Experimental Investigation of Hydrogen Embrittlement during Coating Process and Effect on Mechanical Properties of High Strength Steel used for Fasteners

Abstract

Hydrogen embrittlement is a very important phenomenon which causes the high strength steel to fail below its permissible limit. These high strength materials are used in various industries such as power, nuclear, transport, aerospace, marine, hydrogen storage tanks etc. Hydrogen may diffuse in high strength material either internally during the manufacturing stage or externally from environment during application. Due to this hydrogen diffusion the service life of many high strength components like pressure vessels, fasteners & other stressed members may be reduced and result in unexpected failure. Hydrogen embrittlement may occur by wide variety of mechanisms such as HEDE, HELP and AIDE. Sometime the combination of these mechanisms may also responsible for hydrogen embrittlement. An attempt has been made to use the conventional tensile and impact test methods to determine the effect of process behavior on the properties of high strength steel. Specimens with different mechanical properties and heat treatment conditions were made to conduct the testing. This study determines the impact of coating especially the zinc coating process on mechanical properties of the material. Further hydrogen embrittlement prevention and development of new coatings are discussed.