Growth mechanism of in situ Ti(C_yN_1-y) particles in laser deposited coating

A new in-situ synthesis method was used to prepare the composite coating reinforced by Ti(C_yN_1-y) particles through CO₂ laser cladding technology. Scanning electron microscope (SEM) and electron probe microscopy analyzer (EPMA) were used to analyze the phases in the composite coating. The results show that Ti(C_yN_1-y) particles are formed by an in-situ metallurgical reaction of TiN particle and graphite powder during laser cladding process. The nucleation and growth mechanism of the formation of Ti(C,N) particles have close relationship with the original titanium nitride (TiN). When the size of the original titanium nitride particles is small (< 5 μm),a great deal of energy absorbed by the cladding material may cause the dissolution of the original titanium nitride (TiN) particles to form the titanium carbonitride Ti(C_yN_1-y) particles,whose shapes are rhombus. If the size of original titanium nitride particles is big (> 5 μm),energy absorbed by the cladding material is limited,so it only causes the outer marginal dissolution of the original titanium nitride (TiN) particles. Finally,the annular structure ceramic particles named titanium carbonitride Ti(C_yN_1-y) are synthesized by a solid-solution metallurgical reaction in the laser cladding process.