O’zbekistоn respublikasi оliy va o’rta maxsus ta`lim vazirligi

Hardening of surfaces with a laser beam
When exposed to a laser beam on a metal surface, it quickly heats up to a high temperature and immediately cools down when the irradiation stops. It turns out a kind of hardening of the surface. Such hardening with a laser beam can be used for processing steel and cast iron parts in order to increase their wear resistance.
Laser hardening of surfaces makes it possible to selectively change the properties of various parts of machine parts and tools, as a result of which it is possible to obtain stronger wear and corrosion-resistant surfaces. It has a number of features that compare favorably with other methods and methods of hardening: the locality of the hardening process, the possibility of processing hard-to-reach places, obtaining a given surface roughness, the possibility of obtaining a layer with desired properties on the surface of the part; the possibility of automating the process, etc. In addition, this method can not only strengthen the surface layer of the workpieces. The use of laser machines of the Kvant-16 model for hardening the cut-off edges of fuel pump plungers, running rollers and camshaft cams of internal combustion engines can significantly increase wear resistance and extend their durability.
Many parts that experience significant contact loads are subjected to laser hardening. After such hardening, the contact wear resistance and strength of the edges of the valve discs, the working surfaces of the pressure spools of the fuel equipment, the heads of the rods and seats of the exhaust valves, the working surfaces of the measuring tool, etc., significantly increase. high-pressure pipeline fittings on the SLS 10-1 laser machine made it possible to obtain hardened zones along the contact circle of the spool. The hardened zone is a set of laser beam focusing spots with a step of 0.75 and a width of 0.6 mm. Such hardening leads to an increase in the resistance of the valve joint by more than 3 times.
A great effect from the use of this method is achieved by hardening punches and die matrices, the durability of which depends on the hardness and surface condition of their working elements. Laser hardening of these elements is carried out after their final mechanical treatment, and the power density of laser radiation should not exceed the critical value when the surface layer of the material being processed is melted.
Laser hardening is used with high efficiency for processing the journals and fillets of crankshafts, the sides of the annular undercuts of pistons of internal combustion engines, the teeth and end surfaces of helical gears, etc. Laser hardening makes it possible to obtain a stably uniform hardened layer, which is practically unattainable with other processing methods. In this case, the hardening depth, depending on the material and processing modes, reaches (1 ... 2) mm. Laser hardening can be subjected to cast-iron guides of machine beds. Such hardening makes it possible to bring their hardness up to HRC 60.
In some cases, during laser hardening of parts, alloying elements are applied to their surface. In this case, it is necessary that the temperature on the surface slightly exceeds the melting point of the alloying element. In the process of melting the metal, it is intensively mixed with alloying elements placed on the surface to be treated. The doping depth is determined by the beam power, its diameter and scanning speed. When alloying, for example, carbon steel with cobalt, the layer depth reaches 1.2 mm, while the wear resistance of parts increases by (3...4) times.