Microstructure of Fe–TiC Composite Surface Layer on Carbon Steel Formed by Laser Alloying Process

Abstract

Laser alloying using a carbon steel substrate pre-coated powder mixture of pure titanium and graphite was carried out to form an Fe–TiC composite surface layer for improving wear resistance. The microstructure of the composite layer was studied in detail using OM, SEM, XRD and STEM to reveal the effect of the laser alloying conditions on the distribution of carbides. Coarse particles (1–5 µm) and submicron particles of TiC were observed. TiC particles were distributed in a lath martensite matrix, and the area fraction of TiC was about 8 to 25%. The area fraction and size of TiC depended on the laser scanning speed. Under the condition of a high scanning speed, a composite layer with a high area fraction and a coarser size of TiC was obtained. These composite layers exhibit high hardness and superior wear resistance compared with a laser transformation hardened area of the same substrate.