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Improved forgeability and properties of titanium aluminide by use of PM
PM
A r a n g e of PM steels c o n t a i n i n g Cu or Mo or with Ni, Cu a n d Mo were carburized using plasma, gaseous or v a c u u m m e t h o d s a n d h a r d e n e d by oil q u e n c h i n g . T h e s a m p l e s were c h a r a c t e r i z e d by o p t i c a l microscopy, X-ray analysis and microhardness and wear and fatigue properties were determined. ION A N D GAS N I T R I D I N G OF H O M O G E N E O U S S I N T E R E D ALLOY STEELS G.F. Bocchini et al (HSganSs Italia, Genoa, Italy). An investigation of ion a n d gas nitriding of low alloy, 1.5%Mo, a n d high alloy, 316L a n d 410L, stainless steels was described. Densities varied in t h e range 6.4 to 7.5 g/ cm 3. I n t e r c o n n e c t e d porosity was shown to allow deep p e n e t r a t i o n of N in gas nitriding causing swelling and embrittlement. Swelling was not detected with ion nitriding. The alloy e l e m e n t s were shown to have similar effects to t h o s e found in w r o u g h t steels. It was suggested t h a t gas nitriding of PM steel should be restricted to those with only closed porosity or very high density.
High temperature materials TUNGSTEN-MOLYBDENUM-COPPER ALLOYS X. Gui-Lan (Central Iron a n d Steel Research Inst, Beijing, China). Application of W-Mo-Cu alloys in rocket m o t o r s was discussed with regard to service conditions, high temperatures, rapid h e a t i n g a n d cooling a n d t h e n e e d to w i t h s t a n d a b l a t i o n . The W-Mo-Cu alloy was shown to w i t h s t a n d t h e s e conditions. D E V E L O P M E N T O F A HIP PM SUPERALLOY W. Y a n g e t al ( I n s t of A e r o n a u t i c a l Materials, Beijing, China). Defects, in p a r t i c u l a r precipitation at prior particle b o u n d a r i e s (PPPB), in PM superalloys were reviewed. A novel p o w d e r h e a t t r e a t m e n t to m i n i m i z e PPPB, by reduction of segregation a n d alteration of p r e c i p i t a t e s o n p a r t i c l e surfaces, was described. It was r e p o r t e d t h a t t h e r e were i m p r o v e m e n t s in p r o p e r t i e s a n d t h e materials were more reliable. LIQUID P H A S E S I N T E R I N G OF HARD AND WEAR R E S I S T A N T SATELLITES M. H a m i u d d i n (Regional College of Engineering a n d Technology, Aligarh, India). It was r e p o r t e d t h a t satellites of various c o m p o s i t i o n w i t h h a r d n e s s 47 t o 61 Rockwell C h a d been p r o d u c e d from gas atomized stellite 6 powders. The alloys were liquid p h a s e s i n t e r e d a t 1100 to 1200°C in v a c u u m or H. Sintering t e m p e r a t u r e could be reduced by increased a d d i t i o n s of B a n d increase in %C a n d %W improved sintered density a n d h a r d n e s s b u t reduced s t r e n g t h
LITERATURE
REVIEW
and toughness. Some compositions sintered to near full density. A STUDY OF OXIDATION R E S I S T A N T S I N T E R E D IRON-CHROMIUMALUMINIUM HONEYCOMBE STRUCTURE T. O h a s h i et al (NGK I n s u l a t o r s Ltd, Nagoya, J a p a n ) . The application of Fe-Cr-A1 alloys in automotive catalytic converters was d i s c u s s e d a n d it was n o t e d t h a t t h e rollability of these alloys into t h i n foils was limited by t h e A1 content. Honeycombe s t r u c t u r e s were produced from Fe-(12 to 20)wt%Cr-(5 to 10)%A1 powders mixed w i t h a n o r g a n i c b i n d e r by e x t r u s i o n , d e b i n d i n g a n d sintering. High resistance to o x i d a t i o n was reported a n d it was shown t h a t F e - ( 1 2 to 16)%Cr-10%AI h a d t h e lowest weight gain of 0.5 m g / c m 2 after isothermal heating in air at 1150°C for 100 hours. DUAL P R O P E R T I E S BY HIP OF A NICKEL BASE SUPERALLOY M.C. Somani et al (Defence Metallurgical Research Laboratory, Hyderabad, India). The use of HIP to obtain dual properties in a Ni base superalloy IN100 by combining cast a n d wrought properties was described. HIP was r e p o r t e d to be used to consolidate powder a n d h e a t casting defects in a single o p e r a t i o n where a powder was used to p r o d u c e a s i n t e r e d surface layer on a casting. Good diffusion bonding was reported in an interface layer 50 to 60 pm thick. Structure and properties were described. SYNTHESIS OF TITANIUM ALUMINIDETITANIUM BORIDE C O M P O S I T E S BY C O M B U S T I O N REACTION X. Qu et al (Central South University of Technology, Changsha, Hunan, China). It was reported t h a t a TiA1 material reinforced with TiB2 h a d been p r o d u c e d by reaction synthesis from elemental Ti, AI a n d B powders. TiAl a n d TiB2 were formed a n d t h e TiB~ particles were shown to be a b o u t 2 lam in size. The grain size of t h e TiA1 m a t r i x was finer t h a n t h a t of t h e cast of the same composition. PM P R O C E S S I N G TO PRODUCE O R D E R E D TITANIUM ALUMINIDE BASE ALLOYS X. Qu et al (Central South University of Technology, Changsha, Hunan, China), Ti-48 a t %A1-2%Cr-2%Nb alloys were p r o d u c e d from mechanically c o m m i n u t e d Ti-54%A1-2.25%Cr-2.25%Nb p o w d e r s a n d e l e m e n t a l Ti p o w d e r by p r e c o m p a c t i o n a n d HIP followed by h e a t t r e a t m e n t to obtain high density and chemical homogeneity. The m e c h a n i c a l p r o p e r t i e s were discussed with reference to process parameters.
IMPROVED FORGEABILITY AND P R O P E R T I E S OF TITANIUM ALUMINIDE BY USE OF PM D. Eylon et al ( U n i v e r s i t y of Dayton, Dayton, Ohio, USA). The mechanical properties and m i c r o s t r u c t u r e of Ti-48at%A1-2%Nb-2%Cr, which h a d been HIPed a t 1000°C a n d 200 MPa from gas a t o m i z e d prealloyed powder, were investigated. Ambient t e m p e r a t u r e s t r e n g t h s of 550 MPa with 2% elongation were reported. The alloys were hot forged in close dies at 1175°C a n d s t r a i n rates of 0.1 min-1. Heat t r e a t m e n t at 1180 or 1290°C resulted in coarsening of the structure and reduced strength, ductility a n d forgeability. USE OF THE CERACONT M P S E U D O - H I P P R O C E S S TO CONSOLIDATE ZIRCONIUM ALUMINIDE R.V. R a m a n et al (Ceracon Inc, Sacramento, California, USA). The use of t h e Ceracon process for c o n s o l i d a t i o n of s t o i c h i o m e t r i c Zr3A1 powders was described. Densification was said to be rapid a n d oxidation a n d reverse peritectoid reactions were prevented yielding a p u r e intermetallic compound. A p p l i c a t i o n s were d i s c u s s e d a n d d a t a concerning microstructures a n d oxidation kinetics were presented. P R O D U C T I O N OF NIOBIUM ALUMINIDE BY PLASMA-MELT-GASATOMIZATION N. M u r a h a s h i et al (Mitsubishi Metals Corp, Nagata, J a p a n ) . It was reported t h a t plasma-melt-gasa t o m i z a t i o n h a d been u s e d to p r e p a r e rapidly solidified powders of intermetallic compounds and the equipment was described. The m e t h o d was a p p l i e d to Nb3Al. The s t r u c t u r e s of t h e powders were shown to be a s u p e r s a t u r a t e d solid solution of A1 in Nb of a n d ordered A15 NbaAl. SOLID STATE SYNTHESIS OF INTERMETALLICS BY COLD S I N T E R I N G OF E L E M E N T A L POWDERS E.Y. G u t m a n a s et al (Technion, Haifa, Israel). A range of intermetallic c o m p o u n d s of Co-A1, Ni-Al, Fe-Ti, Ni-Ti, Co-Ti a n d Co-W were synthesized by very high p r e s s u r e consolidation or cold sintering followed by thermal treatment using elemental powders. Effects of process p a r a m e t e r s on s t r u c t u r e a n d properties were investigated. It was shown t h a t t h e m e t h o d was capable of making n e a r net s h a p e parts. A D H E S I O N S T R E N G T H BETWEEN DIAMOND FILM A N D C E M E N T E D CARBIDE S U B S T R A T E S N. Omori, M. Kobayashi ( S u m i t o m o Electric
MPR April 1994 53
A r a n g e of PM steels c o n t a i n i n g Cu or Mo or with Ni, Cu a n d Mo were carburized using plasma, gaseous or v a c u u m m e t h o d s a n d h a r d e n e d by oil q u e n c h i n g . T h e s a m p l e s were c h a r a c t e r i z e d by o p t i c a l microscopy, X-ray analysis and microhardness and wear and fatigue properties were determined. ION A N D GAS N I T R I D I N G OF H O M O G E N E O U S S I N T E R E D ALLOY STEELS G.F. Bocchini et al (HSganSs Italia, Genoa, Italy). An investigation of ion a n d gas nitriding of low alloy, 1.5%Mo, a n d high alloy, 316L a n d 410L, stainless steels was described. Densities varied in t h e range 6.4 to 7.5 g/ cm 3. I n t e r c o n n e c t e d porosity was shown to allow deep p e n e t r a t i o n of N in gas nitriding causing swelling and embrittlement. Swelling was not detected with ion nitriding. The alloy e l e m e n t s were shown to have similar effects to t h o s e found in w r o u g h t steels. It was suggested t h a t gas nitriding of PM steel should be restricted to those with only closed porosity or very high density.
High temperature materials TUNGSTEN-MOLYBDENUM-COPPER ALLOYS X. Gui-Lan (Central Iron a n d Steel Research Inst, Beijing, China). Application of W-Mo-Cu alloys in rocket m o t o r s was discussed with regard to service conditions, high temperatures, rapid h e a t i n g a n d cooling a n d t h e n e e d to w i t h s t a n d a b l a t i o n . The W-Mo-Cu alloy was shown to w i t h s t a n d t h e s e conditions. D E V E L O P M E N T O F A HIP PM SUPERALLOY W. Y a n g e t al ( I n s t of A e r o n a u t i c a l Materials, Beijing, China). Defects, in p a r t i c u l a r precipitation at prior particle b o u n d a r i e s (PPPB), in PM superalloys were reviewed. A novel p o w d e r h e a t t r e a t m e n t to m i n i m i z e PPPB, by reduction of segregation a n d alteration of p r e c i p i t a t e s o n p a r t i c l e surfaces, was described. It was r e p o r t e d t h a t t h e r e were i m p r o v e m e n t s in p r o p e r t i e s a n d t h e materials were more reliable. LIQUID P H A S E S I N T E R I N G OF HARD AND WEAR R E S I S T A N T SATELLITES M. H a m i u d d i n (Regional College of Engineering a n d Technology, Aligarh, India). It was r e p o r t e d t h a t satellites of various c o m p o s i t i o n w i t h h a r d n e s s 47 t o 61 Rockwell C h a d been p r o d u c e d from gas atomized stellite 6 powders. The alloys were liquid p h a s e s i n t e r e d a t 1100 to 1200°C in v a c u u m or H. Sintering t e m p e r a t u r e could be reduced by increased a d d i t i o n s of B a n d increase in %C a n d %W improved sintered density a n d h a r d n e s s b u t reduced s t r e n g t h
LITERATURE
REVIEW
and toughness. Some compositions sintered to near full density. A STUDY OF OXIDATION R E S I S T A N T S I N T E R E D IRON-CHROMIUMALUMINIUM HONEYCOMBE STRUCTURE T. O h a s h i et al (NGK I n s u l a t o r s Ltd, Nagoya, J a p a n ) . The application of Fe-Cr-A1 alloys in automotive catalytic converters was d i s c u s s e d a n d it was n o t e d t h a t t h e rollability of these alloys into t h i n foils was limited by t h e A1 content. Honeycombe s t r u c t u r e s were produced from Fe-(12 to 20)wt%Cr-(5 to 10)%A1 powders mixed w i t h a n o r g a n i c b i n d e r by e x t r u s i o n , d e b i n d i n g a n d sintering. High resistance to o x i d a t i o n was reported a n d it was shown t h a t F e - ( 1 2 to 16)%Cr-10%AI h a d t h e lowest weight gain of 0.5 m g / c m 2 after isothermal heating in air at 1150°C for 100 hours. DUAL P R O P E R T I E S BY HIP OF A NICKEL BASE SUPERALLOY M.C. Somani et al (Defence Metallurgical Research Laboratory, Hyderabad, India). The use of HIP to obtain dual properties in a Ni base superalloy IN100 by combining cast a n d wrought properties was described. HIP was r e p o r t e d to be used to consolidate powder a n d h e a t casting defects in a single o p e r a t i o n where a powder was used to p r o d u c e a s i n t e r e d surface layer on a casting. Good diffusion bonding was reported in an interface layer 50 to 60 pm thick. Structure and properties were described. SYNTHESIS OF TITANIUM ALUMINIDETITANIUM BORIDE C O M P O S I T E S BY C O M B U S T I O N REACTION X. Qu et al (Central South University of Technology, Changsha, Hunan, China). It was reported t h a t a TiA1 material reinforced with TiB2 h a d been p r o d u c e d by reaction synthesis from elemental Ti, AI a n d B powders. TiAl a n d TiB2 were formed a n d t h e TiB~ particles were shown to be a b o u t 2 lam in size. The grain size of t h e TiA1 m a t r i x was finer t h a n t h a t of t h e cast of the same composition. PM P R O C E S S I N G TO PRODUCE O R D E R E D TITANIUM ALUMINIDE BASE ALLOYS X. Qu et al (Central South University of Technology, Changsha, Hunan, China), Ti-48 a t %A1-2%Cr-2%Nb alloys were p r o d u c e d from mechanically c o m m i n u t e d Ti-54%A1-2.25%Cr-2.25%Nb p o w d e r s a n d e l e m e n t a l Ti p o w d e r by p r e c o m p a c t i o n a n d HIP followed by h e a t t r e a t m e n t to obtain high density and chemical homogeneity. The m e c h a n i c a l p r o p e r t i e s were discussed with reference to process parameters.
IMPROVED FORGEABILITY AND P R O P E R T I E S OF TITANIUM ALUMINIDE BY USE OF PM D. Eylon et al ( U n i v e r s i t y of Dayton, Dayton, Ohio, USA). The mechanical properties and m i c r o s t r u c t u r e of Ti-48at%A1-2%Nb-2%Cr, which h a d been HIPed a t 1000°C a n d 200 MPa from gas a t o m i z e d prealloyed powder, were investigated. Ambient t e m p e r a t u r e s t r e n g t h s of 550 MPa with 2% elongation were reported. The alloys were hot forged in close dies at 1175°C a n d s t r a i n rates of 0.1 min-1. Heat t r e a t m e n t at 1180 or 1290°C resulted in coarsening of the structure and reduced strength, ductility a n d forgeability. USE OF THE CERACONT M P S E U D O - H I P P R O C E S S TO CONSOLIDATE ZIRCONIUM ALUMINIDE R.V. R a m a n et al (Ceracon Inc, Sacramento, California, USA). The use of t h e Ceracon process for c o n s o l i d a t i o n of s t o i c h i o m e t r i c Zr3A1 powders was described. Densification was said to be rapid a n d oxidation a n d reverse peritectoid reactions were prevented yielding a p u r e intermetallic compound. A p p l i c a t i o n s were d i s c u s s e d a n d d a t a concerning microstructures a n d oxidation kinetics were presented. P R O D U C T I O N OF NIOBIUM ALUMINIDE BY PLASMA-MELT-GASATOMIZATION N. M u r a h a s h i et al (Mitsubishi Metals Corp, Nagata, J a p a n ) . It was reported t h a t plasma-melt-gasa t o m i z a t i o n h a d been u s e d to p r e p a r e rapidly solidified powders of intermetallic compounds and the equipment was described. The m e t h o d was a p p l i e d to Nb3Al. The s t r u c t u r e s of t h e powders were shown to be a s u p e r s a t u r a t e d solid solution of A1 in Nb of a n d ordered A15 NbaAl. SOLID STATE SYNTHESIS OF INTERMETALLICS BY COLD S I N T E R I N G OF E L E M E N T A L POWDERS E.Y. G u t m a n a s et al (Technion, Haifa, Israel). A range of intermetallic c o m p o u n d s of Co-A1, Ni-Al, Fe-Ti, Ni-Ti, Co-Ti a n d Co-W were synthesized by very high p r e s s u r e consolidation or cold sintering followed by thermal treatment using elemental powders. Effects of process p a r a m e t e r s on s t r u c t u r e a n d properties were investigated. It was shown t h a t t h e m e t h o d was capable of making n e a r net s h a p e parts. A D H E S I O N S T R E N G T H BETWEEN DIAMOND FILM A N D C E M E N T E D CARBIDE S U B S T R A T E S N. Omori, M. Kobayashi ( S u m i t o m o Electric
MPR April 1994 53