Abstract
It has always been a tough problem to remove carbon deposition (CD). On the inner surface of a turbo-shaft, the CD is observed by Scanning Electron Microscope (SEM) to analyze its microstructure and composition, and its formation mechanism is analyzed by X-Ray Diffraction (XRD), Infrared Spectrum (IS) and Raman spectra. Considering the physical and chemical properties of the above CD, chemically assisted magnetic grinding (CAMG) is put forward with the result to be tested by a translational permanent magnet grinding device. By analyzing the removing mechanism of CAMG, response surface analysis is adopted to analyze the influence law on surface roughness by the interactions between every two of the three following parameters, rotational speed of rotating magnetic field, needle type and grinding time. The optimal process parameters can be obtained with the rotational speed of rotating magnetic field being 600 r/min, the needle type being Φ1.0 mm×5 mm, the grinding being time 60 min. The surface quality of the work piece processed by CAMG can be comprehensively appraised through observing the microstructure, calculating the CD removal ratio and testing the surface stress. Comparing to single magnetic grinding, CAMG is more environmental-friendly and has a higher removal ratio and a better surface quality with residual stress decreasing obviously. Through professional tests, the remaining CD is less than the specified value required by the technology, which meets enterprises’ requirements.
Highlights
A turbo shaft is the main driving part of an aeroengine
To investigate the optimum process parameters for magnetic grinding, based on the preceding work, response surface analysis is adopted with the speed of the magnetic field, process time, and needle type as the main influence factors
The residual stress decreases obviously to -86 MPa, which means compressive stress, as the residual stress has been released after the surface is repeatedly impacted by the magnetic needles when the carbon deposit is removed
Summary
A turbo shaft is the main driving part of an aeroengine. Since the engine often runs at a temperature greater than 500 degrees, under catalysis of metal, carbon deposition (CD) can be produced on the inner surface of a turbo shaft after a series of oxidation reactions, pyrolysis, cracking, dehydrogenation, coking, and polymerization from the fuel in the engine (Tumuluri et al, 2017). To investigate the optimum process parameters for magnetic grinding, based on the preceding work, response surface analysis is adopted with the speed of the magnetic field, process time, and needle type as the main influence factors. Analyzing the influence factors, the optimum combination of process parameters can be obtained: the rotating speed of the magnetic field is 600 r/min, the needle type is 1.0 × 5 mm, and the grinding time is 60 min. Processing temperature during preliminary processing, is tensile with a value of +49 MPa. After magnetic grinding, the residual stress decreases obviously to -86 MPa, which means compressive stress, as the residual stress has been released after the surface is repeatedly impacted by the magnetic needles when the carbon deposit is removed. On the surface processed by CAMG, the residual stress decreases significantly to −106 MPa and is compressive
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