Surface Denaturation Layer And Formation Mechanism Of Remanufacturing Blank

Remanufacture is to repair and remake the used products based onwell-developed scientific theory and advanced technology. It’s mainly focused onthe products and components which have already been damaged and ready forreplacement, and its raw materials and final products are different to traditionalmanufacturing methods. With the increasing investment in mechanic engineering,the costs for maintaining and repairing the machine have been increasingsignificantly in China, which calls for the attention on remanufacture in industry,especially in the fields where big machine is desired. Over the year, China has put alot of effort in the West-East natural gas transmission project, however, the in-linecompressor, which is an important component for the tunnel project, is facing manyproblems due to the complexity of the work. To be more specific, a denaturationlayer will form on the surface of the vane wheel and the main bearing, causing themachine to work irregularly and affecting the remanufacture process.This article is directed at analyzing the working mode and environment ofvane wheel of in-line compressor, as well as elucidating the main factors affectingthe denaturation layer including temperature, pressure and air force. In addition, wealso proposed the scheme to simulate the vane wheel denaturation layer.Incorporating the ansys model to divide the vane wheel network, we built the flowrate model, temperature field and pressure model inside vane wheel, and calculatedthe air flow rate and force condition on the vane wheel surface. We furthercorrected the experimental procedure, ensured the vane wheel simulation schemeand put it into effect.We calculated the corrected parameters（compressibility factor） that affect gas stateequation and the thermodynamic reaction equation of CH₄-H₂,CH₄-CO mixtures. Weobtained the Gibbs temperature function△G of each reaction, demonstrated thetemperature range for metal dust corrosion as well as elucidated the reaction type ofeach reaction associated with vane wheel under different air atmosphere. Moreover,we did the thermodynamic calculation on acidic gas mixtures CH₄-H₂S, CH₄-CO₂（H₂O） and we found out H₂S,CO₂（H₂O） can both react with vane body to formFeS,FeCO₃. Since the partial pressure of H₂S is smaller than that of CO₂, thecorrosion reaction equilibrium is more shifted to the right in the case of H₂S.The denaturation layer was fabricated under different conditions using two types of materials. XPS was employed to analyze the element composition ofdenaturation layer surface and the sculpture area. The formation mechanism of thedenaturation layer was studied and it was found that the mechanisms for40CrNiMo7and1Cr18Ni9Ti denaturation layer are quite different. Under lowrotation rate, the outer-sphere composition of the40CrNiMo7denaturation layer isFe₂O₃and distinct layers are formed. At high rate, the layers diffuse substantiallyinto each other, while the compositions are different leading to multi-layer filmstructure. Under low rate, the outer-sphere composition of the1Cr18Ni9Tidenaturation layer is Fe₃O₄. At high rate, the composition changes to Fe₂O₃, on theother hand, Cr₂O₃and CrO₃are observed in the denaturation layer due to thepresence of Cr in the substrate. CrO₃only forms at high rate and its denaturationlayer exhibits a multi-layer film structure.