r t i e s of c e m e n t e d carbides is described. A c o m p a r i s o n is made between the properties of conventionally sintered and pressure sintered materials. F R A C T U R E T O U G H N E S S O F TWOPHASE TUNGSTEN CARBIDE-COBALT CERMETS
K.S. Ravichandran (Wright Patterson Air Force Base, Ohio, USA), A c t a Metall, Mater., Vol 42, No 1, 1994, 143-150. The fracture toughness of WC-Co was discussed with regard to prediction from fracture mechanism relationships. Resistance to f r a c t u r e is a t t r i b u t e d to plastic deformation of the Co matrix. It is a s s u m e d t h a t deformation of Co between the WC particles a p p r o x i m a t e s to ideal plastic flow of a ductile layer between rigid platens and this was incorporated in the fracture toughness predictions. Reasonable agreement between predicted and m e a s u r e d values of fracture t o u g h n e s s is reported. I N V E S T I G A T I O N OF D I R E C T S I N T E R I N G FOR P R O D U C T I O N OF T15 HIGH SPEED STEEL
J M . Gallardo, E.J. H e r r e r a (E.T.S. de I n g e n i e r o s I n d u s t r i a l e s , Seville, S p a i n ) , Rev. de Metall., Vol 29, No 6, 1993, 362367. (In Spanish). A study of the process variables affecting the production of T15 HSS is described. Processing was cold compaction and direct sintering. Emphasis is p l a c e d o n compaction pressure, bulk lubrication with graphite and die wall lubrication with Zn stearate and green strength and density of compacts. E L E C T R O N M I C R O S C O P E S T U D Y OF STEEL BONDED CEMENTED CARBIDE
W. Qiang et al (Hua Zhong University of Science and Technology, Wuhuan, China), P M Technology, Vol 11, No 3, 1993, 202207. Transmission microscopy studies of TiC 50Nb Steel bonded c e m e n t e d carbides is described. Structure is shown to influence p r o p e r t i e s due to t h e p r e c i p i t a t i o n of carbides in the steel matrix.
Mechanical alloying M E C H A N I C A L ALLOYING OF IRONS I L I C O N P O W D E R S A N D E F F E C T S OF HEAT TREATMENT
S.Shiga et al (Nihama College of Technology, Nihama, J a p a n ) , J. J a p a n Soc. P o w d e r a n d P o w d e r M e t a l l u r g y , Vol 40, No 8, 1993, 770-773. (In J a p a n e s e ) . An investigation of MA of Si-(10 to 50) at%Fe is described. The MA powders were
LITERATURE
REVIEW
characterized. It is r e p o r t e d t h a t ~FeSi is formed in Si-50at%Fe and [3FeSi2 in Si30%Fe. Equilibrium p h a s e s were formed on heating in the range 900 to 1000°C and air cooled.
pM2TEC'94. The abstracts which follow are for papers which were presented at the international Conference on P o w d e r Metallurgy and Particulate Materials which was held in T o r o n t o , C a n a d a from 8th to l lth M a y 1994.
Powder production I M P R O V E M E N T S ON A T O M I Z E D POWDERS THROUGH ORIENTED P R O B L E M SOLVING
D.J. K a s p u t i s et al ( H o e g a n a e s Corp, Riverton, New Jersey, USA). The total quality of the system in use for p r o d u c t i o n of a t o m i z e d p o w d e r s w a s described. The i m p o r t a n c e of employee participation was emphasized. The p h a s e s of t h e o p e r a t i o n s , p r o d u c t c o n t r o l , statistics, documentation, personal development and process development w e r e c o n s i d e r e d . I m p r o v e m e n t in t h e microcleanliness of powders was used as an example. OXYGEN IN I R O N A N D S T E E L POWDERS
S.M. Kaufman (Peerless Metal Powders and Abrasives, USA). An investigation of the chemistry and stability of the oxides formed in Fe and steel powder during processing was described, it was r e p o r t e d t h a t additions of elements such as Si or A1 increased the stability of the oxides but t h a t the oxide of Si may be reduced in presence of enough C. Thermodynamics was used to justify the conclusion. MICROSTRUCTURAL DEVELOPMENT IN P O W D E R A T O M I Z A T I O N
W.J. Boettinger (NIST, USA). Microstructural evolution during atomization to powder was discussed with regard to nucleation, freezing rate and motion of the liquid/solid interface. An e x p e r i m e n t a l study of A1-8wt%Fe alloys was described in which distinct microstructures were observed according to particle sizes. In the finest powder, 10 prom, with a large d e g r e e of u n d e r c o o l i n g , a two z o n e structure of coarse and fine ~ cells was found. As particle size increased structures of ~kl and ~AI/FeAI3 with eutectic were formed. In particles above 40 p m m proeutectic FeAl~ was present.
Compaction DENSITY DISTRIBUTION AND MAGNETIC FLUX DURING C O M P A C T I O N IN M A G N E T I C F I E L D H. Kotera, S. Shima (Kyoto University, Kyoto, J a p a n ) . The compaction of magnetic materials in a m a g n e t i c field was reviewed w i t h r e s p e c t to p r o d u c t a n d p r o c e s s i m p r o v e m e n t s , m o v e m e n t s of p a r t i c l e s in the applied field, effects at the diewall a n d d e n s i t y d i s t r i b u t i o n s . F i n i t e element analysis was applied 1,o density distribution to determine tile relationships between powder/die-wall interactions, density and magnetic flux. Effects of m a g n e t i c flux on i n t e r n a l s t r e s s e s in c o m p a c t s d u r i n g c o n s o l i d a t i o n were discussed. N E W E X T R U S I O N M E T H O D FOR C O N S O L I D A T I O N OF P O W D E R S
H. Hoshino, S. Kohara (Science University of Tokyo, J a p a n ) . The use of extrusion for the c o n s o l i d a t i o n of metal p o w d e r s was discussed. It was noted t h a t there may be considerable residual porosity which has a d e t r i m e n t a l effect on properties. A m o d i f i e d e x t r u s i o n t e c h n i q u e , which was reported to result in lower porosity, by giving larger s h e a r deformation, was described. The p o w d e r was c o m p r e s s e d i n t o a c y l i n d e r and t h e n e x t r u d e d at r i g h t a n g l e s to t h e a x i s of t h e f i r s t c o m p r e s s i o n . It w a s r e p o r t e d t h a t densities of 98 to 99% were a t t a i n e d and a t e n s i l e s t r e n g t h of 120 MPa for AI deformed 30% in extrusion. N E T S H A P E F O R G I N G OF H I P IMPLANT COMPONENTS
R.V. Raman, S.V. Rele (Ceracon Inc, Scaramento, California, USA). The manufacture of femoral stems and h e a d s for hip p r o s t h e s e s was discussed with reference to forging. It was suggested that production from metal powder may offer a lower cost m e t h o d d e p e n d e n t on the attainment of satisfactory p r o p e r t i e s . An i n v e s t i g a t i o n , w h i c h considered net s h a p e forming, evaluation of m e c h a n i c a l p r o p e r t i e s a n d w e a r , was described. Dimensional control was analyzed. M A N U F A C T U R E OF H I G H P E R F O R M A N C E S I N T E R E D S T E E L S BY A DOUBLE PRESS/DOUBLE SINTER ROUTE
I.W. Donaldson, R.R. Biederman (The Presmet Corp, Worcester, USA). It was r e p o r t e d t h a t a double p r e s s / double sinter route had been used to p r o c e s s f e r r o u s m a t e r i a l s to h i g h d e n s i t y a n d high levels of m e c h a n i c a l
MPR N o v e m b e r 1994 39
properties. Results of a study of t h e e f f e c t s of p r o c e s s c o n d i t i o n s o n physical a n d mechanical properties were p r e s e n t e d a n d d i s c u s s e d for s t e e l s in the h e a t t r e a t e d or sinter h a r d e n e d states. NEW MATERIALS AND OPTIMIZED P R O C E S S E S FOR POWDER FORGED COMPONENTS
E. Eilrich, H. Neubert (Kresbsoge Sinterholding GmbH, Radevormwald, Germany). Powder forging of a u t o m o t i v e p a r t s w a s d i s c u s s e d w i t h c o n s i d e r a t i o n of t h e recent application to t h e p r o d u c t i o n of c o n n e c t i n g rods. It w a s c o n s i d e r e d that powder forging has significant technical a n d economic benefits arising from close d i m e n s i o n a l tolerances, weight reduction a n d e l i m i n a t i o n of machining. It was reported t h a t f u r t h e r i m p r o v e m e n t s m a y be possible in p r o p e r t i e s by h e a t t r e a t m e n t or new alloys.
Delubrication CASE HISTORIES OF DELUBRICATION PROBLEMS IN THE POWDER METALLURGY INDUSTRY
H.S. Nayar (BDC Group, USA). A study of the delubrication of PM c o m p a c t s was d e s c r i b e d . P r o b l e m s arising in t h e case studies, d e p o s i t i o n of soot, d i m e n s i o n a l c o n t r o l , p r o p e r t y changes and environmental emissions, were considered. Characteristics and p r o c e s s c o n d i t i o n s for e a c h p a r t were given. D a t a was analyzed to d e t e r m i n e common factors and variables in delubrication. E F F E C T S OF CHEMISTRY AND COMPACT DENSITY ON DECOMPOSITION OF PM LUBRICANTS
J.N. Aubon, J.S. Choo ( S h a m r o c k Technologies Inc, USA). The decomposition of olefins, b i s t e a r a m i d e s a n d m e t a l s t e a r a t e s was investigated with the objective of establishing relationships between c o m p a c t c h a r a c t e r i s t i c s a n d effects of l u b r i c a n t decomposition. DELUBRICATION OF PM IRONCOPPER-CARBON S T E E L S AND MODELLING
A. Griffo et al (Pennyslvania State University, Pennsylvania, USA). A study of delubrication of low, m e d i u m and high density Fe-2wt%Cu-0.8%C/ Acrawax compacts was described. Heating and cooling rates, dwell time and t e m p e r a t u r e were varied a n d p a r t s were c h a r a c t e r i z e d for d i m e n s i o n s , C a n d O c o n t e n t s a n d presence of soot. The d a t a d e t e r m i n e d was reported to allow more effective a n d efficient delubrication.
40 MPR November 1994
Sintering MODELLING OF PORE SIZE DISTRIBUTION AND E F F E C T ON LIQUID PHASE SINTERING
R.M. G e r m a n et al (Pennsylvania State University, Pennsylvania, USA). Use of c o m p u t e r simulation to model pore size distribution a n d to predict density was d e s c r i b e d for varying p o w d e r size mixtures. The simulations were c o m p a r e d with e x p e r i m e n t a l data. The predicted pore size d i s t r i b u t i o n s were u s e d to m o d e l densification in liquid p h a s e sintering by identifying t h e limiting factors. O p t i m u m p a c k i n g of p a r t i c l e s is p r e d i c t e d for i n t e n d e d microstructures. The implications were discussed. COMPUTER MODELLING AND D E S I G N OF SINTERING FURNACE ATMOSPHERES
T.Philips et al (Airco Bulk Gases, Murray Hill, New Jersey, USA). It was n o t e d t h a t a sintering process may require gases of different c o m p o s i t i o n in different p a r t s of t h e furnace in order to optimize metallurgical requirements. Fluid flow dynamics were modelled numerically with effects of variables incorporated. The c o m p u t e r s i m u l a t i o n s were used to design o p t i m u m s i n t e r i n g a t m o s p h e r e systems. C o m p a r i s o n s were m a d e w i t h e x i s t i n g industrial systems. SCIENTIFIC PRINCIPLES OF HIGH TEMPERATURE SINTERING OF FERROUS MATERIALS
m a d e between low-alloy steels sintered at high a n d conventional t e m p e r a t u r e s a n d m a d e from mixed, partially alloyed a n d prea l l o y e d p o w d e r s . E f f e c t of s i n t e r i n g t e m p e r a t u r e on s t r u c t u r e a n d p r o p e r t i e s were reviewed. D E S I G N I S S U E S IN HIGH T E M P E R A T U R E S I N T E R E D PARTS
H.I. S a n d e r o w ( M a n a g e m e n t a n d Engineering Technologies Inc, Dayton, Ohio, USA). Design issues arising from t h e use of h i g h t e m p e r a t u r e s for s i n t e r i n g w e r e discussed a n d t h e need for t h e designer to u n d e r s t a n d high t e m p e r a t u r e sintering a n d it's effects was e m p h a s i z e d t o g e t h e r with t h e i m p o r t a n c e of good process a n d quality control. It was n o t e d t h a t some form of sizing o p e r a t i o n m a y be needed in p a r t s which s i n t e r to full density. Some p r o b l e m s a n d t h e need to modify process e q u i p m e n t were noted. HIGH T E M P E R A T U R E SINTERING OF STAINLESS S T E E L S AND SOFT MAGNETIC MATERIALS
C. Lall (Midwest Sintered Products Corp, Riverdale, Illinois, USA). Effects of high t e m p e r a t u r e sintering on stainless steels a n d a range of soft m a g n e t i c alloys were described. High t e m p e r a t u r e s i n t e r i n g was s h o w n to m i n i m i z e t h e a b s o r p t i o n of N a n d p r e c i p i t a t i o n of nitrides on cooling a n d to p r o m o t e t h e reduction of oxides which i n h i b i t b o n d i n g of particles. A study of sintering 316L steel and magnetic alloys was described. Properties were correlated with C, N a n d O c o n t e n t s of t h e s i n t e r e d alloys. O p t i m u m process c o n d i t i o n s were d e t e r m i n e d for maximum density and minimum contamination.
R.M. G e r m a n et al (Pennsylvania S t a t e University, Pennsylvania, USA). The scientific principles underlying t h e use of high t e m p e r a t u r e sintering for steels were reviewed. Consideration was given to changes in sintering m e c h a n i s m s arising from t h e increase in t e m p e r a t u r e . It was e m p h a s i z e d t h a t a good u n d e r s t a n d i n g of t h e process is essential to avoid sintering at too high a t e m p e r a t u r e or for too long a time, w i t h c o n s e q u e n t d e g r a d a t i o n in properties. Analysis of t h e r e s p o n s e of steel to sintering at progressively i n c r e a s i n g t e m p e r a t u r e s was p r e s e n t e d w i t h d u e r e g a r d to p r o p e r t i e s . It was shown t h a t i m p r o v e m e n t s in p r o p e r t i e s can be achieved w h e n p r o p e r a t t e n t i o n is given to selection a n d control of p o w d e r characteristics a n d process conditions.
J. Szymorski, J. P r e g o w s k i ( R o t a p r e s s I n t e r n a t i o n a l Inc, C a n a d a ) , The h a r d w a r e for process m o n i t o r i n g a n d control of a rotary cold repressing system, used for sintering preforms, was described. The system was r e p o r t e d to a l l o w c o n t r o l of a n y p a r t of t h e process a n d to enable optimization to be carried out.
HIGH TEMPERATURE SINTERING OF LOW-ALLOY F E R R O U S MATERIALS
GEAR MANUFACTURE USING ROTARY REPRESSING
W.B. J a m e s (Hoeganaes Corp Inc, Riverton, New Jersey, USA). S t r u c t u r e / p r o p e r t y r e l a t i o n s h i p s in sintered steels were discussed with respect to powder properties, alloy composition a n d process conditions. A comparison was
J. Szymborski, J. Pregowski ( R o t a p r e s s I n t e r n a t i o n a l Inc, C a n a d a ) . Rotary repressing was r e p o r t e d to be a n effective m e a n s of fabricating near-nets h a p e c o m p o n e n t s w i t h h i g h densities. The use of t h e t e c h n i q u e for m a n u f a c t u r e
Post sintering operations QUALITY CONTROL THROUGH P R O C E S S MONITORING OF ROTARY FORMING P R E S S
An investigation of pressure sintering (HIP) on t h e p r o p e r t i e s of c e m e n t e d carbides is described. A c o m p a r i s o n is made between the properties of conventionally sintered and pressure sintered materials. F R A C T U R E T O U G H N E S S O F TWOPHASE TUNGSTEN CARBIDE-COBALT CERMETS
K.S. Ravichandran (Wright Patterson Air Force Base, Ohio, USA), A c t a Metall, Mater., Vol 42, No 1, 1994, 143-150. The fracture toughness of WC-Co was discussed with regard to prediction from fracture mechanism relationships. Resistance to f r a c t u r e is a t t r i b u t e d to plastic deformation of the Co matrix. It is a s s u m e d t h a t deformation of Co between the WC particles a p p r o x i m a t e s to ideal plastic flow of a ductile layer between rigid platens and this was incorporated in the fracture toughness predictions. Reasonable agreement between predicted and m e a s u r e d values of fracture t o u g h n e s s is reported. I N V E S T I G A T I O N OF D I R E C T S I N T E R I N G FOR P R O D U C T I O N OF T15 HIGH SPEED STEEL
J M . Gallardo, E.J. H e r r e r a (E.T.S. de I n g e n i e r o s I n d u s t r i a l e s , Seville, S p a i n ) , Rev. de Metall., Vol 29, No 6, 1993, 362367. (In Spanish). A study of the process variables affecting the production of T15 HSS is described. Processing was cold compaction and direct sintering. Emphasis is p l a c e d o n compaction pressure, bulk lubrication with graphite and die wall lubrication with Zn stearate and green strength and density of compacts. E L E C T R O N M I C R O S C O P E S T U D Y OF STEEL BONDED CEMENTED CARBIDE
W. Qiang et al (Hua Zhong University of Science and Technology, Wuhuan, China), P M Technology, Vol 11, No 3, 1993, 202207. Transmission microscopy studies of TiC 50Nb Steel bonded c e m e n t e d carbides is described. Structure is shown to influence p r o p e r t i e s due to t h e p r e c i p i t a t i o n of carbides in the steel matrix.
Mechanical alloying M E C H A N I C A L ALLOYING OF IRONS I L I C O N P O W D E R S A N D E F F E C T S OF HEAT TREATMENT
S.Shiga et al (Nihama College of Technology, Nihama, J a p a n ) , J. J a p a n Soc. P o w d e r a n d P o w d e r M e t a l l u r g y , Vol 40, No 8, 1993, 770-773. (In J a p a n e s e ) . An investigation of MA of Si-(10 to 50) at%Fe is described. The MA powders were
LITERATURE
REVIEW
characterized. It is r e p o r t e d t h a t ~FeSi is formed in Si-50at%Fe and [3FeSi2 in Si30%Fe. Equilibrium p h a s e s were formed on heating in the range 900 to 1000°C and air cooled.
pM2TEC'94. The abstracts which follow are for papers which were presented at the international Conference on P o w d e r Metallurgy and Particulate Materials which was held in T o r o n t o , C a n a d a from 8th to l lth M a y 1994.
Powder production I M P R O V E M E N T S ON A T O M I Z E D POWDERS THROUGH ORIENTED P R O B L E M SOLVING
D.J. K a s p u t i s et al ( H o e g a n a e s Corp, Riverton, New Jersey, USA). The total quality of the system in use for p r o d u c t i o n of a t o m i z e d p o w d e r s w a s described. The i m p o r t a n c e of employee participation was emphasized. The p h a s e s of t h e o p e r a t i o n s , p r o d u c t c o n t r o l , statistics, documentation, personal development and process development w e r e c o n s i d e r e d . I m p r o v e m e n t in t h e microcleanliness of powders was used as an example. OXYGEN IN I R O N A N D S T E E L POWDERS
S.M. Kaufman (Peerless Metal Powders and Abrasives, USA). An investigation of the chemistry and stability of the oxides formed in Fe and steel powder during processing was described, it was r e p o r t e d t h a t additions of elements such as Si or A1 increased the stability of the oxides but t h a t the oxide of Si may be reduced in presence of enough C. Thermodynamics was used to justify the conclusion. MICROSTRUCTURAL DEVELOPMENT IN P O W D E R A T O M I Z A T I O N
W.J. Boettinger (NIST, USA). Microstructural evolution during atomization to powder was discussed with regard to nucleation, freezing rate and motion of the liquid/solid interface. An e x p e r i m e n t a l study of A1-8wt%Fe alloys was described in which distinct microstructures were observed according to particle sizes. In the finest powder, 10 prom, with a large d e g r e e of u n d e r c o o l i n g , a two z o n e structure of coarse and fine ~ cells was found. As particle size increased structures of ~kl and ~AI/FeAI3 with eutectic were formed. In particles above 40 p m m proeutectic FeAl~ was present.
Compaction DENSITY DISTRIBUTION AND MAGNETIC FLUX DURING C O M P A C T I O N IN M A G N E T I C F I E L D H. Kotera, S. Shima (Kyoto University, Kyoto, J a p a n ) . The compaction of magnetic materials in a m a g n e t i c field was reviewed w i t h r e s p e c t to p r o d u c t a n d p r o c e s s i m p r o v e m e n t s , m o v e m e n t s of p a r t i c l e s in the applied field, effects at the diewall a n d d e n s i t y d i s t r i b u t i o n s . F i n i t e element analysis was applied 1,o density distribution to determine tile relationships between powder/die-wall interactions, density and magnetic flux. Effects of m a g n e t i c flux on i n t e r n a l s t r e s s e s in c o m p a c t s d u r i n g c o n s o l i d a t i o n were discussed. N E W E X T R U S I O N M E T H O D FOR C O N S O L I D A T I O N OF P O W D E R S
H. Hoshino, S. Kohara (Science University of Tokyo, J a p a n ) . The use of extrusion for the c o n s o l i d a t i o n of metal p o w d e r s was discussed. It was noted t h a t there may be considerable residual porosity which has a d e t r i m e n t a l effect on properties. A m o d i f i e d e x t r u s i o n t e c h n i q u e , which was reported to result in lower porosity, by giving larger s h e a r deformation, was described. The p o w d e r was c o m p r e s s e d i n t o a c y l i n d e r and t h e n e x t r u d e d at r i g h t a n g l e s to t h e a x i s of t h e f i r s t c o m p r e s s i o n . It w a s r e p o r t e d t h a t densities of 98 to 99% were a t t a i n e d and a t e n s i l e s t r e n g t h of 120 MPa for AI deformed 30% in extrusion. N E T S H A P E F O R G I N G OF H I P IMPLANT COMPONENTS
R.V. Raman, S.V. Rele (Ceracon Inc, Scaramento, California, USA). The manufacture of femoral stems and h e a d s for hip p r o s t h e s e s was discussed with reference to forging. It was suggested that production from metal powder may offer a lower cost m e t h o d d e p e n d e n t on the attainment of satisfactory p r o p e r t i e s . An i n v e s t i g a t i o n , w h i c h considered net s h a p e forming, evaluation of m e c h a n i c a l p r o p e r t i e s a n d w e a r , was described. Dimensional control was analyzed. M A N U F A C T U R E OF H I G H P E R F O R M A N C E S I N T E R E D S T E E L S BY A DOUBLE PRESS/DOUBLE SINTER ROUTE
I.W. Donaldson, R.R. Biederman (The Presmet Corp, Worcester, USA). It was r e p o r t e d t h a t a double p r e s s / double sinter route had been used to p r o c e s s f e r r o u s m a t e r i a l s to h i g h d e n s i t y a n d high levels of m e c h a n i c a l
MPR N o v e m b e r 1994 39
properties. Results of a study of t h e e f f e c t s of p r o c e s s c o n d i t i o n s o n physical a n d mechanical properties were p r e s e n t e d a n d d i s c u s s e d for s t e e l s in the h e a t t r e a t e d or sinter h a r d e n e d states. NEW MATERIALS AND OPTIMIZED P R O C E S S E S FOR POWDER FORGED COMPONENTS
E. Eilrich, H. Neubert (Kresbsoge Sinterholding GmbH, Radevormwald, Germany). Powder forging of a u t o m o t i v e p a r t s w a s d i s c u s s e d w i t h c o n s i d e r a t i o n of t h e recent application to t h e p r o d u c t i o n of c o n n e c t i n g rods. It w a s c o n s i d e r e d that powder forging has significant technical a n d economic benefits arising from close d i m e n s i o n a l tolerances, weight reduction a n d e l i m i n a t i o n of machining. It was reported t h a t f u r t h e r i m p r o v e m e n t s m a y be possible in p r o p e r t i e s by h e a t t r e a t m e n t or new alloys.
Delubrication CASE HISTORIES OF DELUBRICATION PROBLEMS IN THE POWDER METALLURGY INDUSTRY
H.S. Nayar (BDC Group, USA). A study of the delubrication of PM c o m p a c t s was d e s c r i b e d . P r o b l e m s arising in t h e case studies, d e p o s i t i o n of soot, d i m e n s i o n a l c o n t r o l , p r o p e r t y changes and environmental emissions, were considered. Characteristics and p r o c e s s c o n d i t i o n s for e a c h p a r t were given. D a t a was analyzed to d e t e r m i n e common factors and variables in delubrication. E F F E C T S OF CHEMISTRY AND COMPACT DENSITY ON DECOMPOSITION OF PM LUBRICANTS
J.N. Aubon, J.S. Choo ( S h a m r o c k Technologies Inc, USA). The decomposition of olefins, b i s t e a r a m i d e s a n d m e t a l s t e a r a t e s was investigated with the objective of establishing relationships between c o m p a c t c h a r a c t e r i s t i c s a n d effects of l u b r i c a n t decomposition. DELUBRICATION OF PM IRONCOPPER-CARBON S T E E L S AND MODELLING
A. Griffo et al (Pennyslvania State University, Pennsylvania, USA). A study of delubrication of low, m e d i u m and high density Fe-2wt%Cu-0.8%C/ Acrawax compacts was described. Heating and cooling rates, dwell time and t e m p e r a t u r e were varied a n d p a r t s were c h a r a c t e r i z e d for d i m e n s i o n s , C a n d O c o n t e n t s a n d presence of soot. The d a t a d e t e r m i n e d was reported to allow more effective a n d efficient delubrication.
40 MPR November 1994
Sintering MODELLING OF PORE SIZE DISTRIBUTION AND E F F E C T ON LIQUID PHASE SINTERING
R.M. G e r m a n et al (Pennsylvania State University, Pennsylvania, USA). Use of c o m p u t e r simulation to model pore size distribution a n d to predict density was d e s c r i b e d for varying p o w d e r size mixtures. The simulations were c o m p a r e d with e x p e r i m e n t a l data. The predicted pore size d i s t r i b u t i o n s were u s e d to m o d e l densification in liquid p h a s e sintering by identifying t h e limiting factors. O p t i m u m p a c k i n g of p a r t i c l e s is p r e d i c t e d for i n t e n d e d microstructures. The implications were discussed. COMPUTER MODELLING AND D E S I G N OF SINTERING FURNACE ATMOSPHERES
T.Philips et al (Airco Bulk Gases, Murray Hill, New Jersey, USA). It was n o t e d t h a t a sintering process may require gases of different c o m p o s i t i o n in different p a r t s of t h e furnace in order to optimize metallurgical requirements. Fluid flow dynamics were modelled numerically with effects of variables incorporated. The c o m p u t e r s i m u l a t i o n s were used to design o p t i m u m s i n t e r i n g a t m o s p h e r e systems. C o m p a r i s o n s were m a d e w i t h e x i s t i n g industrial systems. SCIENTIFIC PRINCIPLES OF HIGH TEMPERATURE SINTERING OF FERROUS MATERIALS
m a d e between low-alloy steels sintered at high a n d conventional t e m p e r a t u r e s a n d m a d e from mixed, partially alloyed a n d prea l l o y e d p o w d e r s . E f f e c t of s i n t e r i n g t e m p e r a t u r e on s t r u c t u r e a n d p r o p e r t i e s were reviewed. D E S I G N I S S U E S IN HIGH T E M P E R A T U R E S I N T E R E D PARTS
H.I. S a n d e r o w ( M a n a g e m e n t a n d Engineering Technologies Inc, Dayton, Ohio, USA). Design issues arising from t h e use of h i g h t e m p e r a t u r e s for s i n t e r i n g w e r e discussed a n d t h e need for t h e designer to u n d e r s t a n d high t e m p e r a t u r e sintering a n d it's effects was e m p h a s i z e d t o g e t h e r with t h e i m p o r t a n c e of good process a n d quality control. It was n o t e d t h a t some form of sizing o p e r a t i o n m a y be needed in p a r t s which s i n t e r to full density. Some p r o b l e m s a n d t h e need to modify process e q u i p m e n t were noted. HIGH T E M P E R A T U R E SINTERING OF STAINLESS S T E E L S AND SOFT MAGNETIC MATERIALS
C. Lall (Midwest Sintered Products Corp, Riverdale, Illinois, USA). Effects of high t e m p e r a t u r e sintering on stainless steels a n d a range of soft m a g n e t i c alloys were described. High t e m p e r a t u r e s i n t e r i n g was s h o w n to m i n i m i z e t h e a b s o r p t i o n of N a n d p r e c i p i t a t i o n of nitrides on cooling a n d to p r o m o t e t h e reduction of oxides which i n h i b i t b o n d i n g of particles. A study of sintering 316L steel and magnetic alloys was described. Properties were correlated with C, N a n d O c o n t e n t s of t h e s i n t e r e d alloys. O p t i m u m process c o n d i t i o n s were d e t e r m i n e d for maximum density and minimum contamination.
R.M. G e r m a n et al (Pennsylvania S t a t e University, Pennsylvania, USA). The scientific principles underlying t h e use of high t e m p e r a t u r e sintering for steels were reviewed. Consideration was given to changes in sintering m e c h a n i s m s arising from t h e increase in t e m p e r a t u r e . It was e m p h a s i z e d t h a t a good u n d e r s t a n d i n g of t h e process is essential to avoid sintering at too high a t e m p e r a t u r e or for too long a time, w i t h c o n s e q u e n t d e g r a d a t i o n in properties. Analysis of t h e r e s p o n s e of steel to sintering at progressively i n c r e a s i n g t e m p e r a t u r e s was p r e s e n t e d w i t h d u e r e g a r d to p r o p e r t i e s . It was shown t h a t i m p r o v e m e n t s in p r o p e r t i e s can be achieved w h e n p r o p e r a t t e n t i o n is given to selection a n d control of p o w d e r characteristics a n d process conditions.
J. Szymorski, J. P r e g o w s k i ( R o t a p r e s s I n t e r n a t i o n a l Inc, C a n a d a ) , The h a r d w a r e for process m o n i t o r i n g a n d control of a rotary cold repressing system, used for sintering preforms, was described. The system was r e p o r t e d to a l l o w c o n t r o l of a n y p a r t of t h e process a n d to enable optimization to be carried out.
HIGH TEMPERATURE SINTERING OF LOW-ALLOY F E R R O U S MATERIALS
GEAR MANUFACTURE USING ROTARY REPRESSING
W.B. J a m e s (Hoeganaes Corp Inc, Riverton, New Jersey, USA). S t r u c t u r e / p r o p e r t y r e l a t i o n s h i p s in sintered steels were discussed with respect to powder properties, alloy composition a n d process conditions. A comparison was
J. Szymborski, J. Pregowski ( R o t a p r e s s I n t e r n a t i o n a l Inc, C a n a d a ) . Rotary repressing was r e p o r t e d to be a n effective m e a n s of fabricating near-nets h a p e c o m p o n e n t s w i t h h i g h densities. The use of t h e t e c h n i q u e for m a n u f a c t u r e
Post sintering operations QUALITY CONTROL THROUGH P R O C E S S MONITORING OF ROTARY FORMING P R E S S