The Fractal Research Of The Interface And The Microstructure Properties Of The Vacuum Fusion Sintering Nickel-base Alloy Coating With Rare Earth Joined

The interface property of the vacuum fusion sintering Ni-base alloy coating has been researched by the fractal method.Through the fractal analysis to the alloy coating interface morphology,the relationship between the micro-hardness,diffusion coefficient,thermal fatigue property and the fractal has been constructed.The Ni-base RE alloy coating and Ni-base-WC composite coating were obtained by the technique of vacuum fusion sintering on the 45 steel.The interface morphology and the micro-structure symbol of the section were analysised with the method of SEM.Also the micro-hardness destruction values in the two sides of the vertical section were measured by the micro sclerometer. The values were analysised.Use the EDS ,the contents of the certain element in the two sides of the coating were measured, then the diffusion coefficient calculation equation was deduced,which could calculate the element diffusion coefficient value in the certain depth.To the thermal fatigue property,there were some analysis in this paper.The interface and surface of the coating are nonlinear,belong to random fractal,also the geometrical shape with the certain fractal dimension.Different coatings have different interface morphology, the fractal dimension of the certain coating vertical section with the fractal was calculated.For the fractal dimension show the "random degree" of the fractal graph ,the certain fractal dimension value corresponds the certain alloy coating.In this paper, the preparation materials were vacuum fusion sintering NiCrBSi-RE alloy coating which the different content and sort were added and the composite coating with different WC content. The relationship between the fractal dimension of the coating vertical section and the distribution of the micro-hardness,thermal fatigue property,micro-structure.Then the aim that the fractal dimension symbolize the coating macro-property was gotten which would take a new method to the material analysis.According to the research result,the fractal dimension values correspond to the different microstructure,the micro-hardness distribution value,the thermal fatigue property.Generally,the fractal dimensions of the alloy coatings with RE are larger than the ones of the alloy coating without RE addition,the micro-hardness distribution values are also higher.Comparing to the microstructure,the column-shape crystal areas were more obvious,the spherical pharse were more and the neddle phases lessened in the interface fusion areas of the alloy coating with RE.To the composite coating which the WC was added,the WC appeared with the spherical dispersion which improved the comprehensive property of the coating.Corresponding to the fractal dimension,the values became higer.The alloy coatings which their fractal dimension values were larger than 1.77 had the better thermal fatigue property,while the ones less than 1.75,their thermal fatigue property were worse.