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Steel surface prepared by mechanical alloying of high-Cr alloy layer

Author: HuangZhen
Tutor: ShenYiFu
School: Nanjing University of Aeronautics and Astronautics
Course: Materials Processing Engineering
Keywords: Mechanical alloying Cr alloy layer Milling speed Rare earths Cr-Al alloy layer
CLC: TG174.44
Type: Master's thesis
Year: 2008
Downloads: 62
Quote: 1
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Abstract


Mechanical alloying process, the powder cold welding and refined through the same time, part of the powder adsorbed on the ball surface and the tank wall , after repeated extrusion and cold welding , a certain thickness of the coating. According to this principle article from three different starting powder system , together with a certain degree of milling process parameters, for the first time in the inner wall of the tubular carbon materials were successfully prepared high-Cr alloy layer . X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM) and other layers of the alloy microstructure, chemical composition and phase structure analyzed and micro-hardness testing, heat shock experiments , the cyclic oxidation test , anodized related experiments to test the performance of the alloy layer . First experiments with pure Cr alloy layer powder as raw powders were set 300r/min, 400r/min, 500r/min three kinds of ball speed . Found that high-Cr alloy layer thickness by mechanical milling process parameters , and in the alloy layer and the substrate binding sites exist diffusion . Containing 10wt% RE-Si-Fe powder and 20wt% Al alloy layer prepared microstructure analysis , rare earth elements and Al, Cr is effective to increase the deposition rate and improve the thickness of the alloy layer and the diffusion layer thickness. Alloy layer performance tests show that high-Cr alloy layer hardness relative to the original matrix were greatly improved, and the hardness of the junction interface presents gradient , high temperature oxidation resistance and corrosion resistance for the phase- matrix also has a larger improved. In the milling speed is 500r/min conditions, oxidation resistance and corrosion resistance is most excellent . After adding rare earth alloy layer anti-stripping capabilities have been greatly improved, the sample in 3.5wt% NaCl solution corrosion is greatly improved. Makes the addition of Al alloy layer anti-stripping capacity improved to some extent , the alloy layer surface oxidation resistance is stronger than pure Cr alloy layer of powder samples . Preparation of the study MA mechanism of high-Cr alloy layer is that the milling process , the ball of the friction and shearing the sample surface , leading to the sample surface in a highly active state , to promote the Cr powder and the sample surface combined . Fe, Cr atomic diffusion of each other , forming a metallurgical bond of the alloy layer , while Cr cold welding made ??of composite particles continue to effect cold welding surface of the specimen , out of the alloy layer is grown .

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > Corrosion control and protection > Metal surface protection technology > Metal complex layer of protection
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