双终点-自动电位滴定法测定镍基高温合金中铁

Determination of Iron in Nickel Base Superalloys by Double Endpoints Potentiometric Titration

建立双终点-自动电位滴定法测定镍基高温合金中铁含量的测定方法。以铂电极为指示电极,重铬酸钾标准滴定溶液为滴定剂。试料采用盐酸、硝酸和高氯酸进行溶解,用氨水将铁和共存干扰元素分离。在约10%盐酸酸度下,以钨酸钠为指示剂,用三氯化钛调至溶液变蓝,在设定的滴定程序和参数下,用重铬酸钾标准滴定溶液滴定至出现两个等当点,两个等当点的体积差为铁消耗的滴定体积,计算铁含量。考察了仪器参数、滴定介质酸度、共存元素干扰情况和干扰元素分离条件。在最优的实验条件下,对有证标准物质进行测试,并进行方法比对,允许差满足HB 5220.29—2008的要求。方法的相对标准偏差为0.16%~0.44%。方法避免了人为判断终点带来的误差,减少了目视滴定中滴定过量三氯化钛的步骤,试验操作简单,准确度高,精密度好,能够满足镍基高温合金中铁元素的测定。

A double endpoints automatic potentiometric titration method for determination of iron content in nickel base superalloys was established.The platinum electrode is used as the indicator electrode and the potassium dichromate standard titration solution is used as the titrant.The sample is dissolved by hydrochloric acid,nitric acid and perchloric acid.Iron and coexisting interfering elements are separated by ammonia.In the environment with acidity of 10%hydrochloric acid,take sodium tungstate as the indicator,titanium trichloride is used to adjust the solution to blue.Under the set titration procedure and parameters,potassium dichromate standard titration solution is used to titrate to two equivalent points.The volume difference between the two equivalent points is the titration volume of iron consumption,and calculate the iron content.Becides,the instrument parameters,acidity of the titration medium,interference of coexisting elements,and separation conditions of interfering elements were investigated.Under the optimal experimental conditions,test certified reference materials and the method comparision were conducted,and the admissible error complied with rules in HB 5220.29—2008.The relative standard deviations were 0.16%~0.44%.The method avoids the error caused by artificial endpoint determination,and reduces the steps of titrating excessive titanium trichloride in the visual titration.The test operation is simple,the accuracy is high,and the precision is good,which can meet the determination of iron in nickel base superalloys.