Mechanical properties of strength-gradient steel sheets produced by solution nitriding

Solution nitriding and vacuum annealing treatments were applied to type 316L stainless steel plates in order to fabricate steel sheets that have a continuous strength change throughout their thickness direction. We produced three types of strength-gradient steel sheets through these treatments, with the hardness profile of each type of steel sheet reflective of the nitrogen concentration. The mechanical properties of the obtained steel sheets were investigated to demonstrate the effects of a strength gradient. As a result of tensile and bending tests, the uniaxial tensile deformation behavior of strength-gradient steel sheets is never affected by its strength gradient; however, it is governed by the average nitrogen content, while the bending deformation behavior of the sheets is significantly dependent upon the strength gradient through the thickness direction.