1. In physics the truth is rarely perfectly clear, and that is certainly the case with human affairs. Hence, what is not surrounded by uncertainty cannot be the truth
– Richard Feynman

2. Speaking of tools…
OK, then, what about "ceramic" tools?
Most from Al2O3 - pressed to near-net shape & sintered at ° C - ground on diamond wheels
At high temps, high hardness, wear resistance
Can use for mat'ls w/ up to RC66
Very brittle
Cost ≈ 2X that of carbide tools

3. Grey - C as graphite flakes Ductile (nodular) - C as graphite nodules
Cast irons
Types
White - C is all in CM
Grey - C as graphite flakes
Ductile (nodular) - C as graphite nodules

4. Cast irons

5. very brittle, wear resistant, not machinable, limited use
Cast irons
White - C is all in CM
very brittle, wear resistant,
not machinable, limited use
Grey - C as graphite ("corn") flakes
Si added to graphitize,
brittle cuz of flake stress
raisers - cheap, widely
used, vibration damping
Ductile (nodular) - C as graphite
nodules "inoculated" w/
Mg or Ce to get nodules
- up to 40% EL

6. Case hardening
Gear tooth
Carburizing - pack & gas - add C from CO gas
Nitriding - add N from NH3
Case must be Q & T, except for nitrided
Carbonitriding - add C & N from CO & NH3

7. Case hardening
Alternate case hardening method
Induction hardening - surface heating by high-frequency AC, then Q & T

8. Truck rear axle shaft
Ford uses SAE 1050 steel with manganese content modified from 0.80 to 1.10% in rear axle shafts.
Normally Mn
YS = 49 ksi, TS = 90 ksi, EL = 15% (hot-rolled)
YS = 80 ksi, TS = 120 ksi (Q+T) depends on
heat treat conditions

9. Jominy test
Specimen & water quench
Hardness measurement

10. Jominy test

11. Quench severities

12. Assignment:
Review today's classnotes
a. cast irons
b. case hardening
c. Jominy test
d. Jominy curves
e. quench severities
Read in text:
pp , ,
see photos on pp. 91, 446