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A study of surface porosity formation in deposits sprayed onto flat substrates by the Uniform Droplet Spray process

IP.com Disclosure Number: IPCOM000128083D
Original Publication Date: 1998-Dec-31
Included in the Prior Art Database: 2005-Sep-14
Document File: 7 page(s) / 23K

Publishing Venue

Software Patent Institute

Related People

Chey, Sukyoung: AUTHOR [+3]

Related Documents

http://theses.mit.edu:80/Dienst/UI/2.0/Describe/0018.mit.theses/1998-222: URL

Abstract

In the current state of spray forming processes, deposit surfaces formed on a substrate contain porosity. This surface porosity requires secondary operations to be removed. The added expense of these operations prevents the full industrialization of the spray forming process. Thus, a basic understanding of the surface porosity formation is desired. This thesis presents a fundamental analysis of surface porosity formation through modeling and experimentation. Individual splat formation and multiple splat interactions determine surface porosity in uniform droplet spray deposits. A strategy is proposed to minimize surface porosity, first, through control of individual splat formation for a suitable splat geometry, and second, through control of multiple splat interactions. Conditions for a suitable splat geometry are determined by experimentation on the effect of the droplet liquid fraction and the substrate thermal state on the final splat geometry. Pure tin droplets (416 gm) are deposited on stainless steel substrates. A droplet liquid fraction of 83% and stainless steel substrate temperature between 150 C and 190 C results in suitable splat geometry. The effect of multiple splat interactions on surface porosity is studied through modeling and experimentation. The model explains the effect of droplet flux and splat solidification on surface porosity. One dimensional heat transfer between splat and substrate is assumed. Experiments are performed with pure tin droplets (416 Rm. and 271 gm) on stainless steel and glass substrates. Results show that slower splat solidification and higher droplet flux reduce surface porosity. A minimum surface porosity of 2.2% is achieved in the uniform droplet spray deposits with tin droplets (416 gm) on a glass substrate.

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 This record is the front matter from a document that appears on a server at MIT and is used through permission from MIT. See http://theses.mit.edu:80/Dienst/UI/2.0/Describe/0018.mit.theses/1998-222 for copyright details and for the full document in image form.

A Study of Surface Porosity Formation in Deposits Sprayed onto Flat Substrates by the Uniform Droplet Spray Process

by

Sukyoung Chey
S.B., Mechanical Engineering, Seoul National University (1991) S.M., Mechanical Engineering, Massachusetts Institute of Technology (1993)

Submitted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in MECHANICAL ENGINEERING

at the Massachusetts Institute of Technology

June 1998
SIGNATURE OF author: [[signature omitted]]

Department of Mechanical Engineering

May 8, 1998
CERTIFIED BY: [[SIGNATURE OMITTED]]

Jung-Hoop Chun Associate Professor of Mechanical Engineering Chairman, Doctoral Thesis Committee ACCEPTED BY: [[SIGNATURE OMITTED]]

Ain A. Sonin

Professor of Mechanical Engineering Chairman, Department Graduate Committee ARCHIVES MASSACHUSETTS INSTITUTE OF TECHNOLOGY LIBRARIES JUL 12 1999

Massachusetts Institute of Technology Page 1 Dec 31, 1998

Page 2 of 7

A study of surface porosity formation in deposits sprayed onto flat substrates by the Uniform Droplet Spray process

A Study of Surface Porosity Formation in Deposits Sprayed onto Flat Substrates by the Uniform Droplet Spray Process

By Sukyoung Chey

Submitted to the Department of Mechanical Engineering on May 8, 1998 in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Mechanical Engineering

ABSTRACT

In the current state of spray forming processes, deposit surfaces formed on a substrate contain porosity. This surface porosity requires secondary operations to be removed. The added expense of these operations prevents the full industrialization of the spray forming process. Thus, a basic understanding of the surface porosity formation is desired. This thesis presents a fundamental analysis of surface porosity formation through modeling and experimentation.

Individual splat formation and multiple splat interactions determine surface porosity in uniform droplet spray deposits. A strategy is proposed to minimize surface porosity, first, through control of individual splat formation for a suitable splat geometry, and

second, through control of multiple splat interactions. Conditions for a suitable splat geometry are determined by experimentation on the effect of the droplet liquid fraction and the substrate thermal state on the final splat geometry. Pure tin droplets (416 gm) are deposited on stainless steel substrates. A droplet liquid fraction of 83% and stainless steel substrate temperature between 150 C and 190 C results in suitable splat geometry.

The effect of multiple splat interactions on surface porosity is studied through modeling and experimentation. The model explains the effect of droplet flux and splat solidification on su...