POWDER METALLURGY PROCESS By: Madhu T.C. VIII Sem Dept. of Mechanical Engineering Siddaganga Institute of Technology Tumkur-3

CONTENTS Introduction. Steps involved in Powder Metallurgy. Factors governs the quality of Powder metallurgy components. Applications of Powder Metallurgy. Advantages.

INTRODUCTION Powder Metallurgy is the Science of producing metal powder and using them to make useful objects which will be having some outstanding characteristics than those produced by conventional methods. In this metal powders of different properties are subjected to a sufficiently a high temp and press and compacted so that a bonding takes place between them.

STEPS IN POWDER METALLURGY Production of Metal powders. Conditioning of powders. Compaction. Presintering. Sintering. Secondary operations.

Production of Metal powders Mechanical : Atomization. Shafting & Graining. Milling & Grinding. Physico-chemical: Reduction. Electrolysis.

Shafting & Graining : In this process the molten metal is poured in a vibrating sieve screen. The molten metal will disintegrate into small droplets and solidifies in an conditioned environment. Milling & Grinding : In this process the pulverisation of metal which are brittle in nature are crushed by using various types of crushers, rotary mills and grinders, In order to break down the metals by crushing and impact.

ATOMIZATION In this process the molten metal is mechanically forced through a nozzel by means of compressed Air. The molten metal will be automised into a very fine particles and solidification in air. The particle size can be controlled by varying the nozzel diameter, pressure and temperature of molten metal

Reduction : This is a method of obtaining powder of metals present in their oxide form. The oxides of these metals in their powdered form are reduced with carbon monoxide or hydrogen and the reduced powder is subsequently ground. Ex Fe3o4 + 4 Co -------> 3 Fe + 4 Co2 Cu2o + H2 -------> 2 Cu + H2o

Electrolysis : Electrolysis is similar to Electroplating technique. In this process the metal plates are placed in an electrolytic solution with one plate as anode and another plate as cathode. The conventional electrolysis process will be carried out. nfggfgh

Conditioning of powders The Conditioning of powders involve blending and mixing of metal powders. Different quantities of powder of metals or even non-metals are mixed thoroughly in this stage to obtain the desired properties like heat resistant, wear resistant, toughness …etc.

Compacting ( Briquetting ) : This is an important stage in powder metallurgy where metal powders are pressed into objects of desired shape and approximately to the final dimensions. Powders are compacted by using high pressures. Compacting is also designed to impart the desired level of porosity and to provide adequate strength for handling. Different techniques of Compacting powders into various shapes are 1.Die pressing 2. Roll pressing 3. Extrusion

Compression of metal powder by Compacting

Presintering : Presintering is the process of heating the compacted object to a temperature upto 0.5Tm of the base metal. Presintering is carried out on those components which need some machining after compaction. Sintering : Sintering is the process of heating the green compact or presintered compact to an elevated temperature usually in the range of 0.7 to 0.9 times of the base metal, with out applying the external pressure.

Secondary Operations : Sizing. Coining. Impregnation. Infiltration. Plating. Heat treatment.

Factors governs the quality of powder metallurgy components Size of powder particles and distribution of particles. Shape of metal powder. Fineness. Flowability. Compactibility.

Advantages of Powder Metallurgy technique Close dimensional tolerances and surface finish may be obtained. There is no unwanted loss of material during fabrication. Non-metallic substances can be introduced as required and in any proportion to get the desired properties. A wide range of properties can be obtained. High melting point metals and their carbides can be easily produced by this process. Porous objects like filters, oil impregnated bearings can be conveniently produced by this process.

Applications of Powder Metallurgy. Porous and Self - Lubricating Bearings Refractory parts such as filaments, cathodes, anodes used in electric bulbs x-ray tubes etc.. Toothed components like gears Welding rods and electrodes Carbide tipped tools