Effect of additives on plasma activated sintering of nanocrystalline alumina

Effect of additives on plasma activated sintering of nanocrystalline alumina

dimensional change of 0.16%. Increased dew point caused less dimensional growth but there was an increase in the depth of de-carburization which influ...

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dimensional change of 0.16%. Increased dew point caused less dimensional growth but there was an increase in the depth of de-carburization which influenced transverse rupture strength. Comparison was made with specimens sinterrd in endothermic atmospheres.

Plasma processing PLASMA COATING OF TUNGSTEN HEAVY ALLOYS WITH INCONEL OR 4030 STEEL A. Bose, I). Kapoor. (Parmatrch Corp. I+ taluma, California. (ISA). An investigation of the spraying of spherical Inconel718 and 4030 steel powders on to W heavy alloy substrates was described. The ohject,ives were to obtain dense co a t i n g s w i t,h g o o d interlacial integrity which were reported to hc attained. The, process, microstructures and the results of ‘push-out’ tests were discussed. EFFECT OF ADDITIVES ON PLASMA ACTIVATED SINTERING OF NANOCRYSTALLINE ALUMINA K.S. Mishra, A.K. Mukhcrjee. (Ilniversity of California. USA). Plasma activated sintrring of yAl.&,, at 1175 - 1500 C, with uniaxial st,ress up to 66 MPd, with additions of MgO or ZrO, was investigated. MgO was reported to enhance sint.ering. up t,o M.5':, density, whereas Zr02 did not. The mechanisms of densification w’ere discussed and sintering was shown to be slower than predicted. REACTIVE THERMAL SPRAYING OF MECHANICALLY ALLOYED NICRELSILICON POWDERS T.J. Tianen et al (Tamperr University of Ttchnolom, Finland). Thermal spraying of intermetallic compounds was discussed and it was shown that there may be decomposition of the compound on heating, and on cooling the compound does not reform due to rapid cooling. It is suggested that if MA powders were plasma sprayed. exothermic svthesis of the compound occurs and the heat evolved gives good densification and adhesion to the substrate. Resu1t.s for NiSi were described and discussed.

Process modelling SIMULATION OF DEFORAMTION PROCESSES IN POROUS AND POWDER MATERIALS UNDER PRESSURE B. Efros et al (Donet,sk Physico-Technical Inst., likraine). An investigation of high pressure deformat ion of powder and porous materials wits described and a system of

constitutive equations was developed, Hydrostatic treatment, hydromechanical setting and deformation were considered in respect of the models. Kesults were analyzed and the most effective use of high pressure was deduced.

and mechanisms of :
MODEL BASED DESIGN OF HOT ISOSTATIC PRESSING TO NEAR NET SHAPE

A NEW AUSTENITIC STAINLESS STEEL WITH IMPROVED CORROSION AND WEAR PROPERTIES

J.J. Conway et al (Crucible Compaction Metals, Oakdale, Pennsylvania, IZA) Shape distortions, caused by temperature and pressure shielding by the container, in HIP, were discussed with respect to empirical methods and part design to attain the correct shape, Investigations were described. A modelling technique for HIP part design, in which mechanical and thermal properties of the powder are taken into account, was outlined. It-was reported that three or four iterations lead to a satisfactory design.

1’. Nurthen et al (Powdrex Ltd. Tonbridge, Kent, I JK) Applications of austenitic :JOO and martensitic 400 stainless steel series for corrosion and wear resistance. but lower corrosion resistance, respectively were discussed. I~rvelopmrnt of a new st,eel with wear and corrsion resistance hnth improved was reported.

PRESSURE-DENSIFICATION PLOT FOR COMPRESSION AND COMPACTION AND APPLICATION TO HIP .J.V. Kumar, C.S. Kumar (Mishra Dhatu Nigam Ltd, Hyderabad, India). Dir compaction of single spheres was discussed with regard to contact area and shrinkage related to initial porosity. It was shown that it is possible to convert local deformation characteristics of an unconst~rdined sphere into a plot depicting densification of real powders which represents minimum dcnsification at any given pressure. Application to HIP was outlinrd.

Corrosion behaviour stainless steel

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PM STAINLESS STEEL BASED ALLOYS WITH IMPROVED CORROSION RESISTANCE .J.H. Keinshagen, T..J. Rockius (Amrtek Inc. Wallingford, Connecticut, I ISA). Reasons for lower corrosion resistance of PM stainless steels, compared with wrought alloys, were out,lined and discused with reference to porosity and the presence of carbides and/or nitrides. Properties of a group of stainless steels, with improved corrosion resistance were introduced and were said to have sintering characteristics similar t.o convrnt,ional steels. Processing for maximum corrosion resistance was outlined. EFFECT OF PORE MORPHOLOGY ON CORROSION OF SINTERED STAINLESS STEEL T. Mathiesen, E. Maahn. (Technical Lrniversity of Denmark, Denmark). Investigations of corrosion properties

Machining and machinability SHELF LIFE OF MANGANESE SULPHIDE POWDER AND MIXTURES CONTAINING MANGANESE SULPHIDE D.S. Madan, A. Fitzpibbon (Elkem Metals Co, Pittsburg, Pennsylvania, ITSA). MnS powder was reported to absorb moisture in storage and to rf:quire protection. The cftects of this moisture were evaluated. So-called rust spots were investigated. It was reported that, under appropriate storage conditions. t he r e was no w a t e r contamination. It was recommended t,hat MnS is stored in sealed containers with a dessicant IMPROVEMENT OF MACHINABILTY SINTERED STEEL BY RETAINED GRAPHITE PARTICLES

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K. Ogura et al (Kawasaki Steel (:orp. Kawasaki, Japan). It was reported th;d a new t_ype of Fe powder material. with added (:u and graphite, showed improved machinability. This was at.tributed to the retention of graphite in pores after sintcring. Increased tool life for cutting the steel was reported. The reason for the retention of graphite was said to bc low difliision in austenite. DISPERSION STRENGTHENING OF CERAMIC CUTTING TOOLS FOR IMPROVED TOOL LIFE S.B.S. Kumar et al (Indian Inst. of Technol ogy, Kanpur, India). It was reportctd that a zirconia toughnened alumina cutting tool had widened the application of ceramic tools. This was attributed to a stress induced trtragonal to monoclinic transformation at the cutting edgc which enhanced the toughness and minimized chipping. The perf~)rmarru~ of the tool material in cutting alk~y steel was tlf5criheti. MPR October 1995

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