Microstructures and properties of ceramic reinforced super-duplex stainless steels

Microstructures and properties of ceramic reinforced super-duplex stainless steels

Wet powder pouring of parts, in which metal powder mixed with binder and a fluid carrier is poured into a mould, was described. After removal of the c...

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Wet powder pouring of parts, in which metal powder mixed with binder and a fluid carrier is poured into a mould, was described. After removal of the carrier by evaporation, debinding and sintering the parts were consolidated by HIP. The properties of a range of materials were determined and the results were presented and discussed.

Measurement

and control

PLASMA SPRAY ATOMIZATION OF ALUMINIUM ALLOY MATRIX COMPOSITE POWDERS K.A. Khor, F. Boey (Nanyan Technological University, Singapore) Plasma spray production of Al base MMC powders was described. Alloy powders with additions of Sic were granulated before plasma spraying. Studies of the effects of process conditions were reported. The powders with Sic were said to have potential in circumventing some of the problems found in conventional methods used to produce MMCs. DILATOMETRY STUDIES OF WATER ATOMIZED STAINLESS STEEL POWDERS

CONSTITUTIVE EQUATIONS IN NUMERICAL SIMULATION OF DIE PRESSING AND SINTERING H. Riedel et al (Fraunhofer Inst. Werkstoffemechani, Frieburg, Germany) Studies of solid state sintering were reviewed with the objective of establishing equations for use in finite element analysis. Transport mechanisms in sintering stages and grain growth were considered. Model predictions were compared with experimental data. Some agreements and some discrepancies were reported. PRESSURE FRICTION AND DENSITY DURING AXIAL POWDER COMPACTION E. Ernst, D. Barnekow (Krebsiige Sinterholding, Radevormwald, Germany) Effects of friction between powder and tools in causing pressure variations in compacts were discussed with respect to resistance of the powder to deformation, relative tool movements and lubrication. Experiments on axial compaction were described in which various factors were measured. Attempts were made to bridge the gap between theory and practice of compaction.

Modelling of sintering PHASE EQUILIBRIA AND SINTERING OF CEMENTED CARBIDES B. Uhrenius (Swedish Inst for Metals Research, Stockholm, Sweden) Relationships between composition and calculated phase equilibria in WC-Co, WCNi/Fe and WC-Co/Ni/Fe were discussed with respect to C content and process steps. Comparison was made with measured data. Prediction of constitution of sintered systems was possible. Account was taken of non-attainment of equilibrium. IN-SITU REINFORCED BORIDE AND CARBIDE BASED HARD MATERIALS

J. Telle (Rheinisch-Westfalisch Technische Hochschule, Aachen, Germany) Development of microstructures in Si-TiB-C during sintering was investigated with regard to the formation of platelets. It was reported that annealing TiBz-WzB5 compacts gave solid solutions from which WaBa platelets were precipitated. Some improvement in properties was reported.

RHEOLOGICAL CHARACTERIZATION OF METAL POWDERS AFTER VARIOUS LOADING PATHS

PHASE FORMATION IN COLDEXTRUDED AND ANNEALED TITANIUM ALUMINIDE POWDER MATERIALS

P. Mosbah et al (UJF/INPG/CRNS, Genoble, France) An investigation in which various compaction methods were used in order to characterize the mechanical behaviour of Fe powders, was described. Die compaction data and compact anisotropy were analysed and used to develop constitutive compaction equations.

T.J. Jewett et al (GKSS Research Centre, Geesthact, Germany) Phase formation during annealing of ‘f48at%Al and Ti-48at%All2%Cr was investigated by X-ray analysis. The formation of TiAl and TiAls was shown to pass through intermediate stages, forming transient TiAls and TiAlz, Cr reduces reaction rates.

NON-DESTRUCTIVE INVESTIGATION OF PM MATERIALS BY MAGNETOACOUSTIC METHODS

THREE-DIMENSIONAL SIMULATION OF POWDER CHARACTERISTICS AND COMPACTION BEHAVIOUR

REACTION BETWEEN PARTICLES OF DIFFERENT HEAT RESISTANCE STEELS

A Popov et al (Bulgarian Academy of Sciences, Sofia, Bulgaria) A non-destructive testing method based on the emission of magneto-acoustic signals was described. Mathematical analysis was used to assess the parameters. Application to PM materials was discussed.

S. Shima, H. Kotera (Kyoto University, Kyoto, Japan) A 2-dimensional model of powder compaction was described and extended to a 3-dimensional study based on powder modelling. Plastic deformation and interparticle friction were taken into account. The method used gives simulation of closed die, isostatic and 3dimensional compaction at arbitrary stress ratios. Comparisons were made with experiment. It was shown that calculated pressures were less than experimental values.

A Fleming et al (Babcock Energy Ltd, Renfrew, UK) The use of compositionally graded joints in chemical plant, in order to withstand differing temperature regimes by minimizing thermal stresses, was discussed. It was reported that HIP had been used to fabricate such joints in heat resistant steels. A diffusional model was used to describe microstructural changes which was confirmed by observations of microstructures and measurements of mechanical properties.

K.A. Khor, N.H. Lob (Nanyang Technological University, Singapore) Sintering of 316L stainless steel was studied by dilatometer at various heating rates. Slow rates were reported to give the largest contractions. Sintered and fractured specimens were examined metallographical. Slow heating rates gave the lower porosity and smaller pores.

APPLICATION OF STATISTICS TO STUDY OF HARDNESS MEASUREMENTS OF PM STEELS J.M. Torralba et al (Polytechnical University of Madrid, Madrid, Spain) Assessment of the homogeneity of PM steels by hardness measurements was discussed as a function of factors affecting hardness variation. Results of testing were analysed statistically in detail. A procedure was developed which was reported to be useful in sintering studies and quality control.

46 MPR January 1995

MODELLING OF COLD COMPACTION OF METAL POWDERS M.D. Riero, J.M. Prado (Polytechnic University of Catalonia, Barcelona, Spain) The Cam-Clay model was used to characterize mechanical response of Fe powder. Finite element analysis was used to study density variation. Simulated and experimental results were compared.

MICROSTRUCTURES AND PROPERTIES OF CERAMIC REINFORCED SUPER-DUPLEX STAINLESS STEELS MJ. Talvities, V.K. Lindroos (Helsinki University of Technology, Espoo, Finland) An investigation of reactions between AlaOs, CrsCz and Tic reinforcements in HIP

stainless steel was described. It was shown that AlzOs did not react with the matrix, CraCe reacted strongly giving thick films of brittle reaction product and Tic reacted only slightly. The bond strength between Tic and the matrix was high making Tic the most effective reinforcement.

Aluminium

Alloys

ANALYSIS OF SURFACE OXIDE FILMS ON TERNARY ALUMINIUM SILICON ALLOYS J.L. Estrada, J. Duszcyk (Delft University of Technology, Delft, The Netherlands) An investigation of the composition and thickness of surface films on air and Ar atomized ternary Al-BO%Si alloys was described. The ternary additions were Cu, Mg, Fe or Ni. Ar atomized powders had thinner oxide films, lower density and the powders were of lower surface area. Alloy composition affected the composition of films but thickness was determined by atomizing atmosphere. MECIIANICAL ALLOYING APPLIED TO ALUMINIUM-TITANIUM-BERYLIUM ALLOY F. Ravel et al (CEA, Bryeres de Chatel, France) Potential applications for Al-T-Be alloys were discussed with reference to properties.

It was reported that mechanical alloying had been used to prepare binary and ternary alloy powders which were characterized by electron microscopy and X-ray analysis. Amorphization and nanocrystallization were shown to occur during MA. A mathematical model of MA was outlined. MECHANICAL PROPERTIES OF RAPIDLY SOLIDIFIED ALUMINIUMTITANIUM-IRON-CHROMIUM ALLOYS

properties of Al-8%Ti-S.l%Zr were superior to those of AI-8XTi. The relationship between the enhanced properties microstructure were discussed.

Steel EFFECT OF ACCELERATING AND INHIBITING ADDITIONS ON SINTERIN’G OF CARBON STEELS

T. Matsumoto et al (Tohoku University, Sendai, Japan). It was reported that Al-Ti-Fe-Cr alloys, fabricated by extrusion from gas atomized powders had higher strength than Young’s modulus than conventional PM alloys. This was attributed to fine scale microstructure, grain size and dispersion of inter-metallic phases.

S.M. Metchkova et al (MK Ltd, Sofia, Bulgaria) It was reported that elements of group II of the periodic table accelerated decomposition of CO in contact with Fe and the elements of groups V, Vl and VII, inhibited decomposition. These findings were related to the carburization of Fe during sintering and to the pressure of accelerating or inhibiting additives. Influence on pearlite was also established.

EFFECTS OF ZIRCONIUM AND VANADIUM ON MECHANICAL PROPERTIES OF ALUMINIUMTITANIUM

A MODEL FOR IRON-CARBONPHOSPHORUS POWDER ALLOYS

I.H. Mood et al (Hanyang University, Seoul, Korea) It was noted that the addition of V or Zr to Al-Ti alloys stabilized TiAls disperosids formed during mechanical alloying. It was reported that the high temperature

V.G. Ljulko et al (Don State Technical University, Rostow-on Don, Russia) Studies of Fe-(0.5 to 2.5)%P- (0.5 to 2.5)%C powders and sintered compacts were described. A computerized model to describe properties in relationship to impurity levels was given.

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MPR January 1995 47