There are different machining methods that causes different tensile stress in the first few layers (surface) of the metal. Some examples of these methods can be chemical etching, milling, turning and laser cutting. The tensile stress caused by these methods can reduce the fatigue resistance of the metal. This stress can be neutralized by a process which is called the straining hardening (or cold working). Cold hardening involves plastic deformation that forms a residual compressive stress in the surface layer. This can be done by several methods such as bombarding the metal surface by a metal shot.
Another promising method that can be used to reduce the tensile stress is the laser hardening. Laser hardening works by treating the surface of the metal with a powerful radiation laser pulse. This can produce a compressive stress in the metal surface which exceeds the one produced by the normal strain hardening .
This paper will look at the laser hardening technique, how it works and some of its applications. It will also show a comparison between the traditional cold working and the laser hardening from different perspectives.
Laser Hardening Technology
Laser hardening (or laser shot peening LSP), is a process that is used for hardening or peening metals using a very powerful laser. Laser peening forms a layer of residual compressive stress on the metal surface which is four times deeper than the one formed by the regular shot peening or cold working. It has been used to improve the fatigue resistance of the stressed components for more than 4 years in the aviation industry. It is also used in other industries such as the medicine industry for hardening the implants. In auto industry, laser hardening is applied for gea...
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...egions such as the inner surfaces of holes and slots of metal alloys .
Laser hardening is a promising method of increasing the fatigue resistance and strength of materials and components but it can’t replace the use of the traditional cold hardening. The high cost of the laser hardening considered to be one limitation of the technique along with the low productivity of its equipment. However these limitations can be overcome with the development of the automation and the use of robots in the industry. There are a lot of applications of this technique. The method showed a wide applications in different industries such as the aviation industry where laser hardening can be used to increase the fatigue strength, wing bolts, flight control mechanisms and structural components. Greater applicability is expected with the development of the method’s software.