Question

Determine the carburizing time necessary to achieve a carbon concentration of 0.50 wt% at a position 3.3 mm into an iron-carbon alloy that initially contains 0.18 wt% C. The surface concentration is to be maintained at 1.1 wt% C, and the treatment is to be conducted at 1050°C. Assume that D0 = 3.1 × 10-5 m2/s and Qd = 120 kJ/mol. The following table may be useful.

An iron-carbon alloy initially containing 0.227 wt% C is exposed to an oxygen-rich and virtually carbon-free atmosphere at 1080°C. Under these circumstances the carbon diffuses from the alloy and reacts at the surface with the oxygen in the atmosphere; that is, the carbon concentration at the surface position is maintained essentially at 0.0 wt% C. At what position will the carbon concentration be 0.170 wt% after a 9 h treatment? The value of D at 1080°C is 1.9 × 10^-10 m²/s.

Nitrogen from a gaseous phase is to be diffused into pure iron at 700°C. If the surface concentration is maintained at 0.19 wt% N, what will be the concentration (in weight percent) 2.3 mm from the surface after 7.5 h? The diffusion coefficient for nitrogen in iron at 700°C is 1.2 × 10^-10 m²/s.

z		erf(z)		z		erf(z)		z		erf(z)
0.00		0.0000		0.55		0.5633		1.3		0.9340
0.025		0.0282		0.60		0.6039		1.4		0.9523
0.05		0.0564		0.65		0.6420		1.5		0.9661
0.10		0.1125		0.70		0.6778		1.6		0.9763
0.15		0.1680		0.75		0.7112		1.7		0.9838
0.20		0.2227		0.80		0.7421		1.8		0.9891
0.25		0.2763		0.85		0.7707		1.9		0.9928
0.30		0.3286		0.90		0.7970		2.0		0.9953
0.35		0.3794		0.95		0.8209		2.2		0.9981
0.40		0.4284		1.0		0.8427		2.4		0.9993
0.45		0.4755		1.1		0.8802		2.6		0.9998
0.50		0.5205		1.2		0.9103		2.8		0.9999

Answer 1