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(a) A carburising treatment is to be carried out on a component made from a steel with initial concentration of 0.1wt% carbon, by exposing the surface to a carbon rich atmosphere at a temperature of 1025°C. The diffusion coefficient may be calculated using the following equation: -Qa` D = Do exp Where R is the gas constant (8.31Jmol1K-1), Tis the absolute temperature (K) and Do (m2s-1) and Qd (Jmol-1) are the pre-exponential term and activation energy for diffusion respectively.

(a) A carburising treatment is to be carried out on a component made from a steel with initial concentration of 0.1wt% carbon, by exposing the surface to a carbon rich atmosphere at a temperature of 1025°C. The diffusion coefficient may be calculated using the following equation: -Qa` D = Do exp Where R is the gas constant (8.31Jmol1K-1), Tis the absolute temperature (K) and Do (m2s-1) and Qd (Jmol-1) are the pre-exponential term and activation energy for diffusion respectively.

Introduction to Chemical Engineering Thermodynamics
Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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(a) A carburising treatment is to be carried out on a component made from a steel with initial concentration of 0.1wt% carbon, by exposing the surface to a carbon rich atmosphere at a temperature of 1025°C. The diffusion coefficient may be calculated using the following equation: -Qd` D = Do exp RT Where R is the gas constant (8.31Jmol-1K1), Tis the absolute temperature (K) and Do (m2s-1) and Qd (Jmol-1) are the pre-exponential term and activation energy for diffusion respectively. Using suitable values for Do and Qd from Table Q3.1, show that the value of the diffusion coefficient for carbon in this steel at 1025°C is 2.53x10-11 m2s-1. ark (b) The carbon rich atmosphere may be considered to raise the surface concentration instantaneously to 1.0wt% carbon, and maintains it constant at that level. The non-steady state diffusion equation is as follows: Cx - Co 1– erf ) Cs - Co Where Cx is the concentration at position x (m) after time t (s), Co is the initial concentration, Cs is the surface concentration and D is the diffusion coefficient (m²s-1). For this steel with initial carbon content (Co) of 0.1wt% carbon, calculate the time required to obtain a carbon concentration (Cx) of 0.6wt% carbon at a depth of 0.4mm below the surface. Express your answer in hours.
Transcribed Image Text:(a) A carburising treatment is to be carried out on a component made from a steel with initial concentration of 0.1wt% carbon, by exposing the surface to a carbon rich atmosphere at a temperature of 1025°C. The diffusion coefficient may be calculated using the following equation: -Qd` D = Do exp RT Where R is the gas constant (8.31Jmol-1K1), Tis the absolute temperature (K) and Do (m2s-1) and Qd (Jmol-1) are the pre-exponential term and activation energy for diffusion respectively. Using suitable values for Do and Qd from Table Q3.1, show that the value of the diffusion coefficient for carbon in this steel at 1025°C is 2.53x10-11 m2s-1. ark (b) The carbon rich atmosphere may be considered to raise the surface concentration instantaneously to 1.0wt% carbon, and maintains it constant at that level. The non-steady state diffusion equation is as follows: Cx - Co 1– erf ) Cs - Co Where Cx is the concentration at position x (m) after time t (s), Co is the initial concentration, Cs is the surface concentration and D is the diffusion coefficient (m²s-1). For this steel with initial carbon content (Co) of 0.1wt% carbon, calculate the time required to obtain a carbon concentration (Cx) of 0.6wt% carbon at a depth of 0.4mm below the surface. Express your answer in hours.
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