Volume 4 No.2 July 2001

Profile

Sintering Science and Technology:
Activities at IIT Kanpur

Since 1976 Indian Institute of Technology Kanpur has been consistently active in powder metallurgy education and research. In this article, the facilities available and past and present research activities at I.I.T. Kanpur are outlined, with particular emphasis on sintering science and technology.

Introduction

The Department of Materials and Metallurgical Engineering at I.I.T. Kanpur offered a limited programme of education and research in powder metallurgy from the very beginning. Since 1976, the Institute has expanded its powder metallurgy facilities and research programmes. Research and development activity in the area of sintering science and technology at I.I.T. Kanpur dates back to the time when the powder metallurgy laboratory was established.

Eleven Ph.D. and thirtyseven M.Tech. scholars have so far completed their thesis work in the powder metallurgy area and have published more than 200 papers.

The powder metallurgy laboratory is active in consultancy work for industries and it was recognised by the IITs to enter into agreement with the Planning Commission, Government of India for product development in the area of sintered cermets (Grant Rs. 93.00 Lakhs). At present the P/M activity at IIT Kanpur is recognised not only in India, but also world over.

Facilities

The powder metallurgy facilities at IIT Kanpur are designed with versatility in mind and include equipment for powder preparation, characterization and blending, milling, pressing and sintering, in addition to facilities for product evaluation. From the powder stage, each major powder operation can be carried out in the laboratory. For characterization, costly equipments like Coulter Counter, B.E.T. analyser, scanning and transmission electron microscopes, Instron, M.T.S., SATEC creep testing unit, and X-ray diffraction units are situated in the ‘Advanced Center for Materials Science’, which is a central facility of the Institute. The powder metallurgy laboratory has its own metallographic preparation facilities, particularly suited for the examination of sintered alloys. Equipments which the laboratory houses include a water atomizer (Davy-Loewy, UK), 20 ton hydraulic press, controlled atmosphere sintering furnaces up to 2200°C capability ( Heraus, Elatec and in-house), Brinell cum Vickers hardness tester, green strength tester ( Hoganas Custom made), double cone blender (Netzsch), vacuum oven, infrared gas analyser (Riken, Japan), Lectrodryer, transverse rupture strength tester (Karl Frank), microhardness tester (Leitz), impact tester (Wolpert), dew point meter (Shaw, UK), controlled atmosphere high temperature dilatometer (Orton, USA), DTA up to 1450°C range (Netzsch), powder sampler (Alfred Fritsch), Coercimeter, tap density meter (Engelmann), infrared pyrometer (Wahl), precision balances (Mettler), densometer (Fairey Tecramics), Fischer Subsieve sizer, oxygen monitor (Ametek), short bar fracture toughness measuring unit, potentiostat, image analyser and magnetic saturation measurements.

Research on Sintering Science & Technology

Some of the major investigations carried out at IIT Kanpur are:

  • Sintering of Single component systems
  • Sintering of Binary alloys
  • Sintering of Ternary and multicomponent alloys
  • Sintering of Metal-Metal particulate composites
  • Sintering of Metal-Ceramic particulate composites
  • Sintering of Ceramic-Ceramic particulate composites
  • Structure-properties relations in fully dense powder metallurgy alloys

Research was carried out on sintering of loose stacked spherical iron powder in non-isothermal conditions to see the validity of surface diffusion mechanism and also how far a change in sintering atmosphere is affecting the kinetics. It was found that change in atmosphere from dry hydrogen (reducing) to argon does not significantly affect the kinetics of neck growth. This is of significance as costly hydrogen atmosphere can be successfully replaced in many cases, after initial sintering by cheap nitrogen.

Among binary alloys our main stress was copper based binary systems (additives being Ag, Si, Sn and Pb), where the role of phase diagrams in predicting the sintering response was focused.

For study on ternary and multicomponent systems, emphasis was placed to copper-base alloys containing transition metal additive and Fe-P-X (X = Mo, Ni, Cu) systems. In the field of sintered titanium alloys, alloying elements like Al and Sn were exploited, where transient liquid phase sintering was carried out.

Sintering of Metal-Ceramic composites:

The research work in the area of Metal-Ceramic Composites has been quite substantial and these can be broadly categorized as follows:

  • Pb based composites
  • Al and Al-alloy based composites
  • Stainless steel based composites
  • High speed steel based composites
  • Tungsten carbide based cemented carbides
  • Cemented binary and ternary refractory borides

A detailed investigation of modification of both carbide and binder phases in WC-10Co (16.5% vol.) was carried out in order to develop equivalent steel cutting grade hard metals. The hard phase, WC, was partially replaced by TiC and the binder phase, Co, by Ni and Mo. The volume percentage of hard phases WC and TiC were kept in all alloys as 63% and 20% respectively. Sintering studies were made in both a hydrogen atmosphere and a vacuum at different temperatures in the range of 1450-1500°C. The partial substitution of cobalt in WC-8TiC-12Co hard metal by nickel necessitated addition of molybdenum either in elemental or carbide form, the latter being a better composition. The hard metal shows equivalent properties with those prepared using (W,Ti)C solid solution.

Sintering of Ceramic-Ceramic composites

Ceramic-Ceramic composites are a special group of materials where the identity of each of the two ceramic phases are not only preserved, but the intention is to improve properties over and above those expected from conventional technical ceramics. Our research team has processed mullite based particulate composites containing ZrO2 (0-25 vol. %), where the latter imparts transformation toughening. The mullite powder used was very fine (Av particle size 1.3 mm) derived after sol-gel processing. Results confirmed that an optimum ZrO2 addition (10 vol.%) enhanced the sinterability and transverse rupture strength. In addition, we have also produced Millite-ZrO2 composites from electrofused mullite powders and after reaction sintering of Zircon with Al2O3. These products are far more cheaper than those based on relatively costly sol-gel powder. Although the fracture toughness and dielectric constant values are somewhat lower, there is no change in thermal shock resistance. Such economical routes are, therefore, attractive for their applications as technical ceramics.

Structure properties relations in fully dense powder metallurgy alloys:

Under this major theme, the main thrust has been on detailed investigation of microstructure-mechanical properties relations of the following alloys:

  • Dispersion strengthened Aluminium with Al4C3 (DISPAl)
  • Dispersion strengthened copper with Al2O3 (GLIDCOP)
  • Microcrystalline rapidly solidified 7091 Al-alloy

The drastic microstructural control offered by P/M processing has given enough new materials for physical metallurgists to unravel their mysteries.

Powder Metallurgy Education

IIT Kanpur has been unique in offering a number of undergraduate and postgraduate level courses in the area of powder metallurgy in general.

The Undergraduate courses are:

Foundry and Powder Metallurgy
Advances in Powder Metallurgy

The Post graduate courses are:

Sintering and Sintered Products
Design of Sintered Products
Sintered Tool Materials

Every B.Tech. student of the Department does undertake laboratory experiments in the area of powder metallurgy.

Books Published

  • Materials for Advanced Energy Systems, (Ed. G.S. Upadhyaya), Indian Institute of Technology, Kanpur, 1984
  • Sintered Metal-Ceramic Composites, (Ed. G.S. Upadhyaya), Elsevier Science Publishers B.V., Amsterdam, 1984
  • Manganese in Powder Metallurgy Alloys, Manganese Centre, Paris, 1986 (G.S. Upadhyaya)
  • Sintering of Multiphase Metal and Ceramic Systems, (Ed. G.S. Upadhyaya), Science Tech, Publication, Vaduz, 1990
  • Powder Processing of High Tc Oxide Superconductors and their Properties, Trans. Tech. Publications Ltd., Switzerland, 1992 , (G.S. Upadhyaya & A.C. Bajpei)
  • Nature and Properties of Refractory Carbides, Nova Science Publishers, Inc, 1996 (G.S. Upadhyaya)
  • Powder Metallurgy Technology, Cambridge International Science Publishing, Cambridge, U.K, 1997 (G.S. Upadhyaya)
  • Dhatuo Ka Itihas, U.P. Hindi Sansthan, Lucknow, 1997(in Hindi) (G.S. Upadhyaya)
  • Cemented Tungsten Carbides: Production Properties and Testing, Noyes Publications, Fairfield, New Jersy, USA, 1998 (G.S. Upadhyaya)
  • Sintered Metallic and Ceramic Materials: Preparation, Properties and Applications, John Wiley & Sons Ltd., U.K., 2000 (G.S. Upadhyaya)
Current Research
Currently, following postgraduate theses are being undertaken in the laboratory:
  • Role of Crystallographic Orientation in Microstructural Evolution in Sintered Premix and Pre-alloyed Bronzes
  • Environmental Degradation (Corrosion and High Temperature Oxidation Resistance) of Super-Solidus Sintered ODS (Y2O3 added)-Stainless-Steel
  • Effect of Thermo-Mechanical Treatment on Stereological Aspects of Tungsten Heavy Alloys
  • Activated Densification of Intermetallic Bonded-B Doped Refractory Metals

G.S. Upadhyaya
Dept. of Materials & Metallurgical Engineer


 


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