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Double Glow Plasma Nitriding Of Zr46Ti44Al5V5 Alloy And Its Properties

Posted on:2017-05-09Degree:MasterType:Thesis
Country:ChinaCandidate:H L LinFull Text:PDF
GTID:2311330536454171Subject:Materials engineering
Abstract/Summary:PDF Full Text Request
Zr-Ti alloy has become the structure materials of nuclear reactor,because of its special radiation resistant,moderate mechanical properties,the small thermal neutron absorption cross section,and superior compatibility with uranium.Zr-Ti alloy has good corrosion resistance in most of the acid,alkali and some molten salt,So it also had was used in the aviation and chemical industry;But characteristics of low strength and poor wear resistance has hinder its wide range of applications.Nitriding is one of the effective methods to improve the surface wear resistance and hardness.In mechanical properties:the optimum parameters of the nitrided samples as follows:source voltage 940-970 V,cathode voltage 610-640 V,the distance of source-cathode fixed at 15 mm,temperature 850 ?,holding time 5h,working pressure 130 Pa,and the optimal thickness of the coating is 420?m,the surface hardness is 975 HV.The optimum parametershe of the corrosion resistant as follows: the source voltage is 940-970 V,the cathode voltage is 610-640 V,the source-cathode is fixed at 15 mm,and the heating temperature is 850?,the holding time is 8h,the working pressure is 130 Pa.the optimal thickness of the coating is 460?m and the hardness of the surface layer is 963 HV.After XRD and EDS analysis,the modified layer is mainly composed of Ti2N,TiN,ZrN and a small amount of ?VN.These high hardness phases are also the reason why the hardness and the corrosion resistance are remarkably improved.The friction coefficient of the nitriding layer is obviously reduced,which indicates that the nitriding has a certain anti-friction effect.The wear depth of the nitrided specimen is obviously less than that of the original sample,the surface layer is only a certain tearing,its main mechanism is fatigue wear,accompanied by abrasive wear.But the original sample evidently has the furrow phenomenon,the wear mechanism is a mixed mechanism of adhesive wear and abrasive wear;Compared with the original sample,the weight loss of the nitrided specimen is obviously reduced.Which indicates that the abrasion resistance of the modified layer is remarkably improved.In the electrochemical experiments,the corrosion resistance of the best process in each group comparison have significantly improved of 0.5mol / L H2SO4 and 3.5% NaCl solution,but the corrosion resistance was decreased in 1mol / L NaOH solution.
Keywords/Search Tags:Double glow plasma nitriding, Layer thickness, Hardness, Wear resistance, Corrosion resistance
PDF Full Text Request
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