Material selection drives more outcomes in a metal injection molding program than almost any other choice. The grade defines corrosion behaviour, mechanical strength, magnetic response, achievable tolerances, finishing options, and cost. Choosing the right family early saves tooling iterations and prevents the most common RFQ mistakes we see at the drawing-review stage.
This guide walks through the material families SINTS runs most often for OEM programs, with the property and process notes our engineering team uses when reviewing customer drawings. It is written for sourcing teams, design engineers, and program managers who need to set a direction before going to RFQ.
Why material choice drives the whole program
In MIM, material choice sits upstream of geometry, tolerance and surface finish. The selected powder affects feedstock rheology (how the mix flows into the mold), debinding behavior, sintering shrinkage and the achievable density. Different families also need different sintering atmospheres: stainless can be sintered in vacuum or partial-pressure hydrogen, while soft-magnetic and tungsten grades often need hydrogen or argon to keep carbon and oxygen under control.
The practical effect is that a part designed for 316L may not simply be re-cut for 17-4PH or titanium. Shrinkage changes, tooling may need to be re-cut, and post-sinter operations (such as heat treatment or machining) shift. Deciding the material family early avoids multiple tooling iterations.
Start from the application, not the grade
Start by defining the function the material must deliver: corrosion resistance, strength, wear resistance, magnetic response, low mass, high mass, thermal/electrical behavior, appearance or a customer-mandated specification. That functional requirement determines which material family deserves review.
- Corrosion resistance: stainless grades such as 304, 316/316L and 17-4PH may be considered depending on strength and environment.
- Strength and wear: 4140, MIM 4605, martensitic stainless and heat-treatment options can be evaluated.
- Soft-magnetic response: FeSi 3.0 is included in current SINTS material data; other magnetic grades are confirmed by project.
- Lightweight / specialty projects: titanium- and aluminum-alloy components can be manufactured by SINTS, with the route selected from MIM, PM, CNC or a hybrid process as appropriate.
- High-density or copper-family projects: tungsten/tungsten-alloy and copper/copper-alloy components can also be evaluated, with exact grade and manufacturing route confirmed from the drawing and required properties.
If the customer specification already fixes the grade, the engineering review shifts to geometry, process route, heat treatment, surface condition and inspection.
Stainless steels — the workhorse family
The current SINTS material sheet documents MIM stainless grades including 316L, 316, 304, 440C, 420/410 and 17-4PH. Their final properties depend on grade, sintered or heat-treated condition, density and the project specification.
Do not select a stainless grade only from an application label such as “medical,” “food” or “outdoor.” Corrosion environment, cleaning chemistry, contact conditions, strength, hardness and required documentation should be confirmed for the actual program.
Low-alloy and structural steels — cost-effective strength
The current SINTS material sheet documents MIM 4605 (Fe-2Ni) and MIM 4140 in sintered and heat-treated conditions. These grades are useful when strength, hardness or wear requirements point away from austenitic stainless.
Low-alloy steels generally require a deliberate corrosion-protection strategy when the service environment demands it. Coating, plating, black oxide or another finish should be selected from the actual exposure and dimensional requirements rather than added as a generic afterthought.
Soft-magnetic alloys — for sensor and solenoid parts
Soft-magnetic components are selected primarily for magnetic performance rather than only for strength or corrosion resistance. Current SINTS material data includes FeSi 3.0 for relevant magnetic applications.
Other soft-magnetic grades may be possible, but permeability, coercivity, saturation behavior, carbon control, heat treatment and final inspection requirements should be confirmed for the specific project rather than assumed from a generic material family.
For solenoids and magnetic assemblies, the material decision should be reviewed together with air gap, sliding surface, corrosion protection, operating temperature and any required secondary machining.
Project-capable materials: titanium, aluminum, tungsten & copper
SINTS can manufacture components in titanium alloys, aluminum alloys, tungsten/tungsten alloys and copper/copper alloys. These are treated as project-capable material families rather than as one universal standard MIM offering.
The correct process route depends on the exact grade, geometry, part size, annual demand, required density or conductivity, surface condition and validation requirements. Depending on the part, the most suitable route may be MIM, powder metallurgy, CNC machining or a hybrid process.
For these material families, send the drawing together with the required grade or functional property. SINTS will confirm the manufacturing route and any material-specific validation before quotation.
SINTS material reference data
Current SINTS material data includes established MIM grades such as 4605, 4140, 316L, 316, 304, 440C, 420/410, 17-4PH, HK30 and FeSi 3.0, together with a PM material reference for FD-05N2C-360.
Define mechanical properties, density, hardness and magnetic requirements using the applicable drawing, material specification and SINTS material data sheet.
Titanium, aluminum, tungsten and copper families are also within SINTS manufacturing capability, but the exact alloy, process route and achievable properties are confirmed during project review.
See the current Materials & Alloy Guide for material grades, properties and project requirements.
How material affects sintering, shrinkage and tolerances
Material choice changes feedstock behavior, thermal processing, shrinkage, distortion risk, heat treatment and the way critical dimensions are controlled. There is no single shrinkage or tolerance value that should be applied to every MIM alloy and geometry.
Tooling compensation is established from the selected feedstock, part geometry and trial results. Critical dimensions are then reviewed to decide whether they can remain as-sintered or require sizing, machining, grinding or another secondary operation.
For project-capable materials such as titanium, aluminum, tungsten and copper, the process route may differ from standard stainless or low-alloy MIM, so material and manufacturing-route selection should be completed together.
How to specify material in your RFQ
The clearest RFQ always names the material by UNS or AISI designation, the heat-treatment condition, and the property or certificate requirements. Vague specifications such as “stainless steel” or “magnetic grade” force the supplier to guess and slow the quotation.
- Name the grade: Use UNS (S31603 for 316L, S17400 for 17-4PH, R56400 for Ti-6Al-4V) or AISI designation. Avoid trade names.
- State the heat-treatment condition: Annealed, sintered only, solution-treated and aged, H900 / H1025 / H1100 for 17-4PH.
- List required properties: Tensile strength, yield, elongation, hardness, density, magnetic permeability if relevant.
- Specify finish and protection: As-sintered, tumbled, polished, passivated, plated, PVD-coated, etc.
- Note certification needs: Material certificate (EN 10204 3.1), FAI report, dimensional report, RoHS or REACH statements if the end market needs them.
When SINTS helps you decide
The material choice almost always affects the part geometry, the sintering profile and the inspection plan. For OEM programs with first-time MIM use, the most valuable step is to send the drawing and a short application note before locking the spec. SINTS engineering reviews the drawing against the chosen family, confirms achievable tolerances and density, and proposes the most cost-effective combination of family, finish and inspection.
For programs where the material is already locked (because of regulatory, biocompatibility or end-use requirements), the review focuses on geometry and finish. Either way, the earlier the supplier is in the loop, the fewer iterations are needed on the way to stable production.
Related Component Families
Use these component-family pages to move from general process guidance to drawing-specific DFM questions.
Precision Small Metal Components
Material choice changes corrosion, strength, wear, appearance and secondary-processing decisions on compact precision parts.
Component guide →Fluid-Control & Dispensing Components
Media compatibility, magnetic behavior, corrosion and surface condition can dominate the grade choice.
Component guide →Cutting & Wear Components
Hardness, edge/contact wear and heat-treatment response are central material-selection inputs.
Component guide →Mechanism Components
Links, levers, pawls and cams need material selection tied to load, fatigue, impact and contact wear.
Component guide →Custom OEM Metal Components
For unusual alloys or performance requirements, the exact grade and route are confirmed project by project.
Component guide →Need help choosing a material?
Send your drawing and a short application note. SINTS engineering reviews the proposed material family, critical tolerances and density requirements before confirming the manufacturing route.
Send Drawing for Review