Metal injection molding VS Sintering

What is sintering in powder metallurgy? The term “powder metallurgy sintering” is frequently used to describe the process of heating metal powder or powder compact in a sintering furnace to a temperature below the melting point of the constituent parts. This is achieved through the interaction of particles, both physically and chemically, to give the material or product the necessary strength and properties after heat treatment. The primary step in powder metallurgy is sintering, which gives the material the necessary mechanical and physical characteristics. In several industries, including automotive parts and high-precision gear, powder metallurgy sintering is employed.

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What is the powder metallurgy process?

1. The powdered raw material preparation. Generally speaking, there are two types of milling techniques: physicochemical and mechanical. There are two types of mechanical methods: mechanical grinding and atomization method. The physical and chemical methods are further divided into vapor deposition, liquid deposition, electrolysis, chemical, reduction, and electrochemical corrosion methods. The three most popular techniques are electrolysis, atomization, and reduction.
2. Powder metallurgy molding to give the billet the required form. In order to create a compact with a specific size, shape, density, and strength, molding is implemented. There are two main categories of forming techniques: pressure forming and non-pressure forming. Die molding is the method most frequently employed in pressure molding. Furthermore, 3D printing technology can be utilized to create the embryo block.
3. The billet sintering process. One important procedure in powder metallurgy is sintering. To achieve the intended final mechanical and physical qualities, the molded compact is sintered. There are two types of sintering: unit system sintering and multi-component system sintering. When solid phase sintering unit systems and multicomponent systems, the sintering temperature is lower than the melting point of the metal and alloy utilized. In the context of multicomponent liquid phase sintering, the sintering temperature is often greater than the melting point of fusible components but lower than the melting point of refractory components. Apart from standard sintering, there exist other specialized sintering techniques such as hot pressing, melting, and loose sintering.
4. product post-processing. Numerous approaches can be used for the post-sintering treatment, depending on the specific needs of the final product. including electroplating, heat treatment, machining, finishing, and oil immersion. Furthermore, newer techniques like rolling and forging have been used recently to improve the quality of the materials processed by powder metallurgy following sintering.

Advantages and disadvantages of powder metallurgy processing technology

First, powder metallurgy process advantages:

1, Powder metallurgy can process special materials. Materials powder metallurgy methods can produce refractory metals as well as compounds, false alloys, and porous materials.

2, Powder metallurgy to save metal, and reduce costs. Because powder metallurgy can be pressed into the final size of the compact, there is no need to use machining. The loss of metal produced by this method is only 1-5%, while the general processing will lose 80% of the metal.

3，Make high-purity materials. The powder metallurgy process in the material production process does not melt the material, it will not be mixed with other substances bringing impurities, and sintering is carried out in a vacuum and reducing atmosphere, not afraid of oxidation will not have any pollution material. Therefore, the purity of the product is relatively high.

4, Material distribution is correct. The powder metallurgy method can ensure the accuracy and uniformity of the material composition in the ratio.

5, Mass production to reduce costs. Powder metallurgy is suitable for the production of a large number of products with uniform shapes, such as high-cost products such as gears, which can greatly reduce production costs.

Second, powder metallurgy process shortcomings:

1, Powder metallurgy product strength and toughness are poor. Due to the powder pressing of the compact, its internal pores can not be completely eliminated, therefore, powder metallurgy products in strength and toughness compared with the corresponding composition of castings, forging to be worse.

2, Powder metallurgy can not be made into large products. Since the fluidity of metal powder is worse than that of liquid metal, its shape and size will be limited to a certain extent, and its weight will not exceed 10 kilograms.

3, Powder metallurgy mold cost. Compared with the machining process that requires mold costs, it is a good choice for metal products with large quantities of demand.

How does MIM injection molding differ from PM press molding?

1: Infinite MIM injection molding

PM pressing is better suited for simpler structural pieces and is dependent on high-pressure uniaxial pressing. Geometric limitations are nearly nonexistent when using MIM injection molding, allowing for great creative freedom in three dimensions.

2: More economical MIM injection molding

Customers can gain savings on high-density, extremely complicated structural elements that cannot be created by any other standard process if they are willing to pay more for more expensive raw materials and equipment. Simple parts may be more affordably produced by PM pressing, but MIM injection molding can create precise part geometry without the need for cutting or secondary machining, saving manufacturing costs overall.

3: Powder material

The primary material difference between PM and MIM is particle size. Both methods employ the same basic powder and allow for the customization of specific parts. In comparison to PM-pressed molded powders, MIM injection molded particles are both significantly smaller and more costly.

4:Improved physical characteristics

In contrast to the structural parts generated by PM pressing molding, which have uneven sections due to friction between the tool and powder, the parts produced by MIM injection molding have consistent density throughout. In addition to having far higher strength, hardness, and wear resistance than PM, MIM injection molding has a much higher sintering temperature.

What products are more suitable for MIM injection molding?

Suitable Products for MIM

1. Small and Complex Components: MIM excels in creating intricate geometries that would be difficult or costly to manufacture using traditional methods. This includes parts with internal and external threads, miniaturized features, and complex 3D shapes.
2. Weight Range: MIM is ideal for parts weighing between 1 to 100 grams, although it can handle components up to 500 grams in some cases. The typical weight limit is around 200 grams, with an ideal range of 0.1 to 50 grams for optimal efficiency.
3. Material Versatility: MIM can utilize a variety of materials, including:
   • Stainless Steels: Such as 17-4 PH and 316L, known for their corrosion resistance and strength.
   • Tool Steels: Including high-performance options like D2 and M2.
   • Superalloys: Such as Inconel and Hastelloy, suitable for high-temperature applications.
   • Magnetic Alloys: For applications requiring specific electromagnetic properties.
4. High Dimensional Accuracy: MIM can achieve tight tolerances, typically around ±0.3% to ±0.5% of the nominal dimension, making it suitable for applications where precision is critical.

More Resources:

Powder metallurgy gear – Source: JHMIM