Advantages of powder Metallurgy
Advantages of powder Metallurgy:
- The processes of powder metallurgy are quite and clean.
- Articles of any intricate or complicated shape can be manufactured.
- The dimensional accuracy and surface finish obtainable are much better for many applications and hence machining can be eliminated.
- Unlike casting, press forming machining, no material is being wasted as scrap and the process makes utilizes full raw material
- Hard to process materials such as diamond can be converted into usable components and tools through this process.
- High production rates can be easily achieved.
- The phase diagram constraints, which do not allow an alloy formation between mutually insoluble constituents in liquid state, such as in case of copper and lead are removed in this process and mixtures of such metal powders can be easily processed and shaped through this process.
- This process facilitates production of many such parts, which cannot be produced through other methods, such as sintered carbides and self-lubricating bearings.
- The process enables an effective control over several properties such as purity, density, porosity, particle size, etc., in the parts produced through this process.
- The components produced by this process are highly pure and bears longer life.
- It enables production of parts from such alloys, which possess poor cast ability.
- It is possible to ensure uniformity of composition, since exact proportions of constituent metal powders can be used.
- The preparation and processing of powdered iron and nonferrous parts made in this way exhibit good properties, which cannot be produced in any other way.
- Simple shaped parts can be made to size with 100 micron accuracy without waste
- Porous parts can be produced that could not be made in any other way.
- Parts with wide variations in compositions and materials can be produced.
- Structure and properties can be controlled more closely than in other fabricating processes.
- Highly qualified or skilled labor is not required. in powder metallurgy process
- Super-hard cutting tool bits, which are impossible to produce by other manufacturin processes, can be easily manufactured using this process.
- Components shapes obtained possess excellent reproducibility.
- Control of grain size, relatively much uniform structure and defect such voids and blowholes in structure can be eliminated.
LIMITATIONS OF POWDER METALLURGY:
- Powder metallurgy process is not economical for small-scale production.
- The cost of tool and die of powder metallurgical set-up is relatively high
- The size of products as compared to casting is limited because of the requirement of large presses and expensive tools which would be required for compacting.
- Metal powders are expensive and in some cases difficult to store without some deterioration.
- Intricate or complex shapes produced by casting cannot be made by powder
- metallurgy because metallic powders lack the ability to flow to the extent of molten metals.
- Articles made by powder metallurgy in most cases do not have as good physical properties as wrought or cast parts.
- It may be difficult sometimes to obtain particular alloy powders
- Parts pressed from the top tend to be less dense at the bottom.
- A completely deep structure cannot be produced through this process.
- The process is not found economical for small-scale production.
- It is not easy to convert brass, bronze and a numbers of steels into powdered form.
APPLICATIONS OF POWDER METALLURGY:
The powder metallurgy process has provided a practical solution to the problem of producing refractory metals, which have now become the basis of making heat-resistant materials and cutting tools of extreme hardness. Another very important and useful item of the products made from powdered metals is porous self-lubricating bearing. In short, modern technology is inconceivable without powder metallurgy products, the various fields of application of which expand every year. Some of the powder metal products are given as under.
- Porous products such as bearings and filters.
- Tungsten carbide, gauges, wire drawing dies, wire-guides, stamping and blanking tools, stones, hammers, rock drilling bits, etc.
- Various machine parts are produced from tungsten powder. Highly heat and wear resistant cutting tools from tungsten carbide powders with titanium carbide, powders are used for and die manufacturing.
- Refractory parts such as components made out of tungsten, tantalum and molybdenum are used in electric bulbs, radio valves, oscillator valves, X-ray tubes in the form of filament, cathode, anode, control grids, electric contact points etc.
- Products of complex shapes that require considerable machining when made by other processes namely toothed components such as gears.
- Components used in automotive part assembly such as electrical contacts, crankshaft drive or camshaft sprocket, piston rings and rocker shaft brackets, door, mechanisms, connecting rods and brake linings, clutch facings, welding rods, etc.
- Products where the combined properties of two metals or metals and non-metals are desired such as non-porous bearings, electric motor brushes, etc.
- Porous metal bearings made which are later impregnated with lubricants. Copper and graphite powders are used for manufacturing automobile parts and brushes.
- The combinations of metals and ceramics, which are bonded by similar process as metal powders, are called cermets. They combine in them useful properties of high refractoriness of ceramics and toughness of metals. They are produced in two forms namely oxides based and carbide based.