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

Abstract

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 HV3N，a porosity of 0.58%，a bonding strength of 72.1 MPa，a surface roughness of 4.78 μm and a surface free energy of 25.43 mJ/m2.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.

Keywords

• flue gas turbine|transition ring|hard coating|detonation gun spraying|oxygen-fuel ratio|performance