Surface Engineering Techniques and Applications
1. XRD Techniques Used for Stress Measurements
It uses Bragg’s law = 2dsenσ, the elastic relation to obtain stress value.
Advantages:
- Non-destructive
- Fast, simple
- Can be done in situ
- High accuracy
Disadvantages:
It is much more accurate for measuring large crystalline structures rather than small ones.
Examples:
- Sampling of geological specimens
- Material characterization
2. Chemical Vapor Deposition (CVD)
Definition: A chemical process used to produce high-purity, high-performance solid materials.
Experimental Methods:
- Atmospheric Pressure Chemical Vapour Deposition (APCVD)
- Low Pressure Chemical Vapour Deposition (LPCVD)
- Metalorganic Chemical Vapor Deposition (MOCVD)
Examples of materials: Silicon, carbon fiber, carbon nanofiber, etc.
Advantages:
- High growth rates possible
- Can deposit materials which are hard to evaporate
- Good reproducibility
- Can grow epitaxial films
Disadvantages:
- High temperatures
- Complex processes
- Toxic and corrosive gases
3. Painting Coating
It is a type of coating applied as a dry powder. It involves three steps: surface preparation, application of dry powder/heating, and inspection.
Examples of applications:
- Appliances: refrigerators
- Automotive: wheels, bumpers
Advantages:
- Powder is generally less flammable than liquid coating
- No waste of coating
- Low operating cost
Disadvantages:
- Start-up costs
- Color change difficulties
4. XPS
XPS measures the elemental composition, chemical state, and electronic state of elements.
Advantages:
- Can probe down to core electrons
- Can differentiate between oxidation states
Limitations:
Spectra take a long time to be obtained, limited organic information.
Examples:
- Polymers and adhesives
- Heterogeneous catalysis
5. Electrodeposition
It is the process of producing a coating on a surface by the action of an electric current.
Experimental Methods:
- Electroplating
- Electrophoretic deposition
Advantages:
- Uniform coating thickness
- Easy control
- High speed of coating
Disadvantages:
- Costly and time-consuming
- Non-uniform plating
Examples:
- Anticorrosion
- Automobile parts
6. Physical Vapor Deposition
It is a vaporization coating technique involving the transfer of material on an atomic level.
Methods:
- Sputtering
- Evaporation
Examples: Thin film solar panels
Advantages:
- Improved properties compared to substrate material
- Environmentally friendly process
Disadvantages:
- High capital cost
- Slow coating deposition
7. Hot-Dip Galvanizing
It is the process of coating iron, steel, or aluminum with a zinc layer.
Advantages:
- Versatile process
- Long life
- Protects against corrosion
Disadvantages:
- Location limitations of galvanizing plants
- Cannot be applied to existing structures
Examples:
- Pressed steel water tanks
- Guardrails
8. SIMS
SIMS analyzes the composition of solid surfaces and thin films by sputtering the surface with a focused primary ion beam.
Advantages:
- Consumes very little sample
- No complex sample preparation
Limitations:
- Not all elements can be analyzed quantitatively
- Expensive
Examples of application:
- Semiconductors
- Superconductors
9. STM and AFM
STM: Scanning Tunneling Microscopy. AFM: Atomic Force Microscopy.
Advantages:
- High resolution
- Works in air or liquid environment
Disadvantages:
- Difficult to determine detailed shape
- Slow scanning
Examples of application:
- Roughness measurement
- Atom manipulation
10. Techniques Based on Micro-Tips for Electrochemical Behavior
Capillary-based technique and Scanning Reference Electrode Technique.
11. Tribocorrosion
An irreversible material degradation process due to the combined effect of corrosion and wear.
Main mechanisms involved:
- Wear
- Corrosion
- Friction
- Fatigue
12. Surfacing by Welding
The addition of metal to a surface for component restoration.
Methods:
- Arc Welding
- Gas Welding
- Resistance Welding
- Energy Beam Welding
- Solid-state Welding
13. Surface Engineering
Deals with altering the properties of the surface phase to reduce degradation over time.
Applications:
Used in automotive, aerospace, biomedical, textile, and more.
14. SEM and TEM
Scanning Electron Microscopy and Transmission Electron Microscopy.
Advantages:
- Direct imaging of crystalline lattice
- High-quality images
Disadvantages:
- Difficult sample preparation
- Special training needed
15. AES
Auger Electron Spectroscopy provides elemental and chemical state information from solid surfaces.
Advantages:
- High spatial resolution
- Fast analysis
Limitations:
- Insulators are difficult to study
- Destructive technique
16. Capillary Techniques for Electrochemical Behavior
Techniques using glass microcapillaries filled with electrolyte to study surfaces at the microscale.