(BMMP 1313) SULIT (c) Consider the gas carburizing of a gear of 1118 steel at 927C as illustrated in Figure Q2(c). The nominal carbon content of the steel gear before carburizing is 0.18 wt%. Diffusion coefficient, D (in y iron) at 927C is 1.28 x 1011 m/s. Assume the carbon content at the surface is 1.15 wt%. diffusing C atoms low C steel part Figure Q2(c): Carburizing a low carbon steel gear (i) State the purpose of gas-carburizing for steel parts. (ii) Explain gas-carburizing process for steel parts. [1 mark] [4 marks] (iii) Calculate the carbon content, in wt %, at 0.40 mm below the surface of the gear after a 5.0-h carburizing time. [5 marks] (iv) Calculate the time necessary, in hours, to increase the carbon content to 0.35 wt% at 1.00 mm below the surface of the gear. [5 marks]