Measurement of thermal diffusivity of ion nitrided steel by flash method

Abstract

Thermal diffusivity of diffusion layer of ion-nitrided steel is experimentally determined by flash method. In the experiment, a high intensity heat pulse is irradiated to the front surface of a nitrided thin disk-shaped metal, and the transient temperature rise of the opposite surface is recorded. The termal diffusivity of the sample material is then determined from the recorded temperature transient versus time curve. The heat diffusion equation for the flash diffusivity method is solved assuming onedimensional heat flow, homogeneous material and uniform absorbing of the heat pulse at the front surface of a sample, and using heat pulse function which describes the actual pulse shape. A photodiode detecting system is used to find the actual pluse shape. A capacitor discharge percussion welding is used to reduce the damage of the juction area at the surface. It is found that thermal diffusivity of diffusion layer of nitrided steel increases up to 10\% of that of non-nitrided steel.