Silicide Coating for Aerospace Parts

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Our goal was to design, fabricate and test an apparatus that applies a uniform silicide coating (R512E) to the inside surface of a niobium based alloy (C-103) thrust chamber and rocket nozzle.

Silicide (R512E) Coating Apparatus for Niobium (C-103) Rocket Nozzles
Team Name Team Sprayers
Sponsors ATI Specialty Alloys and Components
Dr. Nicholas Cunningham
Mentor Dr. Steve Beyerlein
Duration Fall 2016 - Spring 2017

Project Definition


Our first specification involves achieving the desired thickness of 120 microns. Our method for ensuring a consistent coating thickness concerns the final mass of the piece. If the our procedure can produce coated nozzles with the same final mass within a certain tolerance, it follows that these nozzles with have coatings of the same thickness, assuming the coating is even across the piece.

Our second specification involves the visual quality of the coating. In order to assess how even the coating is, the nozzles will be visually observed and compared with the desired visual qualities supplied by our sponsors. These qualities are no running, no bare spots, and no clumps; basically a visually even and smooth coating on the nozzle.

Our final specification is being able to replicate the above qualities on nozzles of various sizes, from 10-28 cm. In order to achieve this, our apparatus will be adjustable in order to accommodate nozzles of various size and geometry.


The following is our Project Objective, as given by our sponsor:

"It is desirable to have a coating system that can accommodate a range of rocket nozzle sizes and produce a uniform coating thickness on the inside nozzle surface. Potential design direction include a fill and drain method where a fixture holds and seals a nozzle partly filled with glaze, while a computer controlled stage rotates and tilts the fixture in prescribed motion before draining. Glaze thickness can be estimated from weight addition and uniformity will be assessed by visual inspection."

Manipulate nozzles from 10 to 28 cm in length
Uniform inside surface coatings free of drips and runs
Simple, automated operation

Project Learning

Electrocoating Research

Electrocoating is the process of using electrical forces to attract a coating to a surface, creating a uniform and controlled coating. Electrically charged particles are deposited out of a water suspension to coat an oppositely charged part. This process is self limiting so it will not build up layers of coating on already covered areas. This results in an even coating on all surfaces and geometries.

There are four steps to this process. Pre-treatment: clean part of all foreign material and rinse thoroughly with deionized water. E-coat Bath: 80% deionized water 20% slurry. Deionized water acts as a carrier for the slurry to be deposited on part. Rinse: remove part from bath and rinse with deionized water.

Typical voltage ranges from 25-400 volts DC for this process.

Nozzle Machining

Medium Nozzle Progress
Nozzle Machining 4.jpg Finished Med Nozzle.jpg
Small Nozzle Progress
Small nozzle machining.jpg Small Nozzle.jpg

Senior Lab Sub-Projects

Mass Analysis

For this Mass Analysis Sub-Project we used the Electrocoating Method we researched to coat several aluminum samples and then compare their percent mass increases.

We used the following process:
Cathodic Deposition Process: Make bath consisting of 80% deionized water 20% paint Pre-treat part with deionized rinse Apply negative node to part and positive node to bath Dip the part in the bath for given period of time at given voltage Remove part from bath and rinse excess coating off with deionized water Bake part Factors that control thickness of deposited coating: Voltage (ranging from 20 to 400 volts DC) Temperature of bath

Power supply: Fluke DC high voltage power supply Voltage range 1V-3.5 kV Current: 1amp

Electrocoating Setup.jpg
Electrocoating Setup

Viscosity Analysis

For the Viscosity Analysis Sub-Project we used a Ford #4 Viscosity Cup to determine the viscosity of the slurry and several other paints.

To perform this test, we simply filled the Ford #4 Viscosity Cup and timed the drain of the fluid.

Viscosity Test.jpg
Viscosity Test Setup

The following are the results from this test:

Viscosity Testing.png
Viscosity Time Results

We also performed this test to try and find a surrogate coating with a viscosity similar to the slurry. To achieve this we mixed 150mL of Semi-Gloss Enamel with 100mL of water as a proof of concept for the ability to reduce the drain time. The result of this test is below:

Surrogate Testing.png
Surrogate and Slurry Comparison

Project Results

SolidWorks Nozzle Models

Nozzle Models
Small nozzle drawing for wiki.JPG
Small Nozzle
Medium nozzle drawing for wiki.JPG
Medium Nozzle
Large nozzle snapshot drawing.JPG
Large Nozzle
Sectioned Small Nozzle.jpg
Sectioned Small Nozzle
Sectioned Large Nozzle.jpg
Sectioned Large Nozzle

Completed Apparatus

Completed Apparatus.jpg
Completed Assembly

This assembly is capable of constant on-axis nozzle rotation as well as 180 degree rotation. These motions will create the conditions needed to accurately coat the inside of the nozzles.

Stepper Motor Integration

ATI Wiring.jpg
Stepper Motor Wiring

This is the circuit used for both the Nema-32 and Nema-34 Stepper Motors and their drivers.

The Nema-32 Stepper Motor was used for continuous rotation about the nozzle centerline. The Nema-34 Stepper Motor was used for 180 degree rotation about the nozzle horizontal axis.

Coated Nozzles

Nozzle Models
Coated Small Nozzle.jpg
Small Nozzle
Coated Medium Nozzle.jpg
Medium Nozzle

Team Information

Team Sprayers
Picture Biography Discipline
Tygh Picture.jpgTygh Weyand I am from central Oregon and graduated from a very small town. I chose the University of Idaho for the small class size and the town of Moscow. I enjoy anything outdoors and especially like to hunt, fish, and ride dirt bikes. Mechanical Engineering
Nick Picture.jpgNick Ferguson My home town is Chehalis, Washington. My favorite subject areas in Engineering include Robotics and SolidWorks. Some of my hobbies are writing and playing video games. Other projects I have worked on include the MeArm Robot and the Studley Tool Chest Modelling Project. Mechanical Engineering
Joe Picture 2.jpgJoe Morris I am from Spokane Washington. I work up in Alaska on a commercial fishing vessel during the summers and the rest of the year when not doing school I enjoy hunting,fishing, and mountain biking. Mechanical Engineering
Trevor Picture.jpgTrevor Livingston In addition to Mechanical Engineering I am minoring in Physics. I fight wildfires for the Idaho Department of Lands in the summer. Current and past projects include designing a method to evenly coat the interior of rocket nozzles for ATI, solar powered pool heating and filtration system, turbo-machinery analysis on a centrifugal pump, FEA analysis on a rehabilitation exoskeleton. Mechanical Engineering

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