Engineering Commons^™

Development Of Low Alloy Steel By Direct Metal Laser Sintering, Elias Jelis

Dissertations

The US Department of Defense is interested in developing, understanding, and optimizing process parameters for low alloy (4340/4140 steel) for the powder bed fusion process. Low alloy steel is used in parts where high strength and toughness are required. During parameter optimization, several aspects of the process are investigated. Powder size and morphology optimization is important for manufacturability because adequate packing is required to produce full density components. Microstructure evaluation is used in order to provide insight into parameters that lead to optimal mechanical performance and recoating performance. Influence of residual stress is evaluated with this process. Large thermal stress …

Synthesis And Characterization Of Atmospheric Pressure Chemically Vapor Deposited Aluminum, Sipeng Gu

Dissertations

This study investigates the use of atmospheric pressure chemical vapor deposition (APCVD) to produce high quality aluminum coatings for corrosion protection of steel. The coatings were produced through thermal decomposition of tri-isobutyl-aluminum (TIBAL) over the 275 to 300°C temperature range. Under optimal deposition conditions, growth rates as high as 1.2 um/min were achieved. X-ray photoelectron spectroscopy, auger electron spectroscopy, glow discharge optical emission spectroscopy and nuclear reaction analysis revealed that the coatings consisted essentially of pure aluminum (~99 at.%) with oxygen and carbon present as minor constituents. The coatings were characterized in terms of their morphological, structural, electrical, and mechanical …

Characterization Of Thermally Diffused Bordie Layers On Aisi 1018 Steel : Residual Stresses (By Synchrotron Radiation) And Microhardness, Joel A. Payne

Theses

Boronization is a thermal diffusion process in which needle like boride layers are formed at the surface of the metallic substrate. The boride coatings formed by the diffusion process have high hardness and strong ware and corrosion resistance. In order for coatings of this nature to be industrially successful, their service life should be long and characterization should be extensive. Measuring the residual stresses of the coatings caters to each of these aspects.

In this study, AISI 1018 steel samples were boronized by a powder-pack process for four hours at 850°C in an argon atmosphere. Characterization techniques included coating thickness, …

Performance-Based Seismic Engineering Of Low And Medium-Rise Steel Frames, Saeid Rashidi

Dissertations

The performance level of low and medium-rise steel frames designed according to the common force/strength approach of the UBC or NEHRP is determined. Several combinations of soil profile type, lateral-force-resisting system, and frame-member proportioning are included in the designs.

To evaluate the expected damage, nonlinear models of the designed frames are subjected to a number of actual and simulated ground motion accelerograms and appropriate structural response parameters such as, interstory drift, ductility demand, and dissipated hysteretic energy are obtained. In addition, a modified form of Park-Ang damage index is calculated for moment-resisting frames. The seismic performance of the steel frames …

Characterization Of Steel Corrosion In An Aggressive Environment, Sung Min Maeng

Theses

As part of the Sustainable Green Manufacturing Program, the corrosion resistance of sputtered tantalum is being studied in order to evaluate it as a replacement coating for electroplated chrome. To accomplish this, studies were conducted to evaluate corrosion properties of the gun barrel steel by employing corrosion rate and bulk measurements including x-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive x-ray spectroscopy (EDX), and x-ray fluorescence (XRF), as well as synchrotron-based x-ray absorption spectroscopy (XAS).

Corrosion behavior of steel immersed in an aggressive environment of 37.8 % hydrochloric acid at room temperature was investigated as a function of time from …

The Corrosion Of Zinc-Stainless Steel Couples In Flowing Sea Water, Henry Shaw

Theses

The effect of sea water flow on passivated stainless steel 304 coupled to high purity zinc was studied for more than 1000 hours at 23°C. The corrosion of both members of the couple increased over that of the metals alone. Zinc suffered severe pitting while the Stainless Steel was not visibly corroded, When the metals were exposed alone, zinc corroded uniformly while the stainless steel was not affected at all. The use of zinc coupled to Stainless Steel is not recommended in systems exposed to sea water.