Heating test without vacuum chamber:
The oven is built around an 2.5kW induction heater module from Aliexpress
2020-12-02 First sintering test
- 1210 °C target temperature
- low vacuum at 5-10mbar, no process gas
- PolyMIM 17-4PH feedstock, unmodified granules (not debindered)
- Heating cycle
- T+0min: Start: 15°C, 5mbar, cooling water temp 15 °C
- T+10min: Heating finished, 1210°C, 10mbar, cooling water temp 19 °C
- T+23min: Switched heating off, 1210°C, 8mbar, cooling water temp 25 °C
- T+33min: switched vacuum pump off, pressure stays at 4mbar
- ca T+53min: opening chamber, ca 250°C
Results:
red: unsintered granule, soft, can be scratched easily
green: sintered granule, hard, scratching just removes dark skin, shiny metal is revealed
- Granules are not completely sintered, only a skin of ca 0.5-1.0 mm
- Yet they are quite strong, they can not easily be cut using a wire cutter
Thermal imaging revealed several hot spots that need to be addressed:
Top of chamber reaches almost 200°C. Not a big issue, but putting a cap on the crucible probably would reduce the heat significantly
SSR get too hot. Needs heat spreader
Output side of power supply too hot. Needs further investigation. Bad cable connection?
Cable connecting induction module with copper pipe gets hot (right cable only). Bad connection, need something better
2021-09-09 Successful sintering
- 1350 °C target temperature
- low vacuum at 4*10⁻² mbar, no process gas
- PolyMIM 17-4PH feedstock, 3D Print (Bottle opener), debindered as per datasheet
- Part covered in sand-blasting media
- Heating cycle
- T+0 min: Start: 25°C, heated up to 600 °C and held, 4*10⁻² mbar
- T+60 min: heated up to 1350 °C, vacuum unchanged
- T+120 min: Switched heating off
- T+150 min: Switched vacuum pump off and opened chamber at ~200 °C
Results:
Part covered in sand blasting media, small but visible cracks (part not dried well, or heated too quickly?).
Wirewheeling revealed solid metal part with high detail conservation.
