(i) Welding

• Thermal Effect is the basic principle used in laser welding.
• The two ends (A & B) of the specimens are brought together.
• Now, the laser beam is focused for a long time on the ends, that are to be joined.
• Due to thermal effect, portions that are to be welded goes to the molten liquid state.
• At this particular state, atoms in the one end diffuses to the atoms in the other end.
• After that the specimen is allowed to cool slowly.
• Hence, a perfect welding can be obtained.
• Laser welds can easily be performed between two dissimilar metals.
• The Neodymium – YAG laser and Carbon dioxide laser are two important kinds of lasers that find wide ranging applications in welding.
  

(ii) Cutting

• Thermal effect is the basic principle used in laser cutting.
• The high intensity laser beam is made to fall on the material as shown in figure.
• Due to the application of laser for long time, the temperature of the material is extremely increased. It can hence be used in cutting materials.
• The most common laser that is used in cutting process is the carbon dioxide laser due to its high output power.

(iii) Heat treatment

• A powerful laser beam is allowed to hit a metal surface. That portion gets heated.
• As the beam is moved away to other areas, the heated spot cools down rapidly.
• This procedure is used for heat treatment of metal surfaces which enhances the strength of the metal.
• Laser heat treatment provides selective treatment of the desirable areas which are subjected to more intense use.
• For example laser heat treatment is used in automobile industry to strengthen cylinder blocks, valve guides, and gears camshafts etc.
• One kilowatt CO₂ laser operating in the continuous wave mode is often used for laser heat treatment.

Fig. 1.3 Laser heat treatment