A Study Of Microstructure And Interface Of WC-Ni By Flame Spraying

Because of the high hardness, strength, superior corrosion resistance and wear resistance, cemented carbiede is popular in machining cutting tools, geological mining exploration mining tools, precision mould, wear parts and so on. Using flame spraying for preparation of WC-Ni carbide coating which is hard on surface and tough in core has been paid much attention in recent years. A large number of researches which study the technology conditions influence on the properties of the coatings has been reported widely, but researches concerned about the interface and microstructure organization inside coatings is rare. However, the influence of microstructure on the coating performance is critical and is directly related to understand the essence of materials.This thesis will focus on testing the WC-Ni carbide coating internal organization and interface theory analysis. First of all, using XRD for phase analysis from WC-Ni powder to sprayed coating, SEM observation for the morphology formation of the coating surface and cross-section, finally using TEM analysis for micro zone WC-Ni organization structure and the formation of the second phase particles. Results show that there are holes between particles after spraying coating, the WC grains grow up with uniform distribution and the new phase WC1-x has been detected. Then, misfit analysis with O-lattice theory and good matching site approach can obtain the preferred orientation relationship whose mismatching is small. Based on the misfit analysis, ?g parallelism rule was used to predict the preferred interface between WC and Ni phases. From the calculation results, the preferred interface I1 and I2 which miller index is (111.24) and (111.15) can be obtained when the rotation angle is 6.64°and 21.12°. The preferred interface has a series of periodical terraces with secondary dislocations which can decrease the interfacial misfit efficiently.