Microstructural characterization of different metal matrix composite claddings reinforced by TiC through YAG laser cladding

Abstract

In this work, a YAG laser was used to clad TiC-reinforced metal matrix composite layers on the surface of different types of metals; low carbon steel, high C–Cr bearing tool steel, spheroidal graphite cast iron and commercially pure titanium. The cladding processes were carried out at heat inputs ranging from 175 J mm−1 to 700 J mm−1 and at a fixed traveling speed of 4 mm s−1. The microstructures of the cladding layers were investigated in detail. In all cases, TiC-surface metal matrix composite layers were successfully formed at different laser heat inputs on all the metal surfaces. A few TiC particles seemed as fine dendrites after the laser treatment. The amount of dendritic TiC has a direct relationship with the laser heat input. For low carbon steel, the clad layer showed a martensitic structure, with sound metallurgical bonding to the base metal and without any defects at the highest laser heat input used in this study (700 J mm−1). In the case of high C–Cr bearing tool steel, lower laser heat inputs were enough to form a sound clad layer consisting of fine TiC dendrites distributed in a matrix of martensite laths, some retained austenite and acicular carbides. Laser heat input of 175 J mm−1 was enough to build a defect-free clad layer on spheroidal graphite cast iron. The matrix comprised of cementite, martensite, and some blocks of retained austenite. Cracking appears at a higher heat input of 500 J mm−1 in the spheroidal graphite cast iron. The matrix of the clad layer on pure Ti substrate was α′-Ti martensite, which decreased by increasing the laser heat input.