Question

A steel plate contains 0.82% C and the surface is going to be carburized. The carburization takes place such that the surface composition is 3.0% C, how long will it take to have 2.4% C at a depth of 0.55 mm into the plate at a temperature of 560 °C?

Table 5.2 A Tabulation of Diffusion Data Diffusing Species Qd(J/mol 87.400 148,000 се N 77,000 Ne 168,000 Fe Fe 251,000 284.000 200.000 Cud A1 144.000 Host Metal Do(m/s) Interstitial Diffusion Fe (a or BCC) 1.1 x 10-6 Fe (y or FCC) 2.3 x 10-5 Fe (a or BCC) 5.0 x 10-7 Fe y or FCC) 9.1 x 10-5 Self-Diffusion Fe (a or BCC) 2.8 x 10-4 Fe (y or FCC) 5.0 x 10-5 Cu (FCC) 2.5 x 10-5 A1 (FCC) 2.3 x 10-4 Mg(HCP) 1.5 x 10-4 Zn (HCP) 1.5 x 10-5 Mo (BCC) 1.8 x 10-4 Ni (FCC) 1.9 x 10+ Interdiffusion (Vacancy) Cu (FCC) 2.4 x 10-5 Zn (HCP) 2.1 x 10-4 A1 (FCC) 6.5 x 10-5 A1 (FCC) 1.2 x 10-4 Ni (FCC) 2.7 x 10-5 Cu (FCC) 1.9 x 10-4 Mg 136.000 Znº 94.000 461.000 Mod Nie 285,000 Znº 189.000 Cu 124.000 Cu 136.000 130.000 Mg Cu 256,000 Nie 230.000

Answer 1

given, 6 =0,82 % 0 = 3% x = 2.4 % x=0.55 mm T = 560 C = 833k At T = 56oc &- fe present BCC structure So, Using given data for diffusing species ac & Host Bet meta x Fe (BCC) Take Do=1. 1x 10 m2 Q = 87400 J/mol D = Doe Now, At T = 560 c= 833K, D = 1. 1x 10 x X e 87400 D = 3.636x 10 12 m/s using f( 22 ) + fich's and low of diffusion, s-to 1- eat a G-C6 2 Not 2.4-0.82 est a 3 - 0,82 2ND t 0,7 248 = 1 est 20 t est 20t Usiner erros function Table efees 0,2752 - 0,2277 0. 2763 - 0.2227 0.2752 2 - 0.20 0,20 0,2227 0,25-0,20 0,25 -0.2763 9 F 0.2752 z = 0.24890

x est(o. 249) = 0,2752= est/x ZNDE 0,249 - 0.55x103 Zoz 2/3.636 * 10 12 = 0, 249 urz = 579.19 t=335461. 6 sec :It = 93.18 hows & Answer Required time