Strength of Cylindrical Specimens Subjected to Laser Hardening along the Generator and a Spiral Path

We have shown that the path of a continuous CO₂-laser beam over the cylindrical surface of specimens in the course of their hardening substantially affects the strength of steels in cyclic axial tension and bending with torsion. Hardening on a spiral path ensures higher mechanical parameters as compared with that along the generator of the cylindrical surface.     

Crack Formation in Gas-Thermal Coatings Depending on the Conditions of Their Laser Remelting

In the course of heating of Fe–Cr–B–Al electrometallized coatings on low-alloy steel by a scanning CO₂ laser beam, cracks, oriented mainly perpendicularly to the direction of scanning, can be initiated in the paths of the remelted coating. If the depth of the coating is small, the number of cracks and their width are greater. If the depth of remelting is comparable with the initial thickness of the coating, the number of cracks after its remelting decreases sharply.     

Fracture of Laser-Hardened Cylindrical Rods Caused by Torsion and Tension

We study the influence of the direction of motion of a laser beam over the surface of a cylindrical rod in the process of hardening on its strength and character of fracture caused by torsion. The process of hardening of specimens made of 45 steel performed in the tangential direction along a spiral and in the longitudinal direction along the generatrix with different degrees of overlapping of laser tracks results in the formation of an anisotropic structure, which strongly affects the investigated characteristics. The best results are obtained in the case where the direction of deformation of the rods coincides with the direction of screwing of a nut on a right-hand screw and the material of hardened tracks works in compression. In the case of torsion in the opposite direction, the material of hardened tracks works in tension and the strength of the specimens slightly increases. At the same time, their plasticity abruptly decreases.     

Structural Changes in the Surface Layer of D16 Alloy Cladded with Aluminum in the Process of Laser Heating

We demonstrate the changes in the microstructure of the surface layers of D16 alloy cladded with aluminum in the course of laser treatment. The process of melting can start for relatively low intensities of laser beams on the interface of the alloy and clad layer with subsequent propagation of the front of melting both into the bulk of the alloy and to the surface. As the intensity of laser irradiation increases, the process of melting starts from the surface and the thickness of the remelted and recrystallized layer increases. Laser heating removes textures and decreases the microhardness of the surface layers of the alloy.     

Wear Resistance of Laser-Modified Arc-Sprayed Coatings Made of FMI-2 Powder Wires

A fine crystal nonporous structure of arc-sprayed coatings with uniformly distributed chemical elements can be obtained as a result of optimization of the parameters of laser treatment. The wear resistance of these coatings under the conditions of boundary friction and abrasive wear also significantly increases.     

Structure and Properties of Aluminum Alloys Modified with Silicon Carbide by Laser Surface Treatment

We study the structure and properties of AA6082 and AA7075 aluminum alloys modified with particles of SiC with the help of a laser. It is shown that the wear resistance of alloys laser reinforced with SiC in the case of friction against an abrasive wheel is 30–75 times higher than for nonmodified alloys. On the basis of the data of electrochemical investigations, it is shown that, for AA7075 alloy, the influence of its structural heterogeneity on the variation of corrosion potentials decreases as the corrosion activity of the medium increases. We measured the values of corrosion currents of the surfaces of alloys in various corrosive solutions. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 3, pp. 34–40, May–June, 2005.