Metal Injection Molding Materials

Metals that can be atomised into a fine powder and sintered without contamination. Meco runs MIM-316L austenitic stainless, MIM-420 and MIM-440C martensitic stainless for hardened edges, MIM-17-4PH precipitation hardening stainless, MIM-4605 low alloy steel and MIM-FeNi50 soft magnetic alloy as core grades, plus cobalt and nickel bonded tungsten carbide, titanium, brass and bronze feedstock. Stainless dominates because it balances corrosion resistance, strength and clean sintering behaviour. Aluminum and zinc are not viable, since they melt below the temperature the process needs.

MIM-420 and MIM-440C, once heat treated. 440C carries more carbon and takes the higher hardness of the two, above 55 HRC against roughly 48 HRC for 420, at the cost of slightly more brittleness. Neither runs the corrosion resistance of 316L, since the chromium that gives edge-holding grades their hardness is partly tied up as carbides rather than free in the matrix. For a blade or wear tip that also has to shrug off moisture, 440C is usually the better trade than 316L pushed harder than it can go.

MIM-4605 quenched and tempered, at above 1600 MPa tensile and 48 HRC, but it buys that with elongation above 1 percent only. MIM-17-4PH aged to H900 gives above 1100 MPa with better ductility and stays stainless. If the part sees impact rather than steady load, the higher hardness option is usually the wrong one. Name the failure mode you are designing against and the grade choice narrows immediately.

Cobalt binder for general wear and cutting duty, nickel binder when the part sees acids, salts or moisture the cobalt would corrode out of. WC-6Co and WC-8Co, corresponding to ANSI grades C3 and C2, cover most cutting inserts and wear pads, with the lower cobalt content trading a little toughness for wear life. WC-6Ni and WC-8Ni swap that binder for nickel specifically for corrosive service, spray nozzles and chemical handling parts being the usual case, at a small cost in hardness and price.

Between 15 and 20 percent linearly during sintering, which is why the tool is cut 17 to 20 percent oversize. The exact figure belongs to the feedstock, the geometry, the gate position and how the part is supported in the furnace, so no single number applies to every job. We set the oversize from the qualified feedstock, then correct the steel off measured first articles. Long spans and uneven mass distribution are where shrinkage stops behaving predictably.

Around 0.3 to 0.5 percent of the nominal dimension straight from the furnace, so roughly 0.06 to 0.10 mm on a 20 mm feature. Surface finish comes off at 0.8 to 1.6 micrometres Ra as sintered. Where one dimension has to hold tighter than that, we mold near net shape and machine only that feature, which reaches ±0.01 mm. Marking those features on the drawing early keeps the rest of the part cheap.

Yes, and for three of the core grades it is the point. MIM-17-4PH is solution treated and aged to H900 or another approved condition, MIM-4605 responds to carburising or quench and temper like its wrought equivalent, and MIM-420 or MIM-440C are hardened the same way tool steel is. MIM-316L is not hardenable by heat treatment. Ageing, hardening and quenching all move dimensions, so parts with tight flatness or runout may need fixturing, sizing or final machining afterwards.

Close, but only with the right finishing. Chromium evaporates preferentially from the surface during sintering, and residual surface porosity holds contaminants, so an unfinished MIM stainless part can pit sooner than wrought. Polishing and passivation restore the surface chemistry and bring general corrosion performance back in line. For sterilised or chloride exposed parts, specify the finishing on the drawing rather than leaving it to the shop.

When the part is heavy, simple or low volume. Above roughly 100 grams debinding gets risky, and above 160 grams it usually fails. A simple turned or milled shape gains nothing from a mold. Below about 5,000 pieces a year the tooling will not amortise, so machining or metal 3D printing wins on total cost. Roughly one part in three brought to us for MIM gets quoted as machining or casting instead.

Yes. Powder lot certificates of analysis, EN 10204 3.1 material certificates, density and hardness records, first article inspection, CMM reports and PPAP packages are all available on request. REACH, RoHS and conflict minerals documentation is issued alongside them. Everything traces back to the powder lot and furnace batch that produced your shipment, under an IATF 16949:2016 quality system.