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Research on the Preparition of Ni-based Self-fluxing Alloy Powder and the Performance of Anti-corruption of the Coating of It

Author: ZhaoLiMei
Tutor: YangRuiCheng
School: Lanzhou University of Technology
Course: Materials Science
Keywords: Nickel-based self-fluxing alloy powder Of plasma spray Oxygen - acetylene flame spray Electrochemical corrosion Anodic polarization High-temperature oxidation Oxidation Kinetics Thermal fatigue
CLC: TG174
Type: Master's thesis
Year: 2007
Downloads: 359
Quote: 1
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Abstract


As one of the three main failure mode of mechanical parts, corrosion problems directly related to the various fields of the national economy. In view of this, based on the quality of this article percentile factor (APF = 4Cr / (2Mo W)) method, with reference to advanced corrosion resistant alloy, and our group's previous work, the design of a new Ni-based self-fluxing corrosion alloy powder. With oxygen - acetylene flame spray, plasma spray powder thermal spray homemade preparation of a corrosion resistant alloy coating on low carbon steel substrate. From the quality of the coating on coating performance and its mechanism of electrochemical corrosion, high temperature oxidation and thermal fatigue. By comparing two coating morphology, composition phase, the number of defects and their distribution, the microhardness change as well as the binding region of element diffusion can be found to form a metallurgical bond between the two coating and the substrate, such as plasma spray layer The quality is higher than oxygen - acetylene welding layer. By measuring both coatings and 1Cr18Ni9Ti stainless steel in different concentration H 2 the SO 4 , 10% HCl, mixed acid (15% HCl and 15% H SO 4 10% H 3 PO 4 10% HNO 3 ) and saturated FeCl 3 solution in the anodic polarization curves obtained two coatings, stainless steel in the same electrolyte, and the coating of the same composition of the different electrolyte corrosion potential, the corrosion current, passive current and breakdown voltage, etc. . The experimental results show that both coatings first increase and then decrease as the corrosion rate of increase in the concentration of sulfuric acid, was easy to form a passive film formation from the first difficult to. In different concentrations of sulfuric acid, the two coatings form a protective passivation film. 10% HCl and FeCl 3 , the minimum rate of corrosion of stainless steel corrosion rate, plasma spray layer. In the mixed acid, when the potential reached 1.2V, the polarization curves of the two coatings is relatively flat, and there have been passivated, the late that the coating is in a stable state, the corrosion rate is small. Stainless steel anode polarization curve serrated: stainless steel surface passivation film soon dissolved, did not play a protective role. Corrosion late stainless steel polarization curve rose sharply becomes large, the corrosion rate. Weight gain two coatings 1Cr18Ni9Ti stainless steel 750 ℃ ??high temperature oxidation resistance, and the morphology of the oxidation products by SEM and XRD and phase composition of the observation and analysis, and oxidation of the coating weight gain nonlinear fitting curve. The results show that the two coating oxidation weight gain curves parabolic law, the oxidation products of the coating Cr the 2 O 3 . Stainless oxidation after 100 hours of oxidation reaction product does not exist in the CR 2 O 3 , two coatings in a high-temperature long showed a superior oxidation resistance. The different thickness of the thermal sprayed sample was put in a muffle furnace for thermal fatigue. The experimental results show that when the two spray welding layer has a thickness greater than 5mm, the thermal fatigue resistance of the coating will be greatly reduced. When the coating is less than 3mm, the two coatings are not shedding phenomenon. Earlier than plasma spray layer, oxygen - acetylene flame spray layer cracks crack more than the number of plasma spray layer, and the crack growth rate is relatively fast.

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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
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