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Characterization of liquid breakup mechanisms for atomization nozzles
Development of a device, sensitive to the various species evolved was reported together with a description of its use in the control of debinding. The principles of the device were outlined. The cost was shown to be low and the technique was considered to have potential for control of industrial debinding of MIM parts. SOLVENT DEBINDING OF INJECTION MOULDED PARTS WITH SUPERCRITICAL CARBON DIOXIDE T. Shimizu et al. (Uthonomiya University, Japan.) The use of liquid COs, under high pressures, as a debinding solvent, was reported. The liquid dissolves wax selectively. A part, 5 mm in thickness, was reported to have been debound in less than 1 hour. The potential of the method was discussed. METAL INJECTION MOULDING OF INVAR SYN’. NILVAR ABose. (Parmatech Corp, Petaluma, California, USA) Ni-Fe alloys were reviewed with reference to low thermal expansion in some alloys and applications of these, notably Invar. The feasibility of using MIM to make parts in these alloys was discussed. Preliminary investigations of Invar were described. MECHANICAL AND THERMAL PROPERTIES OF INJECTION MOULDED ALUMINA CERAMICS M.Youseffi, IAMenzies. (University of Technology, Loughborough, UX.) The mechanical and thermal properties of injection moulded 88%, 95% and 99.5% pure AlsOs were investigated. Two different binder systems were used. It was reported that the propekes were similar to those of pressed and sintered specimens. CORRELATION OF SMALL PUNCH TESTS WITH TENSILE TESTS ON IRONALUMINIUM-SILICON B.LLograsso et al (Ames Laboratory, USA) Measurement of mechanical properties of injection moulded parts was discussed with regard to difficulties imposed by small sizes and complex shapes. An investigation to establish a relationship between tensile tests and small punch tests for a range of Fe base alloys was described. A relationship was established between the results for a biaxial punch test, tensile tests and structure and to provide and alternative to tensile testing. COMPOSITE PARTS BY INJECTION MOULDING R.M.German et al. (Pennsylvania University, Pennsylvania, USA)
State
Combination of different materials in a single part was discussed. An investigation to produce a bi-metallic parts by metal injection moulding was described. problems of adjusting process parameters for a tool steel and a Ni-steel were outlined. Dilatometry studies were used to establish process conditions. A sample part was discussed. SINTERING CHARACTERISTICS OF INJECTION MOULDED STAINLESS STEEL N.H.Loh, X.I.Khar. (Nanyang Technical University, Singapore.) Advantages of the use of MIM to make parts were discussed. An investigation of the sintering of a 316L stainless steel, heated at 5 to 15”C/min to 1050 to 1350°C for 1 to 2 hours, was described. Properties were measured. Maximum shrinkage was 16.5%, maximum density was 98.4%. Most shrinkage occurred at 1050 to 1200°C. Sinterlng was reported to be enhanced by slow heating and maximum temperature. 1.4% open porosity was measured.
Sintering controls PREDICTION OF PART TEMPERATURE PROFILE DURING SINTERING UNDERF PRODUCTION CONDITIONS J.Dwyer et al. (BOC Group Technical Centre, USA) Part temperature and thermal profile during sintering were reviewed with regard to effects. The need to know optimum values for a given part as influenced by belt speed in continuous furnaces and temperature were noted. A PC based model, which predicts part temperature as a function of part characteristics and process conditions was described. The controlling thermal balance equation and use of the model in production conditions were described. Predictions were verified experimentally. Applications were discussed. A COST-EFFECTIVE PREVENTIVE MAINTAINANCE PROGRAMME FOR SINTERING FURNACES G.M.Mayer, T.M.Cadle. (Zenith Sintered Products, Inc., Germantown, USA) It was reported that a preventive maintainance process had been developed for avoidance of interuption to production and prevention of production of out-ofcompliance parts. Emphasis was placed on repair-not-replacement. The technique is designed to supplement existing methods which, while reliable, require expensive equipment and are time consuming. The new methods and shown to, be easily adopted and reliable. An instrument to measure gas flow rates was repoked to aid in monitoring of sinterhardening.
REMOTE ELECTRONIC MANAGEMENT OF SINTERING FURNACES J.Dwyer et al. (BOC Group Technical Centre, USA) A PC based system for monitoring and storage of data concerning factors which control sintering furnaces was described. The system provides access to historical and real time furnace data through a model. The software is shown to be capable of linking hot-spots to sensor locations on furnace diagrams.
A tomb
tion
PRODUCTION OF FINE PREALLOYED POWDERS FOR MIM BY ‘NANOVEL’ GAS ATOMIZATION PROCESS GSchulz. (Nanoval AG, Germany.) Factors which limit the production of fine powders for MIM were identified and discussed. It was reported that the NANOVEL gas atomization process produced powder which did not require screening for MIM and used 33% of the gas needed for conventional atomization. PREDICTIVE COMPUTATIONAL FLUID DYNAMICS OF CLOSE COUPLED ATOMIZARION DIE R.Makineau, R.A.Berry. (Idaho National Engineering Laboratory, USA) The paper described a predictive 2 dimensional axisymmetric computational fluid dynamics model of close coupled gas atomization. The simulation was carried out for Ar and N atomization of a Ni base alloy and used to optimize for minimal gas consumption and maximum powder yield. Predicted and experimental results were compared. A NOVEL GAS ATOMIZATION NOZZLE FOR LIQUID METAL ATOMIZATION I.E.Anderson et al. (Ames Laboratory, USA.) A novel nozzle for close coupled high pressure gas atomization was described. It was reported that a high yield of fine powder was produced. A comparison was made with other processes in respect of gas flow, gas and metal consumption ratios and powder particle size distribution. The resunlts were discussed. CHARACTERIZATION OF LIQUID BREAKUP MECHANISMS FOR ATOMIZATION NOZZLES S.P.Mates, G.S.Settles. (Pennsylvania State University, Pennsylvania, USA) It was reported that several gas atomization nozzles had been characterized using flow visualization techniques with respect to primary disintegration of the metal stream. For each nozzle two mechanisms were MPR March 1997
41
identiEed. Some liquid is forced to the edge of the nozzle and is broken up by the gas flow. The remainder is less energetically disintegrated in the low speed wake. It was suggested that this may explain the wide particle size distribution found in some atomized powders.
High performance
materials
OPTIMIZATION OF SINTERING PARAMETERS FOR HIGH STRENGTH LOW ALLOY STEELS R.M. German et al. (Pennsylvania State University, Pennsylvania, USA) A study of processing Fe alloyed with Cu, Ni, MO and C was undertaken with the object of optimizing process conditions for enhanced properties at densities of about 7.1 gm.cm-‘. The need for identification of key parameters was emphasized and a variable search method was used to this end. These parameters were closely controlled and tolerances in others were broadened in order to reduce costs without loss in final properties SYNERGIES OF HIGH TEMPERATURE SINTERING AND ALLOY DEVELOPMENT FOR PM POWERTRAIN PARTS R.Shivanath, P.K.Jones. (Stackpole Ltd, Oakville, Canada.) High temperature sinterlng of parts was reviewed with reference to costs, properties and dimensional changes. The trend away from high temperature sir&ring was noted. It was argued that an advantage of high temperature sinterlng, alloying freedom, had been overlooked and that good alloying, together with good densification, was critically important. High temperature sintering was considered to be an important factor in the drive to replace steel parts with PM components. The Fe-Mn-C system was described. This system was reported to been used in a range of highly stressed automotive parts. DEVELOPMENT OF HIGH STRENGTH STEELS BY NBW ALLOYING AND SINTERJNG TECBNIQIJES E.Emst et al. (Sintermetallwerk Krebsoge GmbH, Radevormwald, Germany.) The need to avoid the use of free Ni, for environmental reasons, was noted. The elimination of free Ni powder from PM by use of prealloyed powders was discussed with reference to material properties. Alloying of a range of steel powders with Ni was investigated as a function of mechanical and fatigue The studies were properties. finalized with the production of an automotive part.
42 MPR March 1997
Warm compaction EFFECTS OF REPRESSING ON PROPERTIES OF WABM COMPACTED MATERIALS SYSTEMS S.R.Sun, K.R.Crouchman. (Pennsylvania Pressed Metals Inc., USA) Static and dynamic mechanical properties of warm compacted doublepressed/double sintered materials were discussed. Experiments intended to attain steel densities in excess of 7.55 gm.cmm3 were described.
Novel materials SCANDIUM OXYCARBIDE A NOVEL COMPONENT FOR BARD MATERIALS GRoiss et al. (Technical University, Vienna, Austria.) Scandium oxycarbide, Scz (0,C) , the carbide and oxide were discussed with reference to possible use as a constituent of hardmetals. It is noted that the existence of Scz(O,C) has been disputed but it is reported that the hardness of ‘DC is increased from 31 to over 50 GPa by small additions of Scz(O,C). It is suggested that the compound has a wide range of composition with a cubic structure and that Sc(O,N,C) could improve wear resistance of cemented carbides. ALUMINJUM NITRIDE-TUNGSTEN COMPOSITIONALLY GRADED MATERIAL FOR THERMAL BARRIER USE R.Watanabe et al. (Tohoku University, Sendai, Japan.) It was reported that an AlN/W compositionally graded material had been fabricated, layer-by-layer, from 1.39 pm AlN and 5.3 pm W powders, by HIP to full density at 200 MPa and 1850°C. Testing for thermal shock damage was monitored by accoustic emission techniques. The material was shown to have good thermal shock resistance and heat shield properties. STRUCTURAL EVOLUTION DURING SINTERING AND DIFFUSION OF COMPOSITIONALLY GRADED MATERIALS S.C.Yang. (Mando Machinery Corporation, Korea.) It was suggested that compositionally graded Fe/WC-Co materials could be used for wear resistant parts. Specimens were made by pressing and sintering and characterized for microstructure. The material was shown to have good potential for cost effective parts.
CORRELATIONS BETWEEN ISOSTATIC PRESS PARAMETERS AND CHARACTERISTICS OF CERAMIC PARTS C.S.Dumitrn, S,Sever. (University of Craiova, Romania.) Researches into production of parts from transluscent polycrystalline A120s, with respect to correlations between automatic isostatic pressing parameters and characteristics of pressed parts, were described. Optimum process conditions were established and outlined.
Refractory metal composites EFFECT OF COPPER PARTICLE SIZE ON SINTERING OF METAL INJECTION MOULDED TUNGSTEN-COPPER I.H.Moon et al. (Hanyang University, Korea.) The effect of Cu powder particle size on sintering of MIM W-Cu parts was investigated. Milled and mixed powders were compared. A range of Cu powders was used and simntering was evaluated in terms of Cu powder characteristics. The best sintering was attained with fine Cu powder giving densities in excess of 98%. THERMOMECHANICAL PROCESSING OF SINTERED TUNGSTEN-COPPER COMPOSITES EKOhrlner, B.Bryskin. (Oak Ridge National Laboratory, USA.) Properties of W-Cu alloys were discussed with respect to the need for high density and a structure comprising a continuous Cu matrix with W particles. Methods to attain this state, liqiud phase sintering, iniiltration, and these in combination, HIP and MIM, were outlined and it was noted that these do not always reach high density. Thermomechanical processing, to make W4O%Cu with high density, was investigated with regard to structural evolution. It was reported that hot extrusion gave material with high density.
Dimensional OM parts
control of
EFFECT OF SINTERING ON VARIATIONS IN PART DIMENSIONS AVavan et al. (Laval University, Canada) Literature on dimensional control of PM parts was reviewed, A statistical study, in a production environment, of the effects of green density, material and sintering parameters on dimensional variation in parts was described after which alterations were made to process conditions with a further evaluation. It was reported that the procedure could result in the attainment of closer dimensional tolerances.
State
Combination of different materials in a single part was discussed. An investigation to produce a bi-metallic parts by metal injection moulding was described. problems of adjusting process parameters for a tool steel and a Ni-steel were outlined. Dilatometry studies were used to establish process conditions. A sample part was discussed. SINTERING CHARACTERISTICS OF INJECTION MOULDED STAINLESS STEEL N.H.Loh, X.I.Khar. (Nanyang Technical University, Singapore.) Advantages of the use of MIM to make parts were discussed. An investigation of the sintering of a 316L stainless steel, heated at 5 to 15”C/min to 1050 to 1350°C for 1 to 2 hours, was described. Properties were measured. Maximum shrinkage was 16.5%, maximum density was 98.4%. Most shrinkage occurred at 1050 to 1200°C. Sinterlng was reported to be enhanced by slow heating and maximum temperature. 1.4% open porosity was measured.
Sintering controls PREDICTION OF PART TEMPERATURE PROFILE DURING SINTERING UNDERF PRODUCTION CONDITIONS J.Dwyer et al. (BOC Group Technical Centre, USA) Part temperature and thermal profile during sintering were reviewed with regard to effects. The need to know optimum values for a given part as influenced by belt speed in continuous furnaces and temperature were noted. A PC based model, which predicts part temperature as a function of part characteristics and process conditions was described. The controlling thermal balance equation and use of the model in production conditions were described. Predictions were verified experimentally. Applications were discussed. A COST-EFFECTIVE PREVENTIVE MAINTAINANCE PROGRAMME FOR SINTERING FURNACES G.M.Mayer, T.M.Cadle. (Zenith Sintered Products, Inc., Germantown, USA) It was reported that a preventive maintainance process had been developed for avoidance of interuption to production and prevention of production of out-ofcompliance parts. Emphasis was placed on repair-not-replacement. The technique is designed to supplement existing methods which, while reliable, require expensive equipment and are time consuming. The new methods and shown to, be easily adopted and reliable. An instrument to measure gas flow rates was repoked to aid in monitoring of sinterhardening.
REMOTE ELECTRONIC MANAGEMENT OF SINTERING FURNACES J.Dwyer et al. (BOC Group Technical Centre, USA) A PC based system for monitoring and storage of data concerning factors which control sintering furnaces was described. The system provides access to historical and real time furnace data through a model. The software is shown to be capable of linking hot-spots to sensor locations on furnace diagrams.
A tomb
tion
PRODUCTION OF FINE PREALLOYED POWDERS FOR MIM BY ‘NANOVEL’ GAS ATOMIZATION PROCESS GSchulz. (Nanoval AG, Germany.) Factors which limit the production of fine powders for MIM were identified and discussed. It was reported that the NANOVEL gas atomization process produced powder which did not require screening for MIM and used 33% of the gas needed for conventional atomization. PREDICTIVE COMPUTATIONAL FLUID DYNAMICS OF CLOSE COUPLED ATOMIZARION DIE R.Makineau, R.A.Berry. (Idaho National Engineering Laboratory, USA) The paper described a predictive 2 dimensional axisymmetric computational fluid dynamics model of close coupled gas atomization. The simulation was carried out for Ar and N atomization of a Ni base alloy and used to optimize for minimal gas consumption and maximum powder yield. Predicted and experimental results were compared. A NOVEL GAS ATOMIZATION NOZZLE FOR LIQUID METAL ATOMIZATION I.E.Anderson et al. (Ames Laboratory, USA.) A novel nozzle for close coupled high pressure gas atomization was described. It was reported that a high yield of fine powder was produced. A comparison was made with other processes in respect of gas flow, gas and metal consumption ratios and powder particle size distribution. The resunlts were discussed. CHARACTERIZATION OF LIQUID BREAKUP MECHANISMS FOR ATOMIZATION NOZZLES S.P.Mates, G.S.Settles. (Pennsylvania State University, Pennsylvania, USA) It was reported that several gas atomization nozzles had been characterized using flow visualization techniques with respect to primary disintegration of the metal stream. For each nozzle two mechanisms were MPR March 1997
41
identiEed. Some liquid is forced to the edge of the nozzle and is broken up by the gas flow. The remainder is less energetically disintegrated in the low speed wake. It was suggested that this may explain the wide particle size distribution found in some atomized powders.
High performance
materials
OPTIMIZATION OF SINTERING PARAMETERS FOR HIGH STRENGTH LOW ALLOY STEELS R.M. German et al. (Pennsylvania State University, Pennsylvania, USA) A study of processing Fe alloyed with Cu, Ni, MO and C was undertaken with the object of optimizing process conditions for enhanced properties at densities of about 7.1 gm.cm-‘. The need for identification of key parameters was emphasized and a variable search method was used to this end. These parameters were closely controlled and tolerances in others were broadened in order to reduce costs without loss in final properties SYNERGIES OF HIGH TEMPERATURE SINTERING AND ALLOY DEVELOPMENT FOR PM POWERTRAIN PARTS R.Shivanath, P.K.Jones. (Stackpole Ltd, Oakville, Canada.) High temperature sinterlng of parts was reviewed with reference to costs, properties and dimensional changes. The trend away from high temperature sir&ring was noted. It was argued that an advantage of high temperature sinterlng, alloying freedom, had been overlooked and that good alloying, together with good densification, was critically important. High temperature sintering was considered to be an important factor in the drive to replace steel parts with PM components. The Fe-Mn-C system was described. This system was reported to been used in a range of highly stressed automotive parts. DEVELOPMENT OF HIGH STRENGTH STEELS BY NBW ALLOYING AND SINTERJNG TECBNIQIJES E.Emst et al. (Sintermetallwerk Krebsoge GmbH, Radevormwald, Germany.) The need to avoid the use of free Ni, for environmental reasons, was noted. The elimination of free Ni powder from PM by use of prealloyed powders was discussed with reference to material properties. Alloying of a range of steel powders with Ni was investigated as a function of mechanical and fatigue The studies were properties. finalized with the production of an automotive part.
42 MPR March 1997
Warm compaction EFFECTS OF REPRESSING ON PROPERTIES OF WABM COMPACTED MATERIALS SYSTEMS S.R.Sun, K.R.Crouchman. (Pennsylvania Pressed Metals Inc., USA) Static and dynamic mechanical properties of warm compacted doublepressed/double sintered materials were discussed. Experiments intended to attain steel densities in excess of 7.55 gm.cmm3 were described.
Novel materials SCANDIUM OXYCARBIDE A NOVEL COMPONENT FOR BARD MATERIALS GRoiss et al. (Technical University, Vienna, Austria.) Scandium oxycarbide, Scz (0,C) , the carbide and oxide were discussed with reference to possible use as a constituent of hardmetals. It is noted that the existence of Scz(O,C) has been disputed but it is reported that the hardness of ‘DC is increased from 31 to over 50 GPa by small additions of Scz(O,C). It is suggested that the compound has a wide range of composition with a cubic structure and that Sc(O,N,C) could improve wear resistance of cemented carbides. ALUMINJUM NITRIDE-TUNGSTEN COMPOSITIONALLY GRADED MATERIAL FOR THERMAL BARRIER USE R.Watanabe et al. (Tohoku University, Sendai, Japan.) It was reported that an AlN/W compositionally graded material had been fabricated, layer-by-layer, from 1.39 pm AlN and 5.3 pm W powders, by HIP to full density at 200 MPa and 1850°C. Testing for thermal shock damage was monitored by accoustic emission techniques. The material was shown to have good thermal shock resistance and heat shield properties. STRUCTURAL EVOLUTION DURING SINTERING AND DIFFUSION OF COMPOSITIONALLY GRADED MATERIALS S.C.Yang. (Mando Machinery Corporation, Korea.) It was suggested that compositionally graded Fe/WC-Co materials could be used for wear resistant parts. Specimens were made by pressing and sintering and characterized for microstructure. The material was shown to have good potential for cost effective parts.
CORRELATIONS BETWEEN ISOSTATIC PRESS PARAMETERS AND CHARACTERISTICS OF CERAMIC PARTS C.S.Dumitrn, S,Sever. (University of Craiova, Romania.) Researches into production of parts from transluscent polycrystalline A120s, with respect to correlations between automatic isostatic pressing parameters and characteristics of pressed parts, were described. Optimum process conditions were established and outlined.
Refractory metal composites EFFECT OF COPPER PARTICLE SIZE ON SINTERING OF METAL INJECTION MOULDED TUNGSTEN-COPPER I.H.Moon et al. (Hanyang University, Korea.) The effect of Cu powder particle size on sintering of MIM W-Cu parts was investigated. Milled and mixed powders were compared. A range of Cu powders was used and simntering was evaluated in terms of Cu powder characteristics. The best sintering was attained with fine Cu powder giving densities in excess of 98%. THERMOMECHANICAL PROCESSING OF SINTERED TUNGSTEN-COPPER COMPOSITES EKOhrlner, B.Bryskin. (Oak Ridge National Laboratory, USA.) Properties of W-Cu alloys were discussed with respect to the need for high density and a structure comprising a continuous Cu matrix with W particles. Methods to attain this state, liqiud phase sintering, iniiltration, and these in combination, HIP and MIM, were outlined and it was noted that these do not always reach high density. Thermomechanical processing, to make W4O%Cu with high density, was investigated with regard to structural evolution. It was reported that hot extrusion gave material with high density.
Dimensional OM parts
control of
EFFECT OF SINTERING ON VARIATIONS IN PART DIMENSIONS AVavan et al. (Laval University, Canada) Literature on dimensional control of PM parts was reviewed, A statistical study, in a production environment, of the effects of green density, material and sintering parameters on dimensional variation in parts was described after which alterations were made to process conditions with a further evaluation. It was reported that the procedure could result in the attainment of closer dimensional tolerances.