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Viscosity of powder suspensions
p r o t e c t i o n a n d use of m i n i m u m force required to produce quality parts, c o n f e r r e d by force m e a s u r e m e n t s was discussed. A description was given of t h e systems for force m e a s u r e m e n t a n d control systems covering all aspects of pressing. It was r e p o r t e d t h a t t h e systems allowed analysis of press condition a n d reduction of set-up time a n d m a i n t e n a n c e costs. TOOL LOAD MONITORING SYSTEM FOR MULTI-LEVEL COMPACTION PRESS
R.F. Unkel, R. Burns (Cincinnati Inc, Ohio, USA). A tool load monitoring system for multilevel compaction presses was described. The system allows for t h e m o n i t o r i n g of p a r t - t o - p a r t variations. The operation of t h e system a n d its use for quality a s s u r a n c e were described.
Powder injection moulding HOMOGENEITY OF F E E D S T O C K IN POWDER INJECTION MOULDING
R.M. G e r m a n et al (Pennsylvania State University, Pennsylvania, USA). An investigation of homogeneity of IM f e e d s t o c k w a s d e s c r i b e d . A r a n g e of techniques was used a n d it was reported t h a t c a p i l l a r y r h e o m e t r y was t h e b e s t m e a n s of d e t e r m i n i n g t h e state of o r d e r in t h e feedstock, r e p r e s e n t e d by the viscosity. T h r e e b a t c h e s of f e e d s t o c k w i t h high, medium and low homogeneity were processed under identical moulding, d e b i n d i n g a n d sintering conditions. The specimens were evaluated at each stage a n d t h e results of tests related to t h e homogeneity levels. EXTRUSION PLASTOMETER T E S T I N G OF METAL INJECTION MOULDING FEEDSTOCK
K.M. Kulkarni, G. Eberl (Advanced Metalworking Practices Inc, Carmel, Indiana, USA). Use of a deadweight extrusion p l a s t o m e t e r for a s s e s s m e n t of viscosity of IM f e e d s t o c k , a s a n i n d i c a t i o n of mouldability, was described. The t e c h n i q u e was r e p o r t e d to be a useful m e a n s of communicating data between feedstock a n d p a r t s manufacturers.
VISCOSITY OF POWDER S U S P E N S I O N S
J.A. Horn, B.R. P a t t e r s o n (University of Alabama, Birmingham, Alabama, USA). A model for t h e viscosity of suspensions, in t e r m s of hydrodynamics, mechanical, electrostatic a n d interparticle interactions was d e s c r i b e d . The m o d e l w a s t e s t e d against mixtures with variable c o m p o s i t i o n a n d d i s p e r s i o n a n d good a g r e e m e n t was reported. The model was said to provide a n insight into t h e effects of process variables and interparticle interactions on the viscosity of mixtures. CERAMIC INJECTION MOULDING WITH A POLYACETYL BASED B I N D E R SYSTEM
J.S. Ebenhock, J.H. t e r Maat (BASF AG, Ludwigshafen, Germany). It was r e p o r t e d t h a t a n IM feedstock, c o n t a i n i n g a polyacetyl resin as b i n d e r instead of wax, h a d been developed. The new b i n d e r was said to have t h e a d v a n t a g e s of high green strength, no de-mixing during moulding and a high debinding rate w i t h o u t distortion. The m a n u f a c t u r e of ceramic p a r t s was discussed with regard to defects which can occur at any stage. IM a n d HIP were c o m p a r e d with respect to t h e incidence of flaws. REACTIVE B I N D E R METAL INJECTION MOULDING OF IRON-BASE POWDERS
A. Lawley et al (Drexel University, USA). A t t e n t i o n was drawn to t h e difficulty in MIM of forming complex s h a p e d p a r t s due to i n a d e q u a t e flow p r o p e r t i e s of t h e feedstock leading to density variations, shrinkage a n d distortion d u r i n g d e b i n d i n g and the cost of equipment and i n s t r u m e n t a t i o n . The use of a gravity feed system and a emtal powder/reactive polymer b i n d e r m i x t u r e in t h e p r o d u c t i o n of m o u l d cavities was described. Reaction between powder a n d b i n d e r occurs a n d is r e p o r t e d to yield c o m p a c t s with good green strength. A feasibility study using stainless steel a n d ceramic powders was carried out a n d no volume change was detected d u r i n g d e b i n d i n g a n d 2 to 3% c h a n g e d u r i n g sintering was recorded. Results from u n i a x i a l c o m p a c t i o n e x p e r i m e n t s were used to assess feasibility of t h e use of isostatic pressing for intricately s h a p e d parts.
COMPUTER ANALYSIS OF FLUID FLOW AND HEAT TRANSFER IN METAL INJECTION MOULDING
SINTERING OF INJECTION MOULDED LOW ALLOY S T E E L S
C. Wang et al ( C o n c u r r e n t Technologies Corp, USA). A c o m p u t e r s i m u l a t i o n p r o g r a m for prediction of mould filling a n d feedstock freezing in MIM was described. The model was reported to allow prediction of defect formation. A comparison of predicted a n d e x p e r i m e n t a l results was p r e s e n t e d using 3-dimensional colour graphics.
M. Bloemacher, D. Weinand (BASF AG, Ludwigshafen, Germany). The use of MIM to produce low alloy steel p a r t s was discussed with respect to t h e powders used including fine powders, atomized highly alloyed powders a n d Fe-Ni mixtures. The cost of fine powders was said to be high c o m p a r e d with raw m a t e r i a l s costs a n d Fe-Ni m i x t u r e s are often used. The p a p e r reported studies of MIM p a r t s
42 MPR October 1993
m a d e from elemental p o w d e r blends using carbonyl Fe p o w d e r a n d a novel feedstock system coupled with catalytic debinding. S i n t e r i n g a n d diffusion b e h a v i o u r a n d h a r d e n i n g r e s p o n s e were evaluated. D E B I N D I N G AND SINTERING OF MIM 316L STAINLESS S T E E L PARTS
D.P. Duncavage, C.W. Finn ( N o r t h e a s t e r University, USA). It was suggested t h a t t h e MIM of low C stainless steel p a r t s shows considerable potential. Application is h i n d e r e d by t h e high b i n d e r c o n t e n t of t h e feedstock (above 30%), formation of oxides, nitrides a n d carbides a n d loss of Cr by evaporation. It was r e p o r t e d t h a t a t m o s p h e r e control h a s resulted in s i m u l t a n e o u s oxide reduction a n d decarburization. Inert gas backfill a n d n e a r liquid p h a s e sintering were r e p o r t e d to yield h i g h d e n s i t i e s , good m e c h a n i c a l p r o p e r t i e s a n d to m a i n t a i n c o r r o s i o n resistance.
ACTIVATED INFILTRATION SINTERING OF INJECTION MOULDED TUNGSTEN-COPPER-NICKEL ALLOYS
B. Yang, R.M. German (Pennsylvania State University, Pennsylvania, USA). The effects of a d d i n g 0.5% Ni to injection m o u l d e d W-19.5% Cu alloys were described. The Ni a d d i t i o n was r e p o r t e d to result in improved sintering and mechanical properties. For a n alloy of 99.5% density t h e Vickers h a r d n e s s was 348 a n d t h e t r a n s v e r s e r u p t u r e s t r e n g t h 1523 MPa after infiltration sintering. The effects of infiltration sintering a n d W a n d Cu particle sizes on s i n t e r i n g a n d p r o p e r t i e s were discussed t o g e t h e r with t h e MIM process a n d results.
Refractory metals PERFORMANCE OF SHOCK S Y N T H E S I S E D DIAMOND ABRASIVE POWDERS
D.R. Bergmann, N.F. Bailey (DuPont Co, Wilmington, Delaware, USA). Explosive shock synthesis of polycrystalline diamond powder from g r a p h i t e was described. The properties of t h e powder were c o m p a r e d with n a t u r a l and static pressure synthetic diamond particularly abrasive performance a g a i n s t saphire. Industrial applications were discussed. E F F E C T S OF HEAT T R E A T M E N T ON THERMO-MECHANICAL SHOCK P R O P E R T I E S OF MIXED T U N G S T E N / TITANIUM/TANTALUM CARBIDESCOBALT ALLOYS FOR I N T E R M I T T E N T CUTTING
J. Wu et al ( S h a n g h a i Research Inst of Materials, Shanghai, China).
R.F. Unkel, R. Burns (Cincinnati Inc, Ohio, USA). A tool load monitoring system for multilevel compaction presses was described. The system allows for t h e m o n i t o r i n g of p a r t - t o - p a r t variations. The operation of t h e system a n d its use for quality a s s u r a n c e were described.
Powder injection moulding HOMOGENEITY OF F E E D S T O C K IN POWDER INJECTION MOULDING
R.M. G e r m a n et al (Pennsylvania State University, Pennsylvania, USA). An investigation of homogeneity of IM f e e d s t o c k w a s d e s c r i b e d . A r a n g e of techniques was used a n d it was reported t h a t c a p i l l a r y r h e o m e t r y was t h e b e s t m e a n s of d e t e r m i n i n g t h e state of o r d e r in t h e feedstock, r e p r e s e n t e d by the viscosity. T h r e e b a t c h e s of f e e d s t o c k w i t h high, medium and low homogeneity were processed under identical moulding, d e b i n d i n g a n d sintering conditions. The specimens were evaluated at each stage a n d t h e results of tests related to t h e homogeneity levels. EXTRUSION PLASTOMETER T E S T I N G OF METAL INJECTION MOULDING FEEDSTOCK
K.M. Kulkarni, G. Eberl (Advanced Metalworking Practices Inc, Carmel, Indiana, USA). Use of a deadweight extrusion p l a s t o m e t e r for a s s e s s m e n t of viscosity of IM f e e d s t o c k , a s a n i n d i c a t i o n of mouldability, was described. The t e c h n i q u e was r e p o r t e d to be a useful m e a n s of communicating data between feedstock a n d p a r t s manufacturers.
VISCOSITY OF POWDER S U S P E N S I O N S
J.A. Horn, B.R. P a t t e r s o n (University of Alabama, Birmingham, Alabama, USA). A model for t h e viscosity of suspensions, in t e r m s of hydrodynamics, mechanical, electrostatic a n d interparticle interactions was d e s c r i b e d . The m o d e l w a s t e s t e d against mixtures with variable c o m p o s i t i o n a n d d i s p e r s i o n a n d good a g r e e m e n t was reported. The model was said to provide a n insight into t h e effects of process variables and interparticle interactions on the viscosity of mixtures. CERAMIC INJECTION MOULDING WITH A POLYACETYL BASED B I N D E R SYSTEM
J.S. Ebenhock, J.H. t e r Maat (BASF AG, Ludwigshafen, Germany). It was r e p o r t e d t h a t a n IM feedstock, c o n t a i n i n g a polyacetyl resin as b i n d e r instead of wax, h a d been developed. The new b i n d e r was said to have t h e a d v a n t a g e s of high green strength, no de-mixing during moulding and a high debinding rate w i t h o u t distortion. The m a n u f a c t u r e of ceramic p a r t s was discussed with regard to defects which can occur at any stage. IM a n d HIP were c o m p a r e d with respect to t h e incidence of flaws. REACTIVE B I N D E R METAL INJECTION MOULDING OF IRON-BASE POWDERS
A. Lawley et al (Drexel University, USA). A t t e n t i o n was drawn to t h e difficulty in MIM of forming complex s h a p e d p a r t s due to i n a d e q u a t e flow p r o p e r t i e s of t h e feedstock leading to density variations, shrinkage a n d distortion d u r i n g d e b i n d i n g and the cost of equipment and i n s t r u m e n t a t i o n . The use of a gravity feed system and a emtal powder/reactive polymer b i n d e r m i x t u r e in t h e p r o d u c t i o n of m o u l d cavities was described. Reaction between powder a n d b i n d e r occurs a n d is r e p o r t e d to yield c o m p a c t s with good green strength. A feasibility study using stainless steel a n d ceramic powders was carried out a n d no volume change was detected d u r i n g d e b i n d i n g a n d 2 to 3% c h a n g e d u r i n g sintering was recorded. Results from u n i a x i a l c o m p a c t i o n e x p e r i m e n t s were used to assess feasibility of t h e use of isostatic pressing for intricately s h a p e d parts.
COMPUTER ANALYSIS OF FLUID FLOW AND HEAT TRANSFER IN METAL INJECTION MOULDING
SINTERING OF INJECTION MOULDED LOW ALLOY S T E E L S
C. Wang et al ( C o n c u r r e n t Technologies Corp, USA). A c o m p u t e r s i m u l a t i o n p r o g r a m for prediction of mould filling a n d feedstock freezing in MIM was described. The model was reported to allow prediction of defect formation. A comparison of predicted a n d e x p e r i m e n t a l results was p r e s e n t e d using 3-dimensional colour graphics.
M. Bloemacher, D. Weinand (BASF AG, Ludwigshafen, Germany). The use of MIM to produce low alloy steel p a r t s was discussed with respect to t h e powders used including fine powders, atomized highly alloyed powders a n d Fe-Ni mixtures. The cost of fine powders was said to be high c o m p a r e d with raw m a t e r i a l s costs a n d Fe-Ni m i x t u r e s are often used. The p a p e r reported studies of MIM p a r t s
42 MPR October 1993
m a d e from elemental p o w d e r blends using carbonyl Fe p o w d e r a n d a novel feedstock system coupled with catalytic debinding. S i n t e r i n g a n d diffusion b e h a v i o u r a n d h a r d e n i n g r e s p o n s e were evaluated. D E B I N D I N G AND SINTERING OF MIM 316L STAINLESS S T E E L PARTS
D.P. Duncavage, C.W. Finn ( N o r t h e a s t e r University, USA). It was suggested t h a t t h e MIM of low C stainless steel p a r t s shows considerable potential. Application is h i n d e r e d by t h e high b i n d e r c o n t e n t of t h e feedstock (above 30%), formation of oxides, nitrides a n d carbides a n d loss of Cr by evaporation. It was r e p o r t e d t h a t a t m o s p h e r e control h a s resulted in s i m u l t a n e o u s oxide reduction a n d decarburization. Inert gas backfill a n d n e a r liquid p h a s e sintering were r e p o r t e d to yield h i g h d e n s i t i e s , good m e c h a n i c a l p r o p e r t i e s a n d to m a i n t a i n c o r r o s i o n resistance.
ACTIVATED INFILTRATION SINTERING OF INJECTION MOULDED TUNGSTEN-COPPER-NICKEL ALLOYS
B. Yang, R.M. German (Pennsylvania State University, Pennsylvania, USA). The effects of a d d i n g 0.5% Ni to injection m o u l d e d W-19.5% Cu alloys were described. The Ni a d d i t i o n was r e p o r t e d to result in improved sintering and mechanical properties. For a n alloy of 99.5% density t h e Vickers h a r d n e s s was 348 a n d t h e t r a n s v e r s e r u p t u r e s t r e n g t h 1523 MPa after infiltration sintering. The effects of infiltration sintering a n d W a n d Cu particle sizes on s i n t e r i n g a n d p r o p e r t i e s were discussed t o g e t h e r with t h e MIM process a n d results.
Refractory metals PERFORMANCE OF SHOCK S Y N T H E S I S E D DIAMOND ABRASIVE POWDERS
D.R. Bergmann, N.F. Bailey (DuPont Co, Wilmington, Delaware, USA). Explosive shock synthesis of polycrystalline diamond powder from g r a p h i t e was described. The properties of t h e powder were c o m p a r e d with n a t u r a l and static pressure synthetic diamond particularly abrasive performance a g a i n s t saphire. Industrial applications were discussed. E F F E C T S OF HEAT T R E A T M E N T ON THERMO-MECHANICAL SHOCK P R O P E R T I E S OF MIXED T U N G S T E N / TITANIUM/TANTALUM CARBIDESCOBALT ALLOYS FOR I N T E R M I T T E N T CUTTING
J. Wu et al ( S h a n g h a i Research Inst of Materials, Shanghai, China).