等离子熔覆高铬铁基涂层的开裂行为与控制

以钛铁粉、铬粉、铁粉和碳的前驱体(蔗糖)等为原料通过前驱体碳化复合技术制备了复合粉末,并通过等离子熔覆技术在Q235钢表面制备了Fe-Cr-C和Fe-Cr-C-Ti涂层.采用XRD和SEM对涂层的相组成和显微组织结构进行了分析.结果表明,Fe-Cr-C涂层裂纹一般始于熔合区,沿初生碳化物(Cr,Fe)7 C3晶界扩展成结晶裂纹,沿初生碳化物(Cr,Fe)7C3纤维方向扩展到涂层表面,形成垂直于涂层表面的垂直贯穿裂纹.少量裂纹起源于气孔或涂层边缘尖锐处.Fe-Cr-C涂层中添加Ti元素,可以合成大量TiC颗粒,形成奥氏体组织,减少或消除(Cr,Fe)7 C3初生碳化物,改善(Cr,Fe)7 C3共晶组织结构,有效提高了涂层韧性,抑制了涂层裂纹的产生.

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.