Cracking behavior and control of plasma clad high chromium iron based composite coating

Fe-Cr-C and Fe-Cr-C-Ti composite powder was prepared by precursor carbonization-composition process with the mixture of ferrotitanium,chromium,iron powders and precursor sucrose as raw materials.In situ synthesized Fe-Cr-C and Fe-Cr-C-Ti composite coating was fabricated on substrate of Q235 steel by reactive plasma cladding process using the prepared composite powder.Microstructure of the coating was observed by scanning electron microscope(SEM),the phases in the coating were determined by X-ray diffraction(XRD).Results indicate that the Fe-Cr-C coating cracks begin from the fusion area and expand along grain boundary(Cr,Fe)₇C₃ which forms crystallization crack.The cracks expand along fiber direction of the primary carbide(Cr,Fe)₇C₃ to the coating surface,which forms the macro cracks that is vertical throughout the surface of coating.A few cracks originated in pore or edge sharp place of coating.The Fe-Cr-C coating with Ti could synthesize a lot of TiC particles and form austenite with little or without primary carbide(Cr,Fe)₇C₃ and improve the eutectic microstructure of(Cr,Fe)₇C₃.It improved the toughness and curbed the fracture of the coating effectively.