Guangming Group: An Introduction to the Forming Technology of Powder Metallurgy

Complete Principles & Processes of Powder Metallurgy Forming

Powder metallurgy mainly includes three mainstream forming technologies with completely‑different principles: conventional cold‑press sintering (PM), Metal Injection Molding (MIM) and isostatic pressing.

1. Conventional Powder Metallurgy‑Die Compaction (Most‑Common PM Process)

Applications: Gears, bushings, gaskets and oil‑impregnated bearings.

Full Forming Process

1. Powder Mixing & Batching

Metal powders (iron, copper, stainless‑steel powder) are fully blended with a small amount of lubricant and binder.

2. Powder Loading

The mixed powder is poured into the cavity of a steel die (consisting of die sleeve, upper punch and lower punch).

3. Compaction (Core Forming Step)

Pressure of 200‑700 MPa is applied by a hydraulic press. The upper and lower punches squeeze the powder particles to get close and interlock with one another, compacting into a semi‑finished solid part known as a green compact

Green compact: Parts are only pressed together with extremely low strength and prone to breakage upon impact.

Limitation: The die can only open and close vertically. Side undercuts, deep grooves and complex curved structures cannot be produced.

4. Ejection

The lower punch pushes the compacted green compact out of the die. The forming procedure is finished and the workpiece is transferred for sintering.

5. Sintering (Consolidation, not part of forming yet indispensable)

Workpieces are heated in a protective‑atmosphere furnace at a temperature below the melting point of the metal. Powder particles bond together through sintering to endow the component with mechanical strength.

Schematic forming flow: Powder → High‑pressure compaction → Green compact → Sintering → Finished part

2. MIM‑Metal Injection Molding (High‑end Powder‑Metallurgy Process, Widely Used for Medical Latches & Hinges)

Applications: Small‑sized complex 3D special‑shaped components, such as quick‑release locking blocks and shaft eccentric parts for defibrillator arm brackets.

Its forming principle is nearly identical to plastic injection molding.

Forming Procedures

1. Feedstock Preparation

Ultra‑fine metal powder is compounded with polymer binders (paraffin wax, plastics) via high‑temperature kneading. The mixture is extruded and pelletized to produce MIM feedstock granules similar to plastic pellets.

2. Injection Molding (Core Forming Operation)

Feedstock pellets are fed into an injection‑molding machine, heated and melted, then injected at high pressure into a sealed steel mold. After cooling, an injection‑molded green compact with the identical appearance of a plastic component is removed.

✅ Advantages: It can fabricate complex geometries that cannot be achieved by cold compaction, including undercuts, curved surfaces, thin walls, irregular profiles and porous structures.

3. Debinding

All polymer binders are removed from the green compact, leaving a pure‑metal skeleton (brown part).

4. High‑temperature Sintering

Parts are heated inside a vacuum sintering furnace. The component shrinks by 15‑20 % in overall dimension and turns into a high‑density metal workpiece.

3. Cold Isostatic Pressing (CIP)

1. Load metal powder into a flexible rubber mold;

2. Place the mold inside a high‑pressure water/oil pressure vessel for simultaneous uniform pressurization from all directions;

3. Produce large‑size green compacts with even density distribution.

It is mostly adopted for large‑scale workpieces, cemented carbides and sputtering targets. Due to high mold costs, this process is rarely used for small‑batch‑production components.

4. Hot Isostatic Pressing (HIP)

Components are subjected to high‑pressure compression from all directions while being heated at high temperature.

Commonly applied to aerospace superalloy and titanium‑alloy parts to eliminate internal pores and achieve near‑100 % density.

Keywords: Powder Metallurgy, Metal Injection Molding, Powder‑Metallurgy Gears

Guangming Group

Guangming Group specializes in the R&D and manufacturing of metal‑forming technologies and wear‑resistant materials. Our core products cover powder‑metallurgy components manufactured by metal compaction forming and metal injection molding.

Our company boasts a high‑caliber talent team. The founding team originates from Guangdong Institute of Nonferrous Metals, a research institute directly affiliated to a former national‑level ministry. With rich industrial experience and strong R&D capability, our team delivers continuous innovation momentum for enterprise development.

The group has obtained 5 invention patents and more than 30 utility‑model patents. It has been certified to IATF16949, ISO9001‑2015 Quality‑Management System, ISO14001 Environmental‑Management System and Intellectual‑Property‑Management System, together with international trademark certification.

We are recognized as an Innovative Enterprise of Guangdong Province, a Little‑Giant Science and Technology Enterprise of Guangzhou, a director‑unit of Guangdong Powder‑Metallurgy Industry‑Technology Innovation Alliance, and one of the initiators of Guangzhou Advanced Powder‑Metallurgy Cluster Promotion Center.