A method has been suggested to simulate the process of heat propagation for a pulsed surface source, using Fourier's equations. The following advantages of hardening by using a plasma thermal source with scanning are mentioned: the width of hardening area, the depth of hardening and the efficiency of the method are higher as compared to hardening, using a linearly moving source. Also high scanning frequencies give the opportunity to avoid the appearance of tempering areas and to modify a near-surface layer, in accordance with characteristics required.