Introduction
Metal powder injection moulding (MIM) is an emerging technology that has revolutionized the industrial sector in recent years by providing a means of producing intricate parts with complex geometries at relatively high production rates. MIM combines the best of powder metallurgy with the accuracy and repeatability of precision injection moulding. This technology is widely used in the production of various structural and functional components including medical implants and aerospace parts.
The traditional metal powder injection moulding processes uses nickel or cobalt based powders to produce components of high strength and dimensional accuracy. However, the cost of such powders is high and the high-cost of production makes the part cost prohibitive. Thus, there is a need to find alternative powders that can be used in metal powder injection moulding processes to produce parts of high strength at lower cost.
In this article, we discuss the use of iron powder in metal powder injection moulding (MIM) processes and compare it with the use of nickel and cobalt-based powders. We also discuss the advantages and disadvantages of using iron powder over the more traditional metals in the injection moulding process.
Advantages of Iron Powder in MIM Processes
The use of iron powder in metal powder injection moulding gives several advantages over the use of nickel and cobalt-based powders. This is primarily due to its wide availability, low cost and high strength characteristics.
Firstly, iron powder has a lower cost compared to cobalt and nickel powders. This makes it suitable for large scale production processes. Secondly, iron powder is widely available and is easily sourced from various suppliers.
Thirdly, iron powder provides a good mix of strength, ductility and wear resistance properties, which makes it suitable for producing components requiring these properties. In addition, it exhibits good thermal and electrical conductivity, making it a suitable choice for producing complex geometries.
Finally, iron powder can be used to produce components requiring higher levels of strength. This is mainly due to the metal’s propensity to develop a micro-structure of Fe3C (carbide) which gives a tensile strength of up to 900 MPa, which is much higher than that of cobalt and nickel.
Disadvantages of Iron Powder in MIM Processes
Despite the numerous advantages that iron powder provides, there are also some drawbacks associated with its use in metal powder injection moulding. Firstly, iron powder requires a longer sintering time compared to nickel and cobalt-based powders. This is primarily an issue when producing components of large size and/or complex geometry, as the longer sintering time is reflected in increased processing time and cost.
Secondly, iron powder has a lower thermal stability compared to cobalt and nickel-based powders. This significantly affects the accuracy of the component and its dimensional tolerance during the injection moulding process.
Finally, iron powder requires injecting pressure up to 125 MPa in order to obtain a uniform part. This is higher than the pressure required for other metal powders, meaning that additional mechanical components may be necessary for successful processing.
Conclusion
In summary, the use of iron powder for metal powder injection moulding can provide a low-cost alternative to cobalt and nickel-based powders. However, the added complexity associated with the longer sintering time, lower thermal stability and higher injection pressure means that there are trade-offs to consider when selecting a powder for MIM processes.
