13 Main Advantages and Disadvantages of Powder Metallurgy | Applications of Powder Metallurgy
What is Powder Metallurgy? | Advantages and Disadvantages of Powder Metallurgy | Applications of Powder Metallurgy | Powder Metallurgy Process
What is Powder Metallurgy?
Powder metallurgy is the process of creating metal parts from small metal powders. The powder is heated until the particles fuse together, and then the needed shape is molded.
The process typically results in a stronger metal, and it reduces the amount of wasted metal since the metal is fused to make it, as opposed to using a mould and melting the pieces
Powder metallurgy offers a new and innovative way for precision metal parts to be made. It has been around since the 1920s.
Many materials can be made into a powder and then be reconstituted as a solid, and in powder metallurgy, steel is one of those materials.
The steel powder goes through a process known as compacting and sintering, which means that the atoms are being compressed together, to form the shape they need to be in.
This process is done at a lower temperature than normal, like 400 degrees Fahrenheit or so.
There are many metal alloys that can be made into powders by coal or electric power metallurgy.
The metal alloys can be made into powders that can then be remelted and cast into the desired shape.
This process can be used to make bronze, aluminum, and titanium. Powdered metal can be used to make objects lighter, stronger, and more durable.
Powder Metallurgy Process
Powder Metallurgy is an advanced manufacturing process that was developed to overcome the limitations of traditional metalworking.
With the process, metal powder is added to a metal binder and then heated until they fuse together and form a solid piece of material.
The resulting product is easier and less expensive to produce while increasing its strength and durability.
The powder metallurgy process is a manufacturing process that uses a machine called a compactor to reduce the size of metal powder.
The machine then forces the metal particles together into a small compact metal object.
Steps in powder metallurgy:
- Powder production,
- Secondary operations
Metal Powder Production
Making metal powders is the initial stage in the whole powder metallurgy (PM) process. Powder manufacturing involves four major processes: solid-state reduction, atomization, electrolysis, and chemical.
Solid-State Reduction is a term that refers to the process of reducing. Selective ore is crushed, often combined with carbon, and fed through a continuous furnace in solid-state reduction.
A reaction occurs in the furnace, removing the carbon and oxygen from the powder, resulting in a cake of sponge metal that is crushed, separated from any non-metallic debris, and sieved to create powder.
Because there is no refining procedure, the purity of the powder is determined by the purity of the raw components.
The irregular sponge-like particles are soft and easily compressible, resulting in compacts with high pre-sintering (“green”) strength.
Molten metal is divided into microscopic droplets and swiftly frozen before they come into touch with each other or a solid surface in this procedure.
A thin stream of molten metal is often destroyed by the collision of high-energy jets of gas or liquid.
In theory, the technique is applicable to any metal that can be melted and is commercially used to produce iron, copper, alloy steels, brass, bronze, low-melting-point metals such as aluminum, tin, lead, zinc, and cadmium, and, in some cases, tungsten, titanium, rhenium, and other high-melting-point materials.
Many metals can be deposited in a spongy or powdery state by selecting appropriate parameters such as electrolyte composition and concentration, temperature, and current density.
Additional processing—washing, drying, reducing, annealing, and crushing—is frequently necessary, resulting in high-purity and high-density powders.
The principal metal generated by electrolysis is copper, but iron, chromium, and magnesium powders are also created in this manner.
Electrolysis is typically confined to high-value powders such as high-conductivity copper powders due to the related high energy expenditures.
Oxidation-reduction, precipitation from liquids, and thermal degradation are the most frequent chemical powder treatments.
The powders generated can have a wide range of characteristics while maintaining tightly regulated particle size and form.
Because of the holes found inside individual particles, oxide-reduced powders are sometimes described as “spongy.”
Solution-precipitated powders can have very narrow particle size distributions and are very pure. Carbonyls are most often processed via thermal decomposition.
After milling and annealing, the purity of these powders exceeds 99.5 percent.
Metal Compaction Process
After the metal powder has been created, it is compacted using a process called compaction. The purpose of compaction is to form a dense object out of the powder.
This is done by subjecting the powder to high pressure and high temperature in a closed die.
Compaction enhances densification of the metal powders and improves properties such as density, hardness, strength, ductility and yield strength.
Compaction is a key process in powder metallurgy because it increases the overall mechanical properties of the powder by causing the metal atoms to line up in rows, giving rise to a strong solid structure with high density.
The process occurs at temperatures as high as 1600 C, and pressures from 100 to 400 kPa.
Metal Sintering Process
Sintering is an operation used to consolidate powders into a dense solid state. Sintering occurs when higher temperatures are reached and affects the grain size of the powder particles.
The sintering process is the last step in the powder metallurgy process and carries out the final stages of densification.
Sintering involves heating to temperatures between 500-1400 C and pressures of up to 1000 bars, depending on powder composition.
Increasing the volume of the powder particles increases its density, thereby reducing its overall weight by making it lighter.
This process is especially important in certain high-value products such as balls made from golf clubs or aircraft.
Temperatures above 1200 C result in the destruction of the internal pores by means of sintering and so cannot be used.
As a result, densification can occur only at temperatures lower than that value. When particles reach a minimum size, their physical behavior changes from being brittle to ductile with increasing temperature.
There are a number of secondary operations. Materials may be melted and cast using modern casting machines, or added as an alloy to provide desired properties.
Powder metallurgy can also apply additives to produce magnetic, brittle, porous or plastic metal products.
These additives can improve electrical conductivity, form a protective coating for the powder particles and increase the diffusion rate of specific elements in the material.
Alternatively, the powder may contain grains of metal that are separated by a matrix of magnesium oxide or silicon carbide.
High-purity metals such as silicon and gallium can be recovered from these powders, for example. Metals such as copper, tungsten and titanium dioxide can be used to enhance the metallurgical properties of metals.
Uranium can be added to steel powders in order to increase hardness.
Metal powders can also be mixed in cyanide to produce a cyanide-based salt that can be used as a lubricant or an alloying agent.
Most metal-based powder is made for injection molding, extrusion and foundry-casting. The metal powder must meet strict criteria for purity and quality in order to be successfully used in these manufacturing processes.
Injection molding is the most commonly used process in the manufacture of metal-powder-based components.
The injection molding process uses a “tool” that contains a cavity slightly larger than the part to be made.
The cavity is filled with material, plasticized to assure that it will flow through the tool in one direction. A device called an injection molding machine is then used to manipulate this molten metal.
Extrusion is used in the production of metal-powder-based materials for automotive components such as wheels, chassis frames and suspension systems.
Throughout the process, the powder is bonded to various types of resins and casting compounds to provide strength, adhesion and appearance.
Processes that use metal powders as an ingredient in the manufacture of metals include those used in foundry-casting.
The foundry is a heated furnace or enclosed building used to melt metals. It uses a solid fuel with metal salts added, such as lead, tin and antimony.
The molten metal is then poured into molds. As it cools, it re-solidifies into a solid metal or alloy.
The strength of a powder depends on the type of microstructure formed as a result of deformation.
If the grains were not bonded together and will tend to move freely, then fracture and failure would result. The microstructure formed is dependent on several factors.
Several important properties for metal powder are density, ductility, compressibility and strength.
Industrial applications of metals often demand metal powders with greater density but which also exhibit superior properties for performance in mechanical or chemical systems.
The most important of these properties in terms of the design and performance are strength, ductility, density and hardness.
High-quality metal powder has a high density, which requires the use of methods to densify the powder; this may involve different technologies such as compaction and sintering.
Applications of Powder Metallurgy
The uses of powder metallurgy included;
1. Vehicle parts:
Heavy Duty Trucks with aluminum body structures for the unsplit and split axle.
2. Medical instrumentation:
Transducers for ultrasound, MR, X-ray machines etc.
To make components such as bomb bays, cooling boxes and panels, wing leading edges, fuselage bulkheads and cargo doors, landing gear nose wheel assemblies; etc.
4. Steel casting:
Titanium, uranium, and other special alloy castings.
A relatively low-cost method to produce low-melting metal alloys such as ferrite and cemented carbides.
Precision machined components for civil engineering applications including cast iron dies and tubes used in interior structural steelwork of bridges, buildings, tanks etc.
Advantages and Disadvantages of Powder Metallurgy
Advantages of Powder Metallurgy
- There is no wastage of raw material
Powder metallurgy is the first step where waste of material is eliminated, as powder particles are less than 50 microns in size.
The small powder particles are pressed together at a low temperature to form a large block of metal.
- Provides high strength and hardness with very low weight
Since PM can withstand high temperatures without melting, it has become an ideal material for applications such as aerospace engineering, medical equipment, and nuclear reactors because of their potential for increasing the efficiency of systems while reducing their weight.
- Products made by PM generally do not require further finishing
Because of the low melting point of powders, the metals can be cast into different shapes and sizes for further processing.
- Less expensive to produce
Less expensive to produce than conventionally manufactured metal products such as steel
The use of PM allows the production of metals with very high purity required by most industries. There is the overall economy since material waste is minimal.
- Product’s composition may be efficiently regulated
Production is based on chemical precipitation. Therefore, the composition of the powder may be easily controlled according to the desired end product.
It is possible to obtain close dimensional tolerance
Due to high purity levels and effective production techniques, PM is generally considered a safe and environmentally friendly manufacturing process for metals.
The parts can be manufactured in a clean, bright, and ready-to-use state.
- Long life cycle
Since the materials are produced in thermodynamically stable states, they can be repaired or restored if they become damaged or worn out over time.
- Minimization of waste in the manufacturing process
Due to the presence of excess particles in the case of solid-state reduction, it is possible to reduce the amount of waste from raw materials while increasing yields at the same time.
- Low power consumption
In an electric arc furnace used for metal powder production, less power is consumed because a larger surface area can be obtained from smaller quantities of raw material.
- Increased productivity
The use of powder metallurgy techniques minimizes investment in resources and equipment by increasing the speed and accuracy of production.
A wide variety of characteristics, such as porosity, density, and so on, may be efficiently accomplished.
Disadvantages of Powder Metallurgy
- Low resistance to chemicals
PM has poor corrosion resistance due to its high porosity, which makes it susceptible to corrosion.
When compared to cast or machined components, the mechanical characteristics of the parts are of inferior grade.
- High cost of maintenance
Machines used in this process are expensive, which makes replacement difficult in case of any damage or excessive wear on the machine.
Tooling costs are typically prohibitively expensive and can only be justified in bulk manufacturing.
- Low surface strength
Due to the presence of numerous pores in powder metallurgy products, the surface strength is low.
It is not suitable for machining, and therefore processed further or used as an additive in other metal productions.
- Relatively slow production time
Although powder metallurgy involves quick processing times, it could take several hours for complete completion after the initial stages.
Processing time depends on the physical size of the product being produced.
- Lack of total uniformity
The presence of pores in PM leads to a larger amount of porosity in different parts of the product.
Because of unequal compression, the density of different sections of the finished product might vary in some situations.
Powder metallurgy FAQs
What is the powder metallurgy process?
Metal powder manufacturing provides a means for obtaining metals that have high purity of several elements. It is also used in compacting powders.
In contrast to other methods, it has the ability to produce particles on a microscale, which allows for very high purity levels even when large quantities are produced.
Powder metallurgy is a metal-forming technique that involves heating compressed metal powders to temperatures slightly below their melting points.
Powder metallurgy is a manufacturing technology that consists of three primary stages:
- The creation of metal powder
- The compaction and shape of the powder
- The consolidation and fusing of the powder into a solid metal component under high temperature and pressure.
Although the technique has been around for more than a century, it has only recently become generally acknowledged as a better method of creating high-quality parts for a wide range of critical applications.
This success may be attributed to the advantages the method has over conventional metal forming technologies like as forging and metal casting, such as material utilization, shape complexity, and near-net-shape dimensional control, among other things.
These, in turn, contribute to sustainability, establishing powder metallurgy as a green technology.
What are some applications of Powder metallurgy?
Powder metallurgy is used in many industries and fields of manufacturing.
It has been used for over 100 years in the aerospace industry, to create small metal parts that are stronger and lighter than normal.
As metal technology has advanced, powder metallurgy has not been limited to aerospace, but has expanded to health care, automotive, sports equipment, tools and mechanical devices.
Powder metallurgy can be combined with other processes such as turning or casting to make even larger parts.
Where is powder metallurgy used?
Powder metallurgy allows for the processing of materials with extremely high melting points, such as refractory metals like tungsten, molybdenum, and tantalum.
Such metals are extremely difficult to manufacture by melting and casting, and they are frequently highly brittle in the cast condition.
Why is powder metallurgy used?
Powder metallurgy has a number of benefits over other metalworking technologies. All of this adds up to increased product quality, shape and material flexibility, application diversity, and cost-effectiveness.
What is the scope of powder metallurgy?
Powder Metallurgy and Metal Ceramics addresses topics such as powder theory, manufacturing technology, and powder characteristics; forming process technology; sintering, heat treatment, and thermo-chemical treatment technology; sintered material properties; and testing techniques.
What is Sintering?
Sintering is the process of fusing particles together into a single solid mass using pressure and heat without melting the materials.
Metal, ceramic, plastic, and other materials are common particles that are sintered together.
What is the use of the sintering process in powder metallurgy
Sintering is used in powder metallurgy procedures to transform metal powders and other unique materials into end-use components.
Sintering is generally performed in a single, extended furnace with several temperature zones. Alloying materials or pressing lubricants may be added to the metal powder to assist the process.
What are some disadvantages of Powder metallurgy?
- Expensive tools and equipment are necessary for powder handling and manufacturing, as well as skilled personnel.
- Materials must be purified of all non-metallic inclusions; otherwise, contaminates can cause poor sintering results or other quality problems.
- Particles must be defect-free and free of any microscopic irregularities.
- Class equipment appropriate for production is needed since the process is typically performed in a furnace, not on an outdoor bench.
- More time-consuming than other processes, especially when large quantities of material are involved.
What products are made from powder metallurgy?
Powder Metallurgy uses in DIY power tools and home tools include bearings and other gear components.
Metal-graphite carbon brushes are also widely employed in electrical motors and generators used in household appliances, vehicles, and power equipment.