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Study On The HG-AFS Determination Of Trace Amount Of Arsenic, Selenium, Bismuth And Tellurium In Nickel-base Superalloy Used In Civil Aviation

Posted on:2016-05-28Degree:MasterType:Thesis
Country:ChinaCandidate:X H ZhangFull Text:PDF
GTID:2271330464454419Subject:Materials science
Abstract/Summary:PDF Full Text Request
Nickel-base superalloy has played a special and significant role in the field of high temperature alloy due to its performance and wide application in petroleum industry, nuclear industry and chemical industry, etc. In 650-1000℃, nickel-base superalloy has excellent performance,such as high strength, good fatigue resistance, radiation resistance, oxidation resistance, good processing properties and welding performance.Inconel718(GH4169,K4169 in China) is one of the most widely used nickel base superalloy, also belongs to the typical difficult-to-machine materials. Because of its very complex constitute, Elements content have crucial influence on its physical strength, chemical stability, corrosion resistance, etc. So, the control of trace impurity content is stricter than general alloy.In this thesis, arsenic, bismuth, tellurium and selenium in Inconel718 are analyzed mainly by hydride generation-atomic fluorescence spectrometry. Firstly, the hydride generation-atomic fluorescence spectrometry is introduced. Then, the related references overseas and domestic in recent years are summarized, especially for the interference elimination for multi-element determination (according to different samples). Secondly, the principle diagram of dual channel instrument (AFS-820) is introduced, and the preparation of standard solution and the reagents are listed.Thirdly, determination method of arsenic in Inconel718 by HG-AFS is established. Instrument working parameters are optimized in detail, such as lamp current, negative voltage, carrier gas flow rate, the shielding gas flow rate, the reading time and delay time, etc. Also the different optimum working conditions of the reducing agent and the interference are studied. With hydrochloric acid, nitric acid mixed dissolving the samples, thiourea-vitamin C mixture as reducer and masking agent after the reduction effect and stability of pre-reduction being considered, concentration of arsenic had a linear relation with the fluorescence intensity within 50μg/L under the conditions of hydrochloric acid (1+9) as current carrying solution, concentration of 20 g/L potassium borohydride as reductant. The detection limits (3s/k) were 0.003μg/L, The standard addition recovery was 96.8%~106%;The analysis results of nickel base superalloy standard samples were consistent with certified values by using this method, and the relative standard deviation (n=6) was less than 2%.Study on the determination of selenium in nickel base superalloy by HG-AFS shows, hydrochloric acid(5-7 mol/L)is better than other reductants. And considering matrix solutions contain selenium, So standard addition method is choosen for the determination of trace selenium in Inconel718.Then, the simultaneous determination of bismuth and tellurium in nickel base superalloy by HG-AFS has been proposed. This thesis describes the interaction between bismuth and tellurium, pre-reduction system, interference of nickel, iron, chromium, niobium and other elements and its elimination methods.With hydrochloric acid, nitric acid mixed dissolving the samples, hydrochloric acid as reducer in advance, citric acid and ammonium fluoride as masking agent, concentration of bismuth and tellurium had a linear relation with the fluorescence intensity within 10 μg/L under the conditions of hydrochloric acid (1+9) as current carrying solution, concentration of 20 g/L potassium borohydride as reductant. The detection limits (3s/k) were 0.0009 ng/L (Bi) and 0.002μg/L (Te). The standard addition recovery was 96.8%~115%;The analysis results of nickel base superalloy standard samples were consistent with certified values by using this method, and the relative standard deviation (n=6) was less than 5%.In the end, the uncertainty of determination tellurium of nickel base superalloy by HG-AFS is evaluated. The main source of uncertainty and improvement measures are summarized.
Keywords/Search Tags:HG-AFS, nickel base superalloy, As, Bi, Te, Se
PDF Full Text Request
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