Doctoral Dissertations

Keywords and Phrases

Al-Si Coating Weights; Automotive Structure; Corrosion Resistance; Hot Stamping; Spot Welding; Ultra-High-Strength Steel

Abstract

"There has been increased demand for hot-stamped pre-coated Usibor 1500R in automotive industries due to its excellent properties (ultra-high strength, weight reduction, low spring back and excellent corrosion protection). In this research work, investigation was conducted to better understand the effect of Ai-Si Coating Weights on weldability and corrosion of Ultra-High-Strength Steel Usibor 1500R used in Automotive Structures”. The results show that weld nugget diameter increases with increasing weld current, better spot-weld nugget diameter is recorded at weld currents above 7.5 kA for both AS80 and AS150 and the weld current range decreases as the interdiffusion layer (IDL) thickness increases. With regards to the heat treatment, AS80 slightly shows a better weld range but heat treatment has no significant effect on welding of both AS80 and AS150, the weld diameter remained constant under the specified experimental conditions.

Both coating weights AS150 and AS80 exhibited similar excellent perforation corrosion resistance compared to 22MnB5 (Bare Usibor) due to highly protective corrosion products; AS80 and AS150 show maximum depth of corrosion attack less than 200 μm compared to 22MnB5 that has maximum depth of corrosion attack of 900 μm. AS150 displayed better resistance to cosmetic corrosion than AS80 due to thicker coating layer; AS80 coating shows higher resistance to red rust pitting corrosion than AS150 due to finer surface-morphology of AS80 as observed with SEM leading to a more homogeneous paint distribution, and E-coat thickness of 15 μm results in higher resistance to red-pitting corrosion than lower e-coat of 8 μm" -- Abstract, p. iv

Advisor(s)

Okafor, A. Chukwujekwu (Anthony Chukwujekwu)

Committee Member(s)

Dharani, Lokeswarappa R.
Chandrashekhara, K.
Park, Jonghyun
Samaranayake, V. A.

Department(s)

Mechanical and Aerospace Engineering

Degree Name

Ph. D. in Mechanical Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Summer 2024

Pagination

xi, 90 pages

Note about bibliography

Includes_bibliographical_references_(pages 28, 54 & 83-85)

Rights

©2024 Hilary Anayochukwu Onyishi , All Rights Reserved

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 12403

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