If you look at MIM material lists, 316L is everywhere. 304 is noticeably rarer. Why?
The short answer: 304 is difficult to MIM because its higher carbon content (0.08% max vs 0.03% max for 316L) makes it prone to sensitization during the slow cooling phase of sintering. 316L's molybdenum content and lower carbon make it far more forgiving in the MIM process. MIM 304 vs 316L — key differences:| Property | MIM 304 | MIM 316L | Why It Matters |
|---|---|---|---|
| Carbon content | 0.08% max | 0.03% max | 304 risks chromium carbide precipitation during slow sintering cool-down |
| Molybdenum | 0% | 2-3% | 316L has superior chloride corrosion resistance |
| Typical sintered density | 94-96% | 96-98% | 304 densifies less completely under standard MIM sintering cycles |
| Sintering temperature | 1300-1350°C | 1320-1380°C | 316L is more forgiving with a wider sintering window |
| Corrosion resistance (post-MIM) | Good, but risk of intergranular corrosion | Excellent — low carbon + Mo prevents sensitization | 304 may fail salt spray tests after MIM processing |
| Relative powder cost | 0.9x | 1.0x (baseline) | 304 is slightly cheaper but the cost difference is small |
303 contains sulfur (0.15% min) which makes it excellent for CNC machining but problematic for MIM — the sulfur forms low-melting-point sulfides during sintering, causing hot shortness and embrittlement. 303 is not recommended for MIM.
Quick Q: Is 304 stainless good for MIM?304 is technically MIM-processable but rarely recommended. 316L produces better density, more consistent corrosion resistance, and a wider processing window — for a minimal cost premium. Stick with 316L for MIM and save 304 for wrought or machined applications where its limitations don't apply.
For applications where 304 is specified by tradition rather than engineering requirement, 316L is a drop-in replacement with superior performance at fractionally higher cost.