1. Engineering Doctorate Lubricants Increase green density for given pressure and powder Decrease ejection force Reduce die wear Reduce density gradients Reduce flow rate Increase OR reduce green strength Decrease strength after sintering

2. Engineering Doctorate Sintering

3. Engineering Doctorate (Diagram) Figure 6.4: In the course of sintering (a) the compact acquires permanent strength while the volume shrinks (density increases) as a result of (b) elimination of most pores between particles.

4. Engineering Doctorate Sintering Temperature and Time for Various Metals MATERIALTEMPERATURE (°C)TIME (Min) Cooper, Brass and Bronze Iron and Iron-graphite Nickel Stainless Steels Alnico alloys (for permanent magnets) Ferrites Tungsten Carbide Molybdenum Tungsten Tantium 760 – 900 1000 – 1150 1100 – 1290 1200 – 1300 1200 – 1500 1430 – 1500 2050 2350 2400 10 – 45 8 – 45 30 – 45 30 – 60 120 – 150 10 – 600 20 – 30 120 480

5. Engineering Doctorate (Chart) Effect of the sintered density on the mechanical properties of powder compacts.

6. Engineering Doctorate (Chart) Effect of sintering time on density and strength of iron compacts.

7. Engineering Doctorate (Chart) Typical effects of powder particle size and compaction on density changes produced by sintering.

8. Engineering Doctorate (Chart) Typical effects of initial (green) density on density changes produced by sintering (course powder compacts).

9. Engineering Doctorate Liquid Phase Sintering  Low Tm powder component W-Cu (1100°C)  Low Tm product after diffusion WC-Co @ 1420°C  Pre-alloyed powder with supersolidus sintering

10. Engineering Doctorate Applications  Cemented carbide tools (WC-Co)  Fe-Cu or Fe-P  Cu-Sn, Fe-Cu, self-lub bearings  Alnico magnets  Dental Amalgams