Mechanical and structural properties of AISI 1015 carbon steel nitrided after warm rolling

Abstract

Nitriding is usually applied to alloyed steels with the scope of increasing their surface hardness and wear resistance. Warm working has been found to produce a fine-grained microstructure, which makes possible further treatment of low carbon steels. In combination with a low temperature thermochemical treatment, such as nitriding, warm working can be used to produce machine parts with a though core and with a hard, wear resistant surface layer. This paper presents a study of mechanical and structural properties of AISI 1015 carbon steel nitrided after warm rolling. The rolling was performed in the following conditions: temperature 670–550°C, rolling speed 1.39 s-1 and deformation ratio 36.4%. After rolling, the samples were reheated to 550°C for a duration varying from a few minutes to 10 hours. The microstructural changes were assessed by light microscopy and quantitative microscopy analysis. Warm rolled samples were ion nitrided at 510–520°C in dissociated ammonia. The microstructure was analyzed by scanning electron microscopy and the mechanical properties were evaluated by tensile testing, surface hardness and friction coefficient measurements. Prior application of warm rolling makes possible (in the sense that is a viable solution) the ion nitriding of low carbon steels in order to produce machine parts with improved mechanical properties in the core (due to warm rolling) and longer service life (due to ion nitriding).