1. Introduction: The Core Role of Stainless Steel in the MIM Field​

The core definition of “stainless steel” lies in its excellent corrosion resistance and discoloration resistance. As one of the earliest materials to be industrially applied in MIM (Metal Injection Moulding), the importance of stainless steel in this field is self-evident — in regions with mature MIM technology such as Japan and Europe, more than 50% of MIM components are made of stainless steel, which fully confirms the supporting value of stainless steel for the MIM industry in terms of production scale.​

2. Core Characteristics and Classification Basis of Stainless Steel​

Stainless steel belongs to the iron-carbon alloy family, and its most critical advantage is that: compared with other iron-carbon alloys, stainless steel has significantly better corrosion resistance and oxidation resistance. The root cause of this characteristic is that the chromium (Cr) content in its alloy composition is not less than 12% (by mass) — chromium forms a stable oxide film on the material surface, thereby effectively resisting corrosion.​

According to the differences in microstructure, stainless steel can be divided into three core categories, each corresponding to different performance characteristics and application scenarios. The specific classifications and representative grades are as follows:​

(1) Austenitic Stainless Steels​

Austenitic stainless steels have good toughness, ductility and weldability, and are suitable for scenarios requiring high corrosion resistance and processability. Common grades and their characteristics are:​

303, 303.1Se: Sulfur (S) is added to improve machinability, while carbon content is reduced; special customized grades are available to meet high-precision machining requirements.​

304, 304.1Se: General-purpose austenitic stainless steels with high cost-effectiveness, widely used in conventional corrosion-resistant scenarios; derivative grades with reduced carbon content and special grades for specific scenarios are available.​

316, 316.1Se: Molybdenum (Mo) is added to significantly improve corrosion resistance, especially in seawater, acid and alkali environments; low-carbon grades suitable for welding scenarios and special customized grades are available.​

317L, 314: 317L is a low-carbon grade suitable for welding scenarios below 1100°C; 314 enhances high-temperature resistance by increasing silicon (Si) content, and at the same time increases chromium and nickel (Ni) content to further improve heat resistance temperature, making it suitable for high-temperature working conditions.​

(2) Martensitic Stainless Steels​

Martensitic stainless steels can achieve hardness adjustment through heat treatment, have high strength, and are suitable for scenarios requiring strength and wear resistance. Common grades and their characteristics are:​

410, 410L: 410 is a general-purpose martensitic stainless steel, balancing strength and basic corrosion resistance; 410L is a low-carbon derivative grade, which reduces the risk of welding cracks and improves toughness.​

420: A high-carbon martensitic stainless steel that can obtain higher hardness and wear resistance after heat treatment, suitable for precision components requiring wear resistance.​

(3) Ferritic Stainless Steels​

Ferritic stainless steels have good corrosion resistance and thermal conductivity, and cannot be hardened by heat treatment, making them suitable for cost-sensitive scenarios requiring stable corrosion resistance. Common grades and their characteristics are:​

430: The most widely used non-hardening ferritic stainless steel, including low-carbon derivative grades; high-stability grades are also available, which can maintain the ferritic structure in the full temperature range and avoid performance impact caused by phase transformation.​

430Ti, 434, 444: 430Ti improves corrosion resistance by adding titanium (Ti); 434 is a low-carbon ferritic stainless steel that improves weldability; 444 is a high-stability grade that maintains the ferritic structure in the full temperature range, suitable for complex working conditions.​

(4) Other Special-Grade Stainless Steels​

440 Series: Belongs to the category with the highest carbon content in the 400-series stainless steels. After heat treatment, it can obtain extremely high hardness and wear resistance, suitable for scenarios requiring extreme wear resistance (such as precision bearings and tool components).​

3. Core Advantages of Stainless Steel Powder in MIM Process​

Using stainless steel powder for MIM forming can give full play to the synergistic advantages of the process and materials. The core advantages are reflected in the following four aspects:​

1. Design Flexibility (FLEXIBILITY)​

It breaks the limitations of traditional processing technologies and can freely form small-sized but complex-structured precision components (such as micro-components in medical equipment and precision sensor components in automobiles) without a large amount of subsequent secondary processing, greatly simplifying the production process.​

2. High Dimensional Accuracy (HIGH TOLERANCE)​

The formed components can achieve high dimensional tolerances, effectively reducing dimensional deviations, lowering subsequent correction costs, and meeting the strict requirements for dimensional accuracy in precision manufacturing fields (such as aerospace and medical care).​

3. Excellent Toughness (TOUGHNESS)​

In terms of mechanical properties, MIM-formed stainless steel components have similar properties to wrought stainless steel grades, especially in terms of toughness and impact resistance, and can replace traditional wrought parts in scenarios with complex stress conditions.​

4. Near-Full Density (HIGH DENSITY)​

It can produce stainless steel products with near-full density, effectively reducing internal pores in the material, improving the strength, corrosion resistance and service life of components, and avoiding performance shortcomings caused by insufficient density.​

4. Main Application Fields​

Relying on the above advantages, stainless steel powder is widely used in the following high-demand fields:​

Medical Field (MEDICAL): Used to manufacture implantable medical device components (such as artificial joint accessories) and precision surgical instruments, which need to meet the requirements of biocompatibility, resistance to body fluid corrosion and high dimensional accuracy.​