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Structural characteristics of atomised white cast iron powder
S t r n c t u r e a n d t h e r m a l s t a b i l i t y of t h e mille(l p()w(ters w e r e d e t e r m i n e d by eh~ctrnn microscopy, X ray difli'action and differentiai s c a n n i n g calorimetk~" a n d gas a b s o r b t i o n by p r e s s u r e r e d u c t i o n in t h e mill. h was found thai large a m o u n t s of N a r c a b s o r b e d d u r i n g m i l l i n g in a N c o n t a i n i n g a t m o s p h e r e a c ( o l n p a n i e d bv s t r u c t u r a l refinement a n d a m o r p h i s a t i o n CreN was forlne(t oil a n n e a l i n g . A m o r p h i z a t i o n did not occur on milling inAr or Ar 0 m i x t u r e s . Art e x p l a n a l i o n in t e r m s of t h e r m o d y n a n l i c s is given
Cobalt SINTERING CHARACTERISTICS ULTRAFINE COBALT POWDER
OF
Y Sakka, (National I~'esearch inst.ilute for Metals, ,lapan). J. Less Commo'** Metals.
tqd 168, No 2, 1991, 2772,S'7. The s i m e r i n g of u l t r a l i n e ( n powders in vacuunl an(t t[ was nlorlilored hv s t r u c t u r a l a n d d i m e n s i o n a l changes. The p r e s e n c e of i n c l u ( t e d o x i d e s h i n d e r s s i n l e r i n g il, vacuunl but in H t h e o x i d e s are reduced and significant (tensifi(:ation occurs. Gases are evolve(I d u r i n g ~ a c u u m s i n t e r i n g a n d t h e s e were identified as Co e, CO, tie a n d lift). Surface condit;ions are d i s c u s s e d by c o n s i d e r a t i o n of t h e (h~sort)tion sl)ectra.
Copper FACTORS INFLUENCING THE QUALITY OF E L E C T R O I N T I C C O P P E R P O W D E R A. I)urisinova, (Sh)vak A(:a(lemy of Sciences, K(,sice C z e c h o s h ) v a k i a ) , P o w d e r
Metallurgy, Vol 33, No 2, 199l. 139 141. The eflbcts of tint(! of growlh, current d e n s i l y , eleci r o l y t e c o m p o s i t i o n a n d len~l)eralure pll. c i r c u l a l i o n ()I" t h e electrolyte a n d l h e p r e s e n c e of i m p u r i t i e s on the quality of e l e c t r o l ~ i c Cu p o w d e r s have heen stu(lied. C h a n g e s in p o w d e r properties were delermined and the powders were e x a m i n e d microscopically.
Iron a n d S t e e l THE WORKABILITY OF POROUS STEEL PREFORMS A. El I)omialy, M. Shaker. (Suez Canal University, Egypt), ,L Materials Processin.q
Technology, Vol 25, No 2, 1991, 2 2 9 233. A t t e n t i o n is drawn to a m a j o r limitation of powder forging of steel, cracking in t h e (tie. A m e t h o d of c h a r a c l e r i s i n g workability h a s been developed for w r o u g h t m e t a l s a n d applied to p o r o u s metals. Workability limits for s i n t e r e d Fe-0.2%C-0.5%Mo-0.04%S0.04%P w i t h d i f f e r e n t p o r o s i t i e s w e r e d e t e r m i n e d a n d it w a s d e d u c e d t h a t porosity is the m a i n p a r a m e t e r controlling workability of p o r o u s materials.
EFFECT OF SINTERING CONDITIONS ON ISOTHERMAL DECOMPOSITION OF AUTENITE IN SINTERED STEELS V.N. Antsiferov et al, Stal', No 12, 1990, 84-
ferro-alloys are u s e d in p r o d u c t i o n of steels. The p a p e r r e p o r t s on how ferro-alloys influence properties structure and sintering charaeleristics of s i n t e r e d ferrous alloys.
87. In R~ssian. The isothermal decomposition of A u s t e n i t e in PM steels c o m a i n i n g either 1.0 to 1.5%C a n d 3%Cu or" 1.0%C a n d 1.0%Mn was investigated with respect to the s i n t e r i n g a t m o s p h e r e . The s t r u c t u r e s were e x a m i n e d a n d it was l o u n d t h a t on s i n t e r i n g in s t a g n a n t a t m o s p h e r e s a e e m t i t e network w a s f o r m e d a n d t h e r e were g r a p h i t e i n c l u s i o n s w h i c h n u c l e a t e d the b r e a k d o w n of A u s t e n i t e t h i s r e d u c i n g the. i n c u b a t i o n period. It w a s found t h a t t h e C-Cu steel required a double heat treatmenl aud requench quench from 860 C a n d t e m p e r i n g at 300~C to a t t a i n greater s t r e n g t h . EFFECTS OF PRODUCTION PARAMETERS ON STRUCTURE AND PROPERTIES OF REDUCED AND ATOMISED IRON POWDERS 1.P. Argent'seva et al, (Moscow Evening Metallurgical Institute, USSR), Stal', No 11,
1990, 87-92. b~ Ru,ssiar~. The s t r u c t u r e a n d p r o p e r t i e s of r e d u c e d a n d a t o m i s e d Fe powders were investigated. Powder surface morpholog5 ~ a n d O c o n t e n t in relation t.o compactibility are d i s c u s s e d with respecl to t h e f o r m a t i o n of interparticle c o n t a c t s d u r i n g p r e s s i n g a n d s t r e n g t h a n d d e n s i t y of t h e c o m p a c t s . ULTRA HIGH STRENGTH FERROUS COMPONENTS
SINTERED
O. Durukimi et al, (Kawasaki Steel Corporation, Kawasaki, J a p a n ) , D~t J. P o w d e r
Metall,Jrgy, Vol 27, No 4, 1991, 331-337. A newly developed steel c o n t a i n i n g 2%Ni a n d l%Mo with tensile s t r e n g t h 1500 MPa, impact s t r e n g t h 21J, r o t a t i n g b e n d fatigue s t r e n g t h 460 MPa a n d c o m p a c t fatigue s t r e n g t h 2560 MPa is described. It w a s r e p o r t e d t h a t p r o p e r t i e s couM be i n c r e a s e d by double pressing, resintering, h a r d e n i n g a n d tempering. The i n c r e a s e d s t r e n g t h s are a t t r i b u t e d to a s t r a i n i n d u c e d m a r t e n s i t i c t r a n s f o r m a t i o n in t h e r e t a i n e d Austenite.
ENHANCED SINTERING AND PROPERTY IMPROVEMENTS IN SINTERED FERROUS COMPONENTS D.S. Madan, (Elkem D e v e l o p m e n t Centre, Sewiekley, P e n n s y l v a n i a , U S A ) , I n t J.
P o w d e r Metallurgy, Vol 27, No 4, 1991, 339-345. M o d e l s of e n h a n c e d s i n t e r i n g a r e reviewed a n d t h e role of a d d i t i o n s of ferro-alloys to PM steels is discussed. The m e c h a n i c a l a n d p h y s i c a l p r o p e r t i e s of w a t e r a t o m i s e d DFe p o w d e r alloyed with h i g h p u r i t y f e r r o - p h o s p h o r o u s or ferroboron are described. The p r o p e r t i e s are shown to be s u p e r i o r w h e n high p u r i t y
IMPROVED PROPERTIES AND P E R F O R M A N C E O F LOW ALLOY S T E E L PARTS THROUGH HIGH TEMPERATURE SINTERING K. S h i m a d a , (Tokyo Sintered Metals Corporation, Tokyo, .Japan), [nt J. P o w d e r
Metallurgy, Vol 27, No 4, /991, 357-361. S u p e r i o r s t r e n g t h , fatigue p r o p e r t i e s a n d w e a r r e s i s t a n c e are r e p o r t e d to have been a t t a i n e d in low alloy st,eel PM p a r t s by s i n t e r m g at 1250:C, carburising, h a r d e n i n g a n d tempering. The p r o p e r l y i m p r o v e m e n t s a r e a t t r i b u t e d to p o r o s i t y r e d u c t i o n , s p h e r o i d i s a t i o n of r e s i d u a l p o r e s a n d increased neck growth d u r i n g sintering. A u t o m o t i v e a p p l i c a t i o n s a r ( discussed. NEW SINTERED STEELS CONTAINING HARD PHASES FOR WEAR RESISTANT APPLICATIONS F. Thfimmler, C. Gutsfeld. (University ol Karlsruhe, Karlsruhe, G e r m a n y ) , P o w d e r
Metall. Int, Vol 23, No 5, /991, 285-290. T h e p r o d u c t i o n of Fe b a s e d m e t a l m a t r i x c o m p o s i t e s (MMC', c o n t a i n i n g 10 to 30vo>,; of h a r d plrases NbC. TiC of AI~O:~, u s i n g m e c ' h a n i c a l a l l o y i n g (MA) to incorporate the hard phase and sintering at 128()"C in H is d e s c r i b e d The a d d i t i o n of C or P to create a liquid ptmse d u r i n g s i n t e r i n g resulted in d e n s i t i e s of 97 to 99?,; a n d a u n i f o r m d i s t r i b u t i o n of t h e h a r d particles was d u e to t h e ~se of MA. The mechanical properties and wear c h a r a c t e r i s t i c s were, shown to d e m o n s t r a t e t h e p o t e n t i a l of t h e m a t e r i a l s lot u s e in wear resistant applications
PROPERTIES OF WATER ATOMISED IRON POWDER CONTAINING PHOSPHOROUS AND CARBON OR BORON AND SILICON T. Sato et al, J. Materials Science, Vol 26,
No 9, 1991, 2329-2336. The mierostructure and powder p r o p e r t i e s of w a t e r a t o m i s e d Fe-P-C a n d Fe-B-Si a l l o y s w e r e i n v e s t i g a t e d w i t h respect to glass f o r m i n g conditions. The metallic glass p o w d e r s h a d not flowability. It w a s also found t h a t p a r t i c l e s b e c a m e m o r e irregular as t h e size increased. In crystalline powders both ~ and intermetallic p h a s e s were found in hypoa n d hyper-eutectic ;alloys.
STRUCTURAL CHARACTERISTICS ATOMISED WHITE CAST IRON POWDER
OF
A.P. Gulyaev et al, Metalloved. Term. Obrab
Met, No 1, 1991, 34-35. I~ R u s s i a n .
MPR February 1992 57
i~
The structures of atomised white cast iron powders containing 2.5 to 4.5%C and solidified at 10 to 105°C/sec were studied. The structures were very different from those of normal white cast iron. Increased cooling rate reduced the vol fraction of eutectic but at 3.9%C the structure was wholly eutectic. The structure was refined by i n c r e a s e d cooling rate. The r a p i d l y cooled Austenite was s a t u r a t e d with C. E F F E C T S OF H E A T I N G M E T H O D D U R I N G S I N T E R I N G ON S T R U C T U R E A N D P R O P E R T I E S OF IRON-BASE MATERIALS
N.A. Nikishov et al, Metalloved
Term. Obrab. Met, No 1, 1991, 35-37. In Russian.
The structure, p h a s e composition and mechanical p r o p e r t i e s of s i n t e r e d rings made from Fe-l.8%C-2.9%Cr-l.9%Cu or an alloy containing a special Cr carbide in addition to 0.6%C were described. Process conditions are stated. Induction sintering was r e p o r t e d to yield a p r o d u c t of better quality. E F F E C T S OF A D D I T I O N S OF ALKALI METAL C O M P O U N D S O N S T R U C T U R E A N D P R O P E R T I E S OF PM CARBON STEEL
L.N. D'yachkov et al, Metalloved
Term Obrab met, No 1, 1991, 37-39. In Russian.
The addition of bicarbonates of Na, K or Li to a PM steel with 0.5 to 0.55%C was found to accelerate diffusion of C in the steel, increase the a m o u n t of C retained and yield a m o r e h o m o g e n e o u s s t r u c t u r e , particularly at low sintering temperatures. Improved mechanical properties were reported when alkali bicarbonate additions in the range 0.2 to 0.5% were made. Sintering of the compacted powders was in the range 950 to 1250°C for 2 hours. E F F E C T OF S I N T E R I N G C O N D I T I O N S ON T H E M E C H A N I C A L P R O P E R T I E S OF M E T A L I N J E C T I O N M O U L D E D (MIM) STAINLESS STEEL
M. Tsuda, H. Kyogoju, J. J a p a n Soe Powder
and Powder Metallurgy, Vol 38, No 4, 1991, 523-528. In Japanese. The effects of sintering conditions on the density and mechanical properties of MIM 304L s t a i n l e s s steel w e r e investigated. Density was increased by increased time and/or temperature. Specimens were cooled e i t h e r in N or vacuum. The N cooled specimens had higher h a r d n e s s an s t r e n g t h which were a t t r i b u t e d to nitride formation at the surface. E F F E C T S OF B O R I D E A D D I T I O N S ON S I N T E R I N G OF A U S T E N T I T I C STAINLESS STEEL POWDER COMPACTS M. Kamada et al, J. J a p a n Soc Powder and
Powder Metallurgy, Vol 38, NO 2, 1991, 529-534. In Japanese. 58
MPR
February
1992
PMLITERATURE
REVIEW
The effects of b o r i d e a d d i t i o n s on d e n s i f i c a t i o n o f 304L s t a i n l e s s s t e e l powder were studies with respect to liquid p h a s e sintering. CrB t r a n s f o r m s the Cr3B d u r i n g s i n t e r i n g a n d a e u t e c t i c liquid between this and the m a t r i x p h a s e forms. Small pores were found to d i s a p p e a r but large ones remained and t h e s e were said to be located at the site of the original CrB particles. The liquid p h a s e is r e p o r t e d to aid in densification and solidifies to Cr2B plus Austenite. Similar results are reported for FeB and NiB additions. E F F E C T S OF CARBON C O N T E N T O N S I N T E R I N G BEHAVIOUR A N D T E N S I L E P R O P E R T I E S OF S I N T E R E D MARTENSITIC STAINLESS STEELS
M. Kamada, Y. Tokunaga, J. J a p a n
Soc Powder and Powder Metallurgy, Vol 38, No 2, 1991, 535-539. In Japanese. The effects of carbon content, sintering t e m p e r a t u r e and heat t r e a t m e n t conditions on the p r o p e r t i e s on sintered martensitic 410L stainless steel were investigated. It was reported t h a t the vol fraction of ferrite at the s i n t e r i n g t e m p e r a t u r e d e c r e a s e s w i t h i n c r e a s e in %C a n d decrease in sintering temperature, aferrite is said to aid d e n s i f i c a t i o n a n d p o r e r o u n d i n g due to high self diffusion. A m i n i m u m of 0.1%C is required to produce a martensitic structure. Strength increases with %C due to e n h a n c e d densiflcation.
Molybdenum B O R O N I S I N G T R E A T M E N T FOR SINTERED MOLYBDENUM-NICKEL POWDER COMPACTS
T. Sakamoto. J. J a p a n Soe Powder and
Powder Metallurgy, Vol 38, No 4, 1991, 492-498. In Japanese. Boronising using BoB, NiB and B4C in an a c t i v a t o r c o n t a i n i n g NH4C1, BaF3 or Na2CO3, of sintered Mo and Mo-38% was investigated. The b o r o n i s e d alloys were e x a m i n e d by X-ray diffraction and electron probe micro analysis (EPMA). It was found t h a t the thickness of the boronised layers increased with time a n d / o r temperature. The layers c o n t a i n e d MoB, Mo2B a n d Mo2B5. The c h l o r i d e or f l u o r i d e w e r e identified w h e n p r e s e n t in the activator. NiB powder was not found to increase the boride layer thickness.
Titanium P R O D U C T I O N OF T I T A N I U M BASE M E T A L MATRIX C O M P O S I T E S ( M M C ) BY VACUUM PLASMA SPRAYING
P.A. Dearnley, K.A. Roberts, (University of Cambridge, Cambridge, England), Powder Metallurgy, Vol 34, No 2, 1991, 112-118.
~
The p r o d u c t i o n of Ti-base MMC by vacuum p l a s m a spraying has been studied by high s p e e d cinematography. The p l a s m a was found to show fluctuations in length. The m e c h a n i s m of co-spray deposition has been elucidated by use of a wipe test and is d e s c r i b e d as e m b e d d i n g of c e r a m i c p a r t i c l e s into t h e s u b s t r a t e f o l l o w e d by covering w i t h Ti splats. M e t a l / c e r a m i c collisions in flight are r e p o r t e d to be of small significance. MICROSTRUCTURE AND MECHANICAL P R O P E R T I E S OF R E S I S T A N C E SINTERED TITANIUM
C.H. Lui, P.W. Kao, Scripta MetaU Mater,
Vol 24 No 12, 1990, 2279-2284. An i n v e s t i g a t i o n into t h e r e s i s t a n c e s i n t e r i n g o f Ti, w h i c h s h o w e d r a p i d d e n s i f i c a t i o n to d e n s i t y above 96% in a b o u t 2 s e c o n d s , is d e s c r i b e d . T h e r e s i s t a n c e s i n t e r e d Ti was r e p o r t e d to have higher s t r e n g t h t h a n conventional PM Ti. T h e r a p i d d e n s i f i c a t i o n is attributed to the formation of a liquid p h a s e at p a r t i c l e b o u n d a r i e s w h i c h is squeezed into adjacent cavities by applied pressure.
Tungsten T H E R E D U C T I O N OF D O P E D T U N G S T E N BLUE O X I D E ( T B O ) TO NON-SAG T U N G S T E N - A L I T E R A T U R E REVIEW
B. Zeiler et al, (Technical University, Vienna, Austria), Int J. Refractory Metals and
Hard Materials, Vol 10 No 2, 1991, 83-90. A review of the literature concerning the doping of TBO with I~ A1 or Si and the s u b s e q u e n t H r e d u c t i o n to metal, was presented. The effects of the p r o p e r t i e s of the blue oxide with respect to doping reactions, the formation of intermediate W o x i d e s a n d ~W a n d t h e r e d u c t i o n of dopants containing compounds on reduction kinetics were discussed. Conclusions on t h e t h e o r i e s of d o p a n t i n c o r p o r a t i o n , a review of r e d u c t i o n p a r a m e t e r s and p o w d e r properties were presented. T H E R E D U C T I O N OF D O P E D T U N G S T E N B L U E O X I D E ( T B O ) TO NON-SAG T U N G S T E N - M E C H A N I S T I C CONSIDERATIONS
B. Zeiler et al, (Technical University, Vienna, Austria), Int J. Refractory Metals a n d
Hard Materials, Vol 10, No 2, 1991, 91105. Experimental observations of the reduction of d o p e d TBO are described. Differences were noted between the sub oxides formed on reduction of d o p e d and u n - d o p e d TBO. A m e c h a n i s m for t h e i n c o r p o r a t i o n of t h e d o p a n t s , chemical vapour transfer and overgrowth phases, in
Cobalt SINTERING CHARACTERISTICS ULTRAFINE COBALT POWDER
OF
Y Sakka, (National I~'esearch inst.ilute for Metals, ,lapan). J. Less Commo'** Metals.
tqd 168, No 2, 1991, 2772,S'7. The s i m e r i n g of u l t r a l i n e ( n powders in vacuunl an(t t[ was nlorlilored hv s t r u c t u r a l a n d d i m e n s i o n a l changes. The p r e s e n c e of i n c l u ( t e d o x i d e s h i n d e r s s i n l e r i n g il, vacuunl but in H t h e o x i d e s are reduced and significant (tensifi(:ation occurs. Gases are evolve(I d u r i n g ~ a c u u m s i n t e r i n g a n d t h e s e were identified as Co e, CO, tie a n d lift). Surface condit;ions are d i s c u s s e d by c o n s i d e r a t i o n of t h e (h~sort)tion sl)ectra.
Copper FACTORS INFLUENCING THE QUALITY OF E L E C T R O I N T I C C O P P E R P O W D E R A. I)urisinova, (Sh)vak A(:a(lemy of Sciences, K(,sice C z e c h o s h ) v a k i a ) , P o w d e r
Metallurgy, Vol 33, No 2, 199l. 139 141. The eflbcts of tint(! of growlh, current d e n s i l y , eleci r o l y t e c o m p o s i t i o n a n d len~l)eralure pll. c i r c u l a l i o n ()I" t h e electrolyte a n d l h e p r e s e n c e of i m p u r i t i e s on the quality of e l e c t r o l ~ i c Cu p o w d e r s have heen stu(lied. C h a n g e s in p o w d e r properties were delermined and the powders were e x a m i n e d microscopically.
Iron a n d S t e e l THE WORKABILITY OF POROUS STEEL PREFORMS A. El I)omialy, M. Shaker. (Suez Canal University, Egypt), ,L Materials Processin.q
Technology, Vol 25, No 2, 1991, 2 2 9 233. A t t e n t i o n is drawn to a m a j o r limitation of powder forging of steel, cracking in t h e (tie. A m e t h o d of c h a r a c l e r i s i n g workability h a s been developed for w r o u g h t m e t a l s a n d applied to p o r o u s metals. Workability limits for s i n t e r e d Fe-0.2%C-0.5%Mo-0.04%S0.04%P w i t h d i f f e r e n t p o r o s i t i e s w e r e d e t e r m i n e d a n d it w a s d e d u c e d t h a t porosity is the m a i n p a r a m e t e r controlling workability of p o r o u s materials.
EFFECT OF SINTERING CONDITIONS ON ISOTHERMAL DECOMPOSITION OF AUTENITE IN SINTERED STEELS V.N. Antsiferov et al, Stal', No 12, 1990, 84-
ferro-alloys are u s e d in p r o d u c t i o n of steels. The p a p e r r e p o r t s on how ferro-alloys influence properties structure and sintering charaeleristics of s i n t e r e d ferrous alloys.
87. In R~ssian. The isothermal decomposition of A u s t e n i t e in PM steels c o m a i n i n g either 1.0 to 1.5%C a n d 3%Cu or" 1.0%C a n d 1.0%Mn was investigated with respect to the s i n t e r i n g a t m o s p h e r e . The s t r u c t u r e s were e x a m i n e d a n d it was l o u n d t h a t on s i n t e r i n g in s t a g n a n t a t m o s p h e r e s a e e m t i t e network w a s f o r m e d a n d t h e r e were g r a p h i t e i n c l u s i o n s w h i c h n u c l e a t e d the b r e a k d o w n of A u s t e n i t e t h i s r e d u c i n g the. i n c u b a t i o n period. It w a s found t h a t t h e C-Cu steel required a double heat treatmenl aud requench quench from 860 C a n d t e m p e r i n g at 300~C to a t t a i n greater s t r e n g t h . EFFECTS OF PRODUCTION PARAMETERS ON STRUCTURE AND PROPERTIES OF REDUCED AND ATOMISED IRON POWDERS 1.P. Argent'seva et al, (Moscow Evening Metallurgical Institute, USSR), Stal', No 11,
1990, 87-92. b~ Ru,ssiar~. The s t r u c t u r e a n d p r o p e r t i e s of r e d u c e d a n d a t o m i s e d Fe powders were investigated. Powder surface morpholog5 ~ a n d O c o n t e n t in relation t.o compactibility are d i s c u s s e d with respecl to t h e f o r m a t i o n of interparticle c o n t a c t s d u r i n g p r e s s i n g a n d s t r e n g t h a n d d e n s i t y of t h e c o m p a c t s . ULTRA HIGH STRENGTH FERROUS COMPONENTS
SINTERED
O. Durukimi et al, (Kawasaki Steel Corporation, Kawasaki, J a p a n ) , D~t J. P o w d e r
Metall,Jrgy, Vol 27, No 4, 1991, 331-337. A newly developed steel c o n t a i n i n g 2%Ni a n d l%Mo with tensile s t r e n g t h 1500 MPa, impact s t r e n g t h 21J, r o t a t i n g b e n d fatigue s t r e n g t h 460 MPa a n d c o m p a c t fatigue s t r e n g t h 2560 MPa is described. It w a s r e p o r t e d t h a t p r o p e r t i e s couM be i n c r e a s e d by double pressing, resintering, h a r d e n i n g a n d tempering. The i n c r e a s e d s t r e n g t h s are a t t r i b u t e d to a s t r a i n i n d u c e d m a r t e n s i t i c t r a n s f o r m a t i o n in t h e r e t a i n e d Austenite.
ENHANCED SINTERING AND PROPERTY IMPROVEMENTS IN SINTERED FERROUS COMPONENTS D.S. Madan, (Elkem D e v e l o p m e n t Centre, Sewiekley, P e n n s y l v a n i a , U S A ) , I n t J.
P o w d e r Metallurgy, Vol 27, No 4, 1991, 339-345. M o d e l s of e n h a n c e d s i n t e r i n g a r e reviewed a n d t h e role of a d d i t i o n s of ferro-alloys to PM steels is discussed. The m e c h a n i c a l a n d p h y s i c a l p r o p e r t i e s of w a t e r a t o m i s e d DFe p o w d e r alloyed with h i g h p u r i t y f e r r o - p h o s p h o r o u s or ferroboron are described. The p r o p e r t i e s are shown to be s u p e r i o r w h e n high p u r i t y
IMPROVED PROPERTIES AND P E R F O R M A N C E O F LOW ALLOY S T E E L PARTS THROUGH HIGH TEMPERATURE SINTERING K. S h i m a d a , (Tokyo Sintered Metals Corporation, Tokyo, .Japan), [nt J. P o w d e r
Metallurgy, Vol 27, No 4, /991, 357-361. S u p e r i o r s t r e n g t h , fatigue p r o p e r t i e s a n d w e a r r e s i s t a n c e are r e p o r t e d to have been a t t a i n e d in low alloy st,eel PM p a r t s by s i n t e r m g at 1250:C, carburising, h a r d e n i n g a n d tempering. The p r o p e r l y i m p r o v e m e n t s a r e a t t r i b u t e d to p o r o s i t y r e d u c t i o n , s p h e r o i d i s a t i o n of r e s i d u a l p o r e s a n d increased neck growth d u r i n g sintering. A u t o m o t i v e a p p l i c a t i o n s a r ( discussed. NEW SINTERED STEELS CONTAINING HARD PHASES FOR WEAR RESISTANT APPLICATIONS F. Thfimmler, C. Gutsfeld. (University ol Karlsruhe, Karlsruhe, G e r m a n y ) , P o w d e r
Metall. Int, Vol 23, No 5, /991, 285-290. T h e p r o d u c t i o n of Fe b a s e d m e t a l m a t r i x c o m p o s i t e s (MMC', c o n t a i n i n g 10 to 30vo>,; of h a r d plrases NbC. TiC of AI~O:~, u s i n g m e c ' h a n i c a l a l l o y i n g (MA) to incorporate the hard phase and sintering at 128()"C in H is d e s c r i b e d The a d d i t i o n of C or P to create a liquid ptmse d u r i n g s i n t e r i n g resulted in d e n s i t i e s of 97 to 99?,; a n d a u n i f o r m d i s t r i b u t i o n of t h e h a r d particles was d u e to t h e ~se of MA. The mechanical properties and wear c h a r a c t e r i s t i c s were, shown to d e m o n s t r a t e t h e p o t e n t i a l of t h e m a t e r i a l s lot u s e in wear resistant applications
PROPERTIES OF WATER ATOMISED IRON POWDER CONTAINING PHOSPHOROUS AND CARBON OR BORON AND SILICON T. Sato et al, J. Materials Science, Vol 26,
No 9, 1991, 2329-2336. The mierostructure and powder p r o p e r t i e s of w a t e r a t o m i s e d Fe-P-C a n d Fe-B-Si a l l o y s w e r e i n v e s t i g a t e d w i t h respect to glass f o r m i n g conditions. The metallic glass p o w d e r s h a d not flowability. It w a s also found t h a t p a r t i c l e s b e c a m e m o r e irregular as t h e size increased. In crystalline powders both ~ and intermetallic p h a s e s were found in hypoa n d hyper-eutectic ;alloys.
STRUCTURAL CHARACTERISTICS ATOMISED WHITE CAST IRON POWDER
OF
A.P. Gulyaev et al, Metalloved. Term. Obrab
Met, No 1, 1991, 34-35. I~ R u s s i a n .
MPR February 1992 57
i~
The structures of atomised white cast iron powders containing 2.5 to 4.5%C and solidified at 10 to 105°C/sec were studied. The structures were very different from those of normal white cast iron. Increased cooling rate reduced the vol fraction of eutectic but at 3.9%C the structure was wholly eutectic. The structure was refined by i n c r e a s e d cooling rate. The r a p i d l y cooled Austenite was s a t u r a t e d with C. E F F E C T S OF H E A T I N G M E T H O D D U R I N G S I N T E R I N G ON S T R U C T U R E A N D P R O P E R T I E S OF IRON-BASE MATERIALS
N.A. Nikishov et al, Metalloved
Term. Obrab. Met, No 1, 1991, 35-37. In Russian.
The structure, p h a s e composition and mechanical p r o p e r t i e s of s i n t e r e d rings made from Fe-l.8%C-2.9%Cr-l.9%Cu or an alloy containing a special Cr carbide in addition to 0.6%C were described. Process conditions are stated. Induction sintering was r e p o r t e d to yield a p r o d u c t of better quality. E F F E C T S OF A D D I T I O N S OF ALKALI METAL C O M P O U N D S O N S T R U C T U R E A N D P R O P E R T I E S OF PM CARBON STEEL
L.N. D'yachkov et al, Metalloved
Term Obrab met, No 1, 1991, 37-39. In Russian.
The addition of bicarbonates of Na, K or Li to a PM steel with 0.5 to 0.55%C was found to accelerate diffusion of C in the steel, increase the a m o u n t of C retained and yield a m o r e h o m o g e n e o u s s t r u c t u r e , particularly at low sintering temperatures. Improved mechanical properties were reported when alkali bicarbonate additions in the range 0.2 to 0.5% were made. Sintering of the compacted powders was in the range 950 to 1250°C for 2 hours. E F F E C T OF S I N T E R I N G C O N D I T I O N S ON T H E M E C H A N I C A L P R O P E R T I E S OF M E T A L I N J E C T I O N M O U L D E D (MIM) STAINLESS STEEL
M. Tsuda, H. Kyogoju, J. J a p a n Soe Powder
and Powder Metallurgy, Vol 38, No 4, 1991, 523-528. In Japanese. The effects of sintering conditions on the density and mechanical properties of MIM 304L s t a i n l e s s steel w e r e investigated. Density was increased by increased time and/or temperature. Specimens were cooled e i t h e r in N or vacuum. The N cooled specimens had higher h a r d n e s s an s t r e n g t h which were a t t r i b u t e d to nitride formation at the surface. E F F E C T S OF B O R I D E A D D I T I O N S ON S I N T E R I N G OF A U S T E N T I T I C STAINLESS STEEL POWDER COMPACTS M. Kamada et al, J. J a p a n Soc Powder and
Powder Metallurgy, Vol 38, NO 2, 1991, 529-534. In Japanese. 58
MPR
February
1992
PMLITERATURE
REVIEW
The effects of b o r i d e a d d i t i o n s on d e n s i f i c a t i o n o f 304L s t a i n l e s s s t e e l powder were studies with respect to liquid p h a s e sintering. CrB t r a n s f o r m s the Cr3B d u r i n g s i n t e r i n g a n d a e u t e c t i c liquid between this and the m a t r i x p h a s e forms. Small pores were found to d i s a p p e a r but large ones remained and t h e s e were said to be located at the site of the original CrB particles. The liquid p h a s e is r e p o r t e d to aid in densification and solidifies to Cr2B plus Austenite. Similar results are reported for FeB and NiB additions. E F F E C T S OF CARBON C O N T E N T O N S I N T E R I N G BEHAVIOUR A N D T E N S I L E P R O P E R T I E S OF S I N T E R E D MARTENSITIC STAINLESS STEELS
M. Kamada, Y. Tokunaga, J. J a p a n
Soc Powder and Powder Metallurgy, Vol 38, No 2, 1991, 535-539. In Japanese. The effects of carbon content, sintering t e m p e r a t u r e and heat t r e a t m e n t conditions on the p r o p e r t i e s on sintered martensitic 410L stainless steel were investigated. It was reported t h a t the vol fraction of ferrite at the s i n t e r i n g t e m p e r a t u r e d e c r e a s e s w i t h i n c r e a s e in %C a n d decrease in sintering temperature, aferrite is said to aid d e n s i f i c a t i o n a n d p o r e r o u n d i n g due to high self diffusion. A m i n i m u m of 0.1%C is required to produce a martensitic structure. Strength increases with %C due to e n h a n c e d densiflcation.
Molybdenum B O R O N I S I N G T R E A T M E N T FOR SINTERED MOLYBDENUM-NICKEL POWDER COMPACTS
T. Sakamoto. J. J a p a n Soe Powder and
Powder Metallurgy, Vol 38, No 4, 1991, 492-498. In Japanese. Boronising using BoB, NiB and B4C in an a c t i v a t o r c o n t a i n i n g NH4C1, BaF3 or Na2CO3, of sintered Mo and Mo-38% was investigated. The b o r o n i s e d alloys were e x a m i n e d by X-ray diffraction and electron probe micro analysis (EPMA). It was found t h a t the thickness of the boronised layers increased with time a n d / o r temperature. The layers c o n t a i n e d MoB, Mo2B a n d Mo2B5. The c h l o r i d e or f l u o r i d e w e r e identified w h e n p r e s e n t in the activator. NiB powder was not found to increase the boride layer thickness.
Titanium P R O D U C T I O N OF T I T A N I U M BASE M E T A L MATRIX C O M P O S I T E S ( M M C ) BY VACUUM PLASMA SPRAYING
P.A. Dearnley, K.A. Roberts, (University of Cambridge, Cambridge, England), Powder Metallurgy, Vol 34, No 2, 1991, 112-118.
~
The p r o d u c t i o n of Ti-base MMC by vacuum p l a s m a spraying has been studied by high s p e e d cinematography. The p l a s m a was found to show fluctuations in length. The m e c h a n i s m of co-spray deposition has been elucidated by use of a wipe test and is d e s c r i b e d as e m b e d d i n g of c e r a m i c p a r t i c l e s into t h e s u b s t r a t e f o l l o w e d by covering w i t h Ti splats. M e t a l / c e r a m i c collisions in flight are r e p o r t e d to be of small significance. MICROSTRUCTURE AND MECHANICAL P R O P E R T I E S OF R E S I S T A N C E SINTERED TITANIUM
C.H. Lui, P.W. Kao, Scripta MetaU Mater,
Vol 24 No 12, 1990, 2279-2284. An i n v e s t i g a t i o n into t h e r e s i s t a n c e s i n t e r i n g o f Ti, w h i c h s h o w e d r a p i d d e n s i f i c a t i o n to d e n s i t y above 96% in a b o u t 2 s e c o n d s , is d e s c r i b e d . T h e r e s i s t a n c e s i n t e r e d Ti was r e p o r t e d to have higher s t r e n g t h t h a n conventional PM Ti. T h e r a p i d d e n s i f i c a t i o n is attributed to the formation of a liquid p h a s e at p a r t i c l e b o u n d a r i e s w h i c h is squeezed into adjacent cavities by applied pressure.
Tungsten T H E R E D U C T I O N OF D O P E D T U N G S T E N BLUE O X I D E ( T B O ) TO NON-SAG T U N G S T E N - A L I T E R A T U R E REVIEW
B. Zeiler et al, (Technical University, Vienna, Austria), Int J. Refractory Metals and
Hard Materials, Vol 10 No 2, 1991, 83-90. A review of the literature concerning the doping of TBO with I~ A1 or Si and the s u b s e q u e n t H r e d u c t i o n to metal, was presented. The effects of the p r o p e r t i e s of the blue oxide with respect to doping reactions, the formation of intermediate W o x i d e s a n d ~W a n d t h e r e d u c t i o n of dopants containing compounds on reduction kinetics were discussed. Conclusions on t h e t h e o r i e s of d o p a n t i n c o r p o r a t i o n , a review of r e d u c t i o n p a r a m e t e r s and p o w d e r properties were presented. T H E R E D U C T I O N OF D O P E D T U N G S T E N B L U E O X I D E ( T B O ) TO NON-SAG T U N G S T E N - M E C H A N I S T I C CONSIDERATIONS
B. Zeiler et al, (Technical University, Vienna, Austria), Int J. Refractory Metals a n d
Hard Materials, Vol 10, No 2, 1991, 91105. Experimental observations of the reduction of d o p e d TBO are described. Differences were noted between the sub oxides formed on reduction of d o p e d and u n - d o p e d TBO. A m e c h a n i s m for t h e i n c o r p o r a t i o n of t h e d o p a n t s , chemical vapour transfer and overgrowth phases, in