عنوان

Potential risk of hydrogen embrittlement of Zn-Ni coated high strength steel

Number

TL49191

.Language of Text, Soundtrack etc

انگلیسی

Title Proper

Potential risk of hydrogen embrittlement of Zn-Ni coated high strength steel

General Material Designation

[Thesis]

First Statement of Responsibility

Md Saimon Islam

Subsequent Statement of Responsibility

Montoya, Arturo

Name of Publisher, Distributor, etc.

The University of Texas at San Antonio

Date of Publication, Distribution, etc.

2016

Specific Material Designation and Extent of Item

85

Text of Note

Committee members: Govindaraju, Madhavrao; Maldonado, Victor

Text of Note

Place of publication: United States, Ann Arbor; ISBN=978-1-369-44024-9

Dissertation or thesis details and type of degree

M.S.

Discipline of degree

Mechanical Engineering

Body granting the degree

The University of Texas at San Antonio

Text preceding or following the note

2016

Text of Note

Within the aircraft industry, high strength steels have been used for aircraft components (e.g., main landing gear, fasteners, etc). These steels have traditionally been protected using cadmium electroplating. As a result of the carcinogenic nature of cadmium, its use has been severely restricted. Electroplated ZnNi has been identified as a replacement material for the cadmium coating. Demonstration plating lines have been implemented in both Air Force and NAVAIR depots. However, the effects of hydrogen generated from differences in electrochemical potential between the ZnNi coating and exposed steel at a defect site have raised concern. The objective of this work is to determine the potential effect of hydrogen on the susceptibility of ZnNi coated 4340 steel to Hydrogen Embrittlement. In this work, susceptibility of the substrate AISI 4340 steel to HE as a function of cathodic potential will be shown. Slow strain rate tests (SSRT) of smooth bar samples made of high strength AISI 4340 are being conducted to determine susceptibility to HE. In the first set of SSR experiments, bare steel samples were exposed to a NaCl immersion environment while being held at one of five different electrochemical potentials. The effect of potential on time to failure and other properties will be explored. A second set of SSR tests were performed under atmospheric exposure conditions at 84% RH. This value of RH is above the deliquescence point of NaCl and was controlled within the enclosed SSR test cell using a saturated solution of Sodium Sulfate at the bottom of the cell. NaCl salt was deposited on the SSR sample gauge section by a salt spray technique. Filter paper soaked in saturated NaCl solution was used to act as a salt bridge for the reference and counter electrodes under atmospheric condition. The effect of electrochemical potential on the cracking behavior of the atmospherically exposed samples will also be described. SEM characterization of the fractured samples was performed to validate embrittlement. Results from this effort will be used by both the Air Force and Navy to assess the need for enhanced risk based inspection of ZnNi coated steel parts. Engineering modeling was done for different defect sizes on the sample and results were used to validate engineering modeling approaches to predict corrosion and cracking performance during system design.

Mechanical engineering; Materials science

Subject Term

Applied sciences

Alhamami, Mohamed Tariq

Montoya, Arturo

Subdivision

Mechanical Engineering

The University of Texas at San Antonio

Call Number

1865328082; 10240023

Electronic name

p

[Thesis]

276903

a

Y