Features of Behavior of Persian Damascus Steel of Xviii Century and Contemporary Damascus Steel With Cyclic Loading

It is shown that the ancient Damascus structure of a Persian blade differs in composition and nature of the separation of layers from the multilayer structure of contemporary welding Damascus steel. Structural analysis of the step-by-step transformation of the cellular distribution of excess carbides within separate layered conglomerates, represented by a genuine Damascus troostite-carbide structure (65/35), has been performed on Damascus steel. In specimens of contemporary welding Damascus steel a stepwise process has been performed for transformation of ferrite-pearlite (40/60) structures into ferrite-martensite (30/70) structures. Continuous ferritic layers are transformed into accumulations of isolated recrystallized ferritic grains. Values of threshold stress intensity coefficient (∆K_th) are determined graphically, with which a fatigue crack does not propagate over the extent of a prescribed number of cycles. A critical value is recorded for stress intensity coefficient (∆K_fc) with which knife blades are broken. Behavior of a kinetic diagram linear section of the kinetic fatigue failure diagram (KFFD) is evaluated. In welding Damascus steel over a linear section areas of delayed fatigue crack growth are observed due to local delamination ahead of its front.