烟气轮机衬环用硬质涂层的制备及其性能研究

Investigation on the Preparation and Performance of Hard Coating for Flue Gas Turbine Transition Ring

为设计和制备烟气轮机过渡衬环用硬质涂层,确保烟气轮机长周期稳定运行,采用爆炸喷涂工艺,在304L合金基体表面设计和制备了3种Cr3C2-NiCr硬质涂层,借助X射线衍射(XRD)、扫描电子显微镜(SEM)、能谱仪(EDXA)、显微硬度计、表面粗糙度仪、万能试验机和接触角测量仪等分析测试技术,对涂层的显微组织形貌进行了分析观察,并对涂层的硬度、孔隙率、结合强度、粗糙度、热震性能和表面自由能等相关性能进行了表征。结果表明:随着氧燃比的增加,涂层的硬度单调增加,涂层的孔隙率先降低后升高。当氧燃比为1.5时,制备的涂层质量最佳,涂层的显微硬度为810 HV_(3 N),孔隙率为0.58%,结合强度为72.1 MPa,表面粗糙度为4.78μm,表面自由能为25.43 mJ/m^(2)。涂层在800℃条件下保温10 min,经室温水淬,循环20次,涂层未出现翘曲、开裂和脱落。氧燃比改变了涂层表面自由能及其分量,并对涂层表面特性产生影响。

In order to design and prepare hard coating for the flue gas turbine transition ring,and to ensure the long-term stable operation of the flue gas turbine,three kinds of Cr3C2-NiCr hard coatings were designed and prepared on the surface of 304L alloy substrate by detonation gun spraying process.By means of X-ray diffraction(XRD),scanning electron microscope(SEM),energy dispersive X-ray analysis(EDXA),microhardness tester,surface roughness tester,universal testing machine and contact angle measuring instrument,the microstructure of the coatings was analyzed and observed,and the hardness,porosity,bonding strength,roughness,thermal shock performance and surface free energy of the coatings were characterized respectively.Results showed that as the oxygen-fuel ratio increased,the hardness of the coating increased monotonously,and the porosity of the coating decreased first and then increased.When the oxygen-fuel ratio was 1.5,the quality of the as-prepared coating was the best,with a micro hardness of 810 HV_(3 N),a porosity of 0.58%,a bonding strength of 72.1 MPa,a surface roughness of 4.78μm and a surface free energy of 25.43 mJ/m^(2).After being kept at 800℃for 10 minutes and quenched with water at room temperature for 20 cycles,the coating had no warping,cracking or peelin.Besides,the oxygen-fuel ratio changed the surface free energy and its component in the coating,thus had an effect on the surface characteristics of the coating.