Tribochemical polishing is a technique that utilizes corrosive wear to polish surfaces. It involves chemically reacting the surface material with a corrosive medium like water or chemical reagent under sliding contact. The friction stimulates preferential dissolution of material at asperity peaks, making the surface very smooth after initial wear. It is effective when friction generates tribocorrosion products, mechanical stresses are low to avoid damage, and the corrosive medium is not too aggressive. Tribochemical polishing has been used to create smooth surfaces on materials like silicon nitride, silicon, and silicon carbide.

1. NATIONAL INSTITUTE OF TECHNOLOGY, HAMIRPUR
TRIBOCHEMICAL POLISHING

2. CONTENTS
1. Corrosive wear and oxidation wear
2. Tribochemistry
3. Tribochemical polishing
4. Conditions

3. CORROSIVE WEAR AND OXIDATION WEAR
 Corrosive and oxidative wear occur in a wide variety of situations both
lubricated and unlubricated.
The fundamental cause of these forms of wear is a chemical reaction between
the worn material and a corroding medium which can be either a chemical
reagent, reactive lubricant or even air.
Corrosive wear is also known as chemical wear.

4. These wear occurs when sliding takes place in the corrosive environment,
air is the most dominant corrosive medium is oxygen.
 These wear requires both chemical reaction (corrosion) and rubbing , so in
the absence of sliding there will be no corrosive wear.
 These wear are important in number of industries such as mining ,
mineral processing , chemical processing and handling.

5.  Chemical corrosive occurs because of chemical and electrochemical
intersection of interface with the environment.
Chemical corrosion occurs in a highly corrosive environment and in high
temperature and high humidity environment.
 Electrochemical corrosion is a chemical reaction accompanied by the passage
of an electric current for the occurrence of potential difference between two
regions.

6. Fig no.1 Models of interaction between a corrosive agent and a worn surface

7. The first process is dominated by the formation of durable lubricating films. If
such films are prevail then worn contacts are well lubricated and corrosive wear
does not occur.
 The second process is related to the formation of a sacrificial or short lifetime
corrosion product film under sliding contacts.
 The third process relates to wear in highly corrosive media.
 In the forth step rapid corrosion occurs on the exposed surface.

8. Fig no.2

9. TRIBOCHEMISTRY
 Chemistry dealing with the modification of chemical reaction by friction or
mechanical energy is called turbo chemistry.
 It is also defined as the chemical reactions between the surface and the
lubricant molecules inside a sliding contact under boundary lubrication
conditions.
These reactions controls the lubrication processes.
They determine the reliability and durability of moving parts in machines.

10.  The wear controlled by this reaction as called as Tribochemical wear.
 The mechanism by which friction increases the rate of chemical reaction are:-
 Heat produced at contacting asperities.
 Removal of product scale resulting in fresh surfaces.
 Accelerated diffusion.
 Mechanochemical excitation of surface bonds.

11. TRIBOCHEMICAL POLISHING
 The corrosive wear is not always an entirely destructive process.
 Corrosive wear can be utilized to produce very smooth surfaces where the
component is polished in a moderately active chemical reagent or water. This
technique is known as tribochemical or chemo-mechanical polishing.
 Tribochemical polishing has been used to generate very smooth surfaces on
silicon nitride, silicon and silicon carbide.

12. Tribochemical polishing (TCP) is a new technique for polishing
materials that is based on the friction‐stimulated dissolution of material in a
liquid.

13. Fig no. 3 Mechanism of tribochemical polishing

14. STEPS OF MECHANISM
 Chemical reaction between worn surface and corroding medium.
 Preferential removal of successive layers of oxide at asperity peaks.
 Worn surface becomes very smooth after initial wear.

15. Tribochemical polishing is effective only when the following
conditions are satisfied:
 Friction at the asperities is sufficient to generate tribocorrosion
products.
 Mechanical stresses are low to avoid any surface deformation or
fracture.
Corrosive medium is not too aggressive to cause corrosion outside the
frictional contact.

16. ADVANTAGES
High hardness.
High thermal conductivity.
Service life increases.
 Reliability increases.

17. Fig. 4 Tribochemical polishing of sic

18. THANK YOU