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A review of numerical and computational techniques in powder metallurgy
PM
An invesligation o1' lhe eflk~cts of h e a t t r e a t m e n t on tim cutting p r o p e r t i e s of WCTiC-TaC Co alloys w a s described. It was reported that repeated thermal shock resulted in decline in s t r e n g t h a n d t h a t t h i s could be p r e v e n t e d by heat t r e a t m e n t . This was atl ributed lo transtkwmation of t h e Co hinder p h a s e from a h e x a g o n a l to a cubic s t r u c t u r e d u r i n g heal t r e a t m e n l a n d the binder was t h e n over s a t u r a t e d }~4th sohlle species. The results of c u t t i n g t e s t s were shown to be in a g r e e m e n t with t h e t h e r m a l shock t c s l s a n d it was d e d u c e d t h a t the h e a t t r e a t m e n t is beneficial in e n h a n c i n g c u t t i n g performance.
E N G I N E E R I N G APPLICATIONS OF DIFFUSION BONDING BRAZING AND HARD FACING FOR HIGH PERFORMANCE TOOLS AND DIES .I.M. l'anchal, T. Vela (Alloy Technology Int lnc, New York, IJSA). The ability of Ferro TiC c o m p o s i t e s to t i n d e r go m a c h i n i n g , h e a t t r e a t m e n t , welding, brazing a n d diffusion b o n d i n g as overlays on tools and dies was d i s c u s s e d w i t h r e s p e c t 1o ( , n h a n ( ' e n / e n l of w e a r properties. The rang(' <)f TiC m a t e r i a l s bonded with steel, tool steel, allot sleel or hard m a t r i x m a t e r i a l s was outlined a n d it was noted lha[ the m a t e r i a l s are being u s e d in aggressive set~.i<-e conditions. Processes a n d a p p l i c a t i o n s were discussed.
T U N G S T E N AND T U N G S T E N BASED COMPOSITES AND ALLOYS FOR HIGH HEAT FLUX DUTY tt.L. Marcus el al (liniversily of Texas, Austin, Texas, USA). An i n v e s t i g a t i o n ~)1 t h e i n f l u e n c e of n/icrostrncttlle o11 n/ass loss fronl ~'-(~11 a n d W Mo alloys u n d e r high heat flux w a s described. The s p e c i n n m s were p r e p a r e d f r o m a l h ) y p o w d e r s , m a d e by r a p i d r e d u c t i o n of ulIral'il/e (helow 200 n m ) oxide powders by cor,ventional p r e s s - a n d s m t e r and high ener~5' r a w m e l h o d s . The h a r d n e s s e s were reported to be higher t h a n commercially available alloys anti t h i s was a t t r i b u t e d to high connectivity a n d Hall l'etch hardening. The results of characterization of heal scarred s u r f a c e s a n d ejected m a t t e r were i n c o r p o r a t e d into a crevice evaporation model. The s t r u c t u r e of l h e W skeleton w a s said lo d e l e r m i n e w h e t h e r
MOLYBDENUM-HAFNIUM-CARBON ALLOYS FOR ELEVATED TEMPERATURE APPLICATIONS R. Daga (Metadyne lnc, USA). The manufacture of p r e c i p i t a t i o n h a r d e n i n g Mo-Hf-C alloys w a s r e p o r t e d and process methods described. The s i n t c r e d billets were l h e r m o m e c h a n i c a l l y p r o c e s s e d into rod a n d wire. C o m p o s i t i o n
LITERATURE
REVIEW
microstructural homogeneity, aging r e s p o n s e a n d m e c h a n i c a l p r o p e r t i e s were evaluated. It was r e p o r t e d t h a t t h e alloys h a d s u p e r i o r elevated t e m p e r a t u r e s t r e n g t h to commercially available Mo alloys.
FABRICATION AND HIGH TEMPERATURE BRAZING OF MOLYBDENUM-RHENIUM ALLOYS J.A. Shiehts et al ( C l i m a x Speciality Metals, Cleveland, Ohio, USA). T h e m a n u f a c t u r e of a n a e r o s p a c e c o m p o n e n t by m a c h i n i n g from a s i n t e r e d Mo alloy plate a n d a s i n t e r e d Mo-Re alloy t u b e a n d a Mo manifold, which were brazed together, at 700 C, w a s described. T h e c o m p o n e n t w a s i n t e n d e d to w i t h s t a n d severe vibration and thermal and m e c h a n i c a l s h o c k in a m a n n e d s p a c e vehicle. Production and testing were discussed.
Modelling and computational methods A REVIEW OF NUMERICAL AND COMPUTATIONAL T E C H N I Q U E S IN POWDER METALLURGY R.M. G e r m a n (t'ennsTlvania State University, Pennsylvania, USA). The use of n u m e r i c a l a n d c o m p u t a t i o n a l m e t h o d s for t h e m o d e l l i n g of PM u n i t p r o c e s s e s a n d o p e r a t i o n s w a s critically reviewed with reference to a t o m i z a t i o n , c o m p a c t i o n , sintering, injection m o u l d i n g , HIP a n d powder forging, The a p p l i c a t i o n s of c o m p u t e r s to p a r t design p r o c e s s control, d a t a collection a n d image analysis were discussed. The range of a p p l i c a t i o n from pairing of a t o m s to entire m a n u f a c t u r i n g sites were outlined with m e n t i o n of finite element analysis, statistics, modelling, management and knowledge based sTstems being c o n s i d e r e d in t h e light of t h e state-of-the-art.
EXPERIMENTAL D E S I G N AND RELATED STATISTICAL M E T H O D S IN E X P E D I T I N G TECHNICAL SOLUTIONS IN PARTICULATE TECHNOLOGY C.I. W']fitman (SSI M a n a g e m e n t Consult a n t s Inc, USA). Technical c h a l l e n g e s a n d s o l u t i o n s in particulate technology, ranging from trouble s h o o t i n g to d e v e l o p m e n t of new p r o c e s s e s a n d p r o d u c t s were 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 given to e x p e r i m e n t a l design, s t a t i s t i c a l m o d e l l i n g a n d p r o p e r t i e s of m a t e r i a l s . T h e v a l u e of t h e p e r s o n a l c o m p u t e r in p o w d e r m e t a l l u r g y w a s e m p h a s i s e d w i t h r e s p e c t to t h e available software.
APPLICATION OF COMPUTER A I D E D D E S I G N AND MANUFACTURING IN THE PM PARTS INDUSTRY B.A. Stebick (Windfall P r o d u c t s Inc, St Mary's, Penns?dvania, USA).
A c a s e s t u d y , w h i c h w a s s a i d to e m p h a s i s e t h e value of CAI)/CAM in t h e d e v e l o p m e n t , design a n d m a n u f a c t u r e of a PM c o m p o n e n t was p r e s e n t e d . It w a s noted t h a t CAD/CAM h a s h a d a significant effect on all a s p e c t s of PM fabrication.
MODELLING OF TItE POWDER METALLURGY P R O C E S S A. Lawley, B.L. F e r g u s o n ( l ) e f l ) r m a t i o n Control Technology Inc, USA). A critical a p p r a i s a l of m o d e l s of a wide range o f PM u n i t p r o c e s s e s and m e c h a n i s m s w a s presented. E m p h a s i s w a s p l a c e d on t h e i m p o r t a n c e of a c c u r a t e p r o c e s s d e s c r i p t i o n to o p t i m i s e t h e m a n u f a c t u r i n g cycle with t h e objective of u s i n g real t i m e p r o c e s s control.
INTEGRATED COMPUTER A I D E D D E S I G N AND ANALYSIS OF POWDER METALLURGY PRODUCTS M. Guillot et al (Laval Uniwxsity, C a n a d a ) . An i n t e g r a t e d c o m p u t e r aided e l e m e n t m e t h o d a p p r o a c h for design a n d analysis of PM p a r t s was presented. Density d i s t r i b u t i o n s , die filling time, (:racking d u r i n g c o m p a c t i o n a n d ejection, p r o p e r t y variations and part strength were considered. The most important theoretical a n d practical a s p e c t s lor each modelling stage were i n t r o d u c e d with d u e r e g a r d g i v e n to c o n s t i t u t i v e m o d e l s , a l g o r i t h m s a n d p r e d i c t i o n of m o d e l accuracy.
MODELLING AND D E S I G N OF POWDER METALLURGY CONSOLIDATION PROCESSES T.F. Zahrah, I, C h r i s t o d o u l o u (BI)M Intern a t i o n a l Ine, USA). Process m o d e l s for c o n s o l i d a t i o n to n e a r net s h a p e were d i s c u s s e d w i t h respect to t h e need for a c c u r a c y in p r e d i c t i o n of densification and mechanism of densification. M i e r o m e c h a n i c s m o d e l s for each mechanisms were proposed for hydrostatic and non hydrostatic conditions a n d i n c o r p o r a t e d into a general p u r p o s e finite e l e m e n t p r o g r a m . The objectives were to e x a m i n e t h e m e c h a n i s m s a n d to e x a m i n e t h e c o n t r i b u t i o n of each, t h e predietion of d e n s i t y a n d residual s t r e s s e s a n d to design p r o c e s s schedules.
COMPUTER SIMULATED PROCESS COST MODELS IN POWDER METALLURGY N.V. Nallicheri (IBIS A s s o c i a t e s lnc, USA). Costs in PM p r o c e s s i n g were reviewed with e m p h a s i s on cost-effective h i g h quality m a n u f a c t u r i n g a n d on t h e m e t h o d s used. Traditional m e t h o d s were said to work well under static conditions. The paper considered a dynamic process cost s i m u l a t i o n of t e c h n i c a l cost modelling, which w a s applied to injection moulding,
MPR October 1993 43
An invesligation o1' lhe eflk~cts of h e a t t r e a t m e n t on tim cutting p r o p e r t i e s of WCTiC-TaC Co alloys w a s described. It was reported that repeated thermal shock resulted in decline in s t r e n g t h a n d t h a t t h i s could be p r e v e n t e d by heat t r e a t m e n t . This was atl ributed lo transtkwmation of t h e Co hinder p h a s e from a h e x a g o n a l to a cubic s t r u c t u r e d u r i n g heal t r e a t m e n l a n d the binder was t h e n over s a t u r a t e d }~4th sohlle species. The results of c u t t i n g t e s t s were shown to be in a g r e e m e n t with t h e t h e r m a l shock t c s l s a n d it was d e d u c e d t h a t the h e a t t r e a t m e n t is beneficial in e n h a n c i n g c u t t i n g performance.
E N G I N E E R I N G APPLICATIONS OF DIFFUSION BONDING BRAZING AND HARD FACING FOR HIGH PERFORMANCE TOOLS AND DIES .I.M. l'anchal, T. Vela (Alloy Technology Int lnc, New York, IJSA). The ability of Ferro TiC c o m p o s i t e s to t i n d e r go m a c h i n i n g , h e a t t r e a t m e n t , welding, brazing a n d diffusion b o n d i n g as overlays on tools and dies was d i s c u s s e d w i t h r e s p e c t 1o ( , n h a n ( ' e n / e n l of w e a r properties. The rang(' <)f TiC m a t e r i a l s bonded with steel, tool steel, allot sleel or hard m a t r i x m a t e r i a l s was outlined a n d it was noted lha[ the m a t e r i a l s are being u s e d in aggressive set~.i<-e conditions. Processes a n d a p p l i c a t i o n s were discussed.
T U N G S T E N AND T U N G S T E N BASED COMPOSITES AND ALLOYS FOR HIGH HEAT FLUX DUTY tt.L. Marcus el al (liniversily of Texas, Austin, Texas, USA). An i n v e s t i g a t i o n ~)1 t h e i n f l u e n c e of n/icrostrncttlle o11 n/ass loss fronl ~'-(~11 a n d W Mo alloys u n d e r high heat flux w a s described. The s p e c i n n m s were p r e p a r e d f r o m a l h ) y p o w d e r s , m a d e by r a p i d r e d u c t i o n of ulIral'il/e (helow 200 n m ) oxide powders by cor,ventional p r e s s - a n d s m t e r and high ener~5' r a w m e l h o d s . The h a r d n e s s e s were reported to be higher t h a n commercially available alloys anti t h i s was a t t r i b u t e d to high connectivity a n d Hall l'etch hardening. The results of characterization of heal scarred s u r f a c e s a n d ejected m a t t e r were i n c o r p o r a t e d into a crevice evaporation model. The s t r u c t u r e of l h e W skeleton w a s said lo d e l e r m i n e w h e t h e r
MOLYBDENUM-HAFNIUM-CARBON ALLOYS FOR ELEVATED TEMPERATURE APPLICATIONS R. Daga (Metadyne lnc, USA). The manufacture of p r e c i p i t a t i o n h a r d e n i n g Mo-Hf-C alloys w a s r e p o r t e d and process methods described. The s i n t c r e d billets were l h e r m o m e c h a n i c a l l y p r o c e s s e d into rod a n d wire. C o m p o s i t i o n
LITERATURE
REVIEW
microstructural homogeneity, aging r e s p o n s e a n d m e c h a n i c a l p r o p e r t i e s were evaluated. It was r e p o r t e d t h a t t h e alloys h a d s u p e r i o r elevated t e m p e r a t u r e s t r e n g t h to commercially available Mo alloys.
FABRICATION AND HIGH TEMPERATURE BRAZING OF MOLYBDENUM-RHENIUM ALLOYS J.A. Shiehts et al ( C l i m a x Speciality Metals, Cleveland, Ohio, USA). T h e m a n u f a c t u r e of a n a e r o s p a c e c o m p o n e n t by m a c h i n i n g from a s i n t e r e d Mo alloy plate a n d a s i n t e r e d Mo-Re alloy t u b e a n d a Mo manifold, which were brazed together, at 700 C, w a s described. T h e c o m p o n e n t w a s i n t e n d e d to w i t h s t a n d severe vibration and thermal and m e c h a n i c a l s h o c k in a m a n n e d s p a c e vehicle. Production and testing were discussed.
Modelling and computational methods A REVIEW OF NUMERICAL AND COMPUTATIONAL T E C H N I Q U E S IN POWDER METALLURGY R.M. G e r m a n (t'ennsTlvania State University, Pennsylvania, USA). The use of n u m e r i c a l a n d c o m p u t a t i o n a l m e t h o d s for t h e m o d e l l i n g of PM u n i t p r o c e s s e s a n d o p e r a t i o n s w a s critically reviewed with reference to a t o m i z a t i o n , c o m p a c t i o n , sintering, injection m o u l d i n g , HIP a n d powder forging, The a p p l i c a t i o n s of c o m p u t e r s to p a r t design p r o c e s s control, d a t a collection a n d image analysis were discussed. The range of a p p l i c a t i o n from pairing of a t o m s to entire m a n u f a c t u r i n g sites were outlined with m e n t i o n of finite element analysis, statistics, modelling, management and knowledge based sTstems being c o n s i d e r e d in t h e light of t h e state-of-the-art.
EXPERIMENTAL D E S I G N AND RELATED STATISTICAL M E T H O D S IN E X P E D I T I N G TECHNICAL SOLUTIONS IN PARTICULATE TECHNOLOGY C.I. W']fitman (SSI M a n a g e m e n t Consult a n t s Inc, USA). Technical c h a l l e n g e s a n d s o l u t i o n s in particulate technology, ranging from trouble s h o o t i n g to d e v e l o p m e n t of new p r o c e s s e s a n d p r o d u c t s were 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 given to e x p e r i m e n t a l design, s t a t i s t i c a l m o d e l l i n g a n d p r o p e r t i e s of m a t e r i a l s . T h e v a l u e of t h e p e r s o n a l c o m p u t e r in p o w d e r m e t a l l u r g y w a s e m p h a s i s e d w i t h r e s p e c t to t h e available software.
APPLICATION OF COMPUTER A I D E D D E S I G N AND MANUFACTURING IN THE PM PARTS INDUSTRY B.A. Stebick (Windfall P r o d u c t s Inc, St Mary's, Penns?dvania, USA).
A c a s e s t u d y , w h i c h w a s s a i d to e m p h a s i s e t h e value of CAI)/CAM in t h e d e v e l o p m e n t , design a n d m a n u f a c t u r e of a PM c o m p o n e n t was p r e s e n t e d . It w a s noted t h a t CAD/CAM h a s h a d a significant effect on all a s p e c t s of PM fabrication.
MODELLING OF TItE POWDER METALLURGY P R O C E S S A. Lawley, B.L. F e r g u s o n ( l ) e f l ) r m a t i o n Control Technology Inc, USA). A critical a p p r a i s a l of m o d e l s of a wide range o f PM u n i t p r o c e s s e s and m e c h a n i s m s w a s presented. E m p h a s i s w a s p l a c e d on t h e i m p o r t a n c e of a c c u r a t e p r o c e s s d e s c r i p t i o n to o p t i m i s e t h e m a n u f a c t u r i n g cycle with t h e objective of u s i n g real t i m e p r o c e s s control.
INTEGRATED COMPUTER A I D E D D E S I G N AND ANALYSIS OF POWDER METALLURGY PRODUCTS M. Guillot et al (Laval Uniwxsity, C a n a d a ) . An i n t e g r a t e d c o m p u t e r aided e l e m e n t m e t h o d a p p r o a c h for design a n d analysis of PM p a r t s was presented. Density d i s t r i b u t i o n s , die filling time, (:racking d u r i n g c o m p a c t i o n a n d ejection, p r o p e r t y variations and part strength were considered. The most important theoretical a n d practical a s p e c t s lor each modelling stage were i n t r o d u c e d with d u e r e g a r d g i v e n to c o n s t i t u t i v e m o d e l s , a l g o r i t h m s a n d p r e d i c t i o n of m o d e l accuracy.
MODELLING AND D E S I G N OF POWDER METALLURGY CONSOLIDATION PROCESSES T.F. Zahrah, I, C h r i s t o d o u l o u (BI)M Intern a t i o n a l Ine, USA). Process m o d e l s for c o n s o l i d a t i o n to n e a r net s h a p e were d i s c u s s e d w i t h respect to t h e need for a c c u r a c y in p r e d i c t i o n of densification and mechanism of densification. M i e r o m e c h a n i c s m o d e l s for each mechanisms were proposed for hydrostatic and non hydrostatic conditions a n d i n c o r p o r a t e d into a general p u r p o s e finite e l e m e n t p r o g r a m . The objectives were to e x a m i n e t h e m e c h a n i s m s a n d to e x a m i n e t h e c o n t r i b u t i o n of each, t h e predietion of d e n s i t y a n d residual s t r e s s e s a n d to design p r o c e s s schedules.
COMPUTER SIMULATED PROCESS COST MODELS IN POWDER METALLURGY N.V. Nallicheri (IBIS A s s o c i a t e s lnc, USA). Costs in PM p r o c e s s i n g were reviewed with e m p h a s i s on cost-effective h i g h quality m a n u f a c t u r i n g a n d on t h e m e t h o d s used. Traditional m e t h o d s were said to work well under static conditions. The paper considered a dynamic process cost s i m u l a t i o n of t e c h n i c a l cost modelling, which w a s applied to injection moulding,
MPR October 1993 43