Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Manufacturing Processes > Coating and Deposition Processes > Flashcards

Coating and Deposition Processes Flashcards

1
Q

Principal and reasons for Coating and Deposition Processes?

A

 Principal reasons for coating

 Improve resistance to wear, fatigue, erosion or indentation

 Improve resistance to corrosion and oxidation

 Reduce and control friction of surfaces

 Increase electrical conductivity or electrical resistance

 Rebuild worn or eroded surfaces during service

 Enhance product appearance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the typical classification of coating processes?

A
  • Plating processes
  • Conversion coating
  • Physical vapour deposition
  • Chemical vapour deposition
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

The principle/method behind Electroplating?

A

A cathode workpiece is plated with a different metal (anode) which is transferred through an electrolyte solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Electroplating Process Mechanism?

A

Rack Plating
Barrel Plating
Strip Plating
Brush Processing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the two electrolyte solutions?

A

Strong acids or cyanide solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Name three coating metals and their purpose?

A

Nickel Copper - Often used as intermediate layers providing bright finish and smooth surfaces, corrosion resistant and electrical conductivity

Chromium - Corrosion protection, wear resistance, decorative

Hard Chroming- corrosion protection, wear resistance

Zinc - Barrier corrosion protection for steel

Tin - barrier corrosion protection and increase of solderability

Gold- decorative, thermal and electrical conductivity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Advantages of Electroplating

A
  • No size limitation of the workpiece
  • Simple and complex shapes
  • Basic tooling requirements; some costs for jigs and fixtures
  • Medium labour costs
    Suitable for both, one-off and high volume production
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Limitations of Electroplating

A
  • Significant health and safety requirements
  • Strict environmental controls are essential
  • Complex shapes may require altered geometries
  • Significant preparation of the workpiece required (chemical cleaning and degreasing)

-Moderate cycle times
Some post-processing (fine polishing) required

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is electroless plating and how is it different form electroplating?

A

Electroless plating - Deposition of metal onto the workpiece surface in a solution containing ions of the plating metal by chemical reaction only.

Difference - Difference is electroplating uses an external power source compared to electroless plating where the material reacts to the solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is electroforming ?

A
  • Metal is electro-deposited onto a mandrel (pattern) using the principle of electroplating producing a coated shell (final workpiece)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the coating metals of electroforming?

A

Nickel, copper, silver, gold and soft materials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are some the applications of Electroforming?

A

Fine moulding tools for lenses, plates for printing

Biomedical equipment

Electro-optics and electronics equipment

Decorative applications – fittings, tableware
Jewellery, sculptures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is Hot Dipping - Galvanising?

A

Hot dip galvanizing is the process of coating iron or steel with a layer of zinc by immersing the metal in a bath of molten zinc at high temperatures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Process of Galvanising?

A

Cleaning and degreasing process – workpiece is cleaned with caustic acid, hydrochloric acid (pickling bath) and final wash

Dipped in zinc-ammonium chloride (flux) to prepare for galvanising

Galvanised by dipping in a bath of molten zinc (450°C) or centrifugal galvanising for more uniform and even coating

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Applications of Galvanising?

A

Architectural steelworks, bridges, walls

Agricultural hardware

Automotive chassis

Furniture

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is Conversion Coating or Phosphate coating?

A

Thin film of oxide, phosphate or chromate is formed on a metallic surface by chemical or electrochemical reaction

17
Q

What are the two categories within conversion coating?

A
  • Phosphate and chromate coating – by chemical reaction only

- Anodising – oxide coating by electrochemical reaction

18
Q

What are the few reasons for conversion coating?

A

Corrosion protection and wear reduction

Preparation for painting

Increased electrical
resistance of surfaces

Decorative finish

19
Q

What is method and principle of Phosphate coating?

A

Surface of the metal is chemically treated to produce non-metallic, non-conductive surfaces

Coating is formed by immersing the base metal (usually zinc, steel) in a bath where phosphate salts (zinc, magnesium, calcium) have been dissolved in solutions of phosphoric acid

20
Q

What is method and principle of Chromate coating?

A

Surface of the metal is chemically treated to produce non-metallic, non-conductive surfaces

Coating is formed by immersing the base metal (aluminium, copper, magnesium, zinc, cadmium, silver) in a bath where chromate salts have been dissolved in solutions of chromic acid

21
Q

Anodising what is the principle and method behind it?

A

Workpiece surface (aluminium, magnesium, titanium) is converted to a hard and porous oxide layer by applying a DC current while being submerged in an electrolytic solution

22
Q

What is Anodising?

A

Workpiece surface (aluminium, magnesium, titanium) is converted to a hard and porous oxide layer by applying a DC current while being submerged in an electrolytic solution

23
Q

What are the applications of anodising ?

A
  • Automotive aluminium components
  • Furniture and architectural shapes
  • Consumer electronics
24
Q

What is the principle behind Physical Vapour Deposition(PVD)?

A

Material is converted into its vapour phase in a vacuum chamber and condensed onto a substrate surface as a very thin film

25
Q

What is the process mechanism of PVD?

A

Vaporization of the material from a solid source assisted by high temperature vacuum or gaseous plasma.

Transportation of the vapor in vacuum or partial vacuum to the substrate surface.

Condensation onto the substrate to generate thin films.

26
Q

What are the two most common PVD processes?

A
  • Vacuum Evaporation

- Sputtering

27
Q

Process Mechanism of PVD (Sputtering)

A

Energising inert gas (e.g. argon) by means of an electric field to form a plasma

Bombardment of the cathodic coating material with argon ions (Ar+)

28
Q

Difference between Vacuum Evaporation and Sputtering (PVD)?

A

Sputtering causes a gaseous or cloud around the material compared to vacuum.

29
Q

Application of PVD?

A

Electronic components – electrical connections on printed circuit boards; electromagnetic interference (EMI) or radio frequency shielding

Decorative coatings on plastics and metals – trophies, automotive trim, toys, jewellery

Automotive light reflectors – heat and light deflection

Antireflection coating on optical lenses

Coating on cutting tools and injection moulding tools

30
Q

PVD Advantages?

A

Capable of coating substrate with metals, alloys, and refractories

Preserving substrate metallurgy

Applicable for coating all tooling

Fine particle deposition (PVD evaporation)

Very good adhesion properties (PVD sputtering better than evaporation processes)

Reasonable quantities per batch (PVD evaporation)

31
Q

PVD Limitations ?

A

High level of cleanliness required

Parts require fixturing and orientation in line-of-sight process (PVD evaporation)

Slower deposition rates with PVD sputtering compared to PVD evaporation

Difficult process control with PVD sputtering compared to PVD evaporation (traces of gas can be found in the coated film)

32
Q

Chemical Vapour Deposition CVD

A

Chemical decomposition of gas constituents from interacting gas mixtures form a solid film on the substrate surface

33
Q

What is the process involved in CVD?

A

Reactant gases are introduced into a heated chamber (reactor)

Heating of substrate (deposition temperature 250-2,000°C)

Chemical reaction of the gases lead to layer deposition

34
Q

Advantages of CVD?

A

Capability to deposit refractory materials at temperatures below their melting points

Excellent adhesion

Deposition does not require a vacuum

Large quantities per batch

Short reaction times reduce stresses on substrate

35
Q

CVD Limitations

A

Corrosive and toxic elements require special closed chamber pumping and disposal equipment

High temperatures can affect substrate metallurgy

Expensive deposition material

Poor material utilisation

Manufacturing Processes (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions