Influence of laser beam treatment modes on the parameters of thermal impact zones and tribotechnical characteristics of steels

The paper presents the results of laser hardening of steels with a defocused and oscillating beam. The influence of changes in the scanning frequency, amplitude and defocusing of the laser beam on the parameters of laser quenching zones is considered. The objectives of this work were to determine the influence of the frequency of transverse vibrations, amplitude, defocusing, and the speed of movement of the laser beam for possible use in laser hardening and alloying of steels. At the first stage, single tracks with transverse fluctuations relative to the processing speed and with the scanning device turned off were applied to the surface of the samples in the center for half the length of the sample. To make the cuts, 10 mm were cut from both ends of the samples and polishing was performed according to the standard procedure. The determination of the geometric dimensions of the laser beam exposure zones was determined using a digital microscope. It is shown that the cross-sectional area of the hardened zones when using transverse beam vibrations is higher than when processing with a defocused beam, which leads to an increase in productivity during laser processing. Increasing the frequency of transverse vibrations of the beam makes it possible to obtain large volumes of molten bath on the surface, which can be used for alloying the friction surfaces of parts operating in severe operating conditions. The results obtained on laser hardening of steel with a zone width of up to 10 mm at a radiation power of 1000 W allow us to expand the technological possibilities of using laser processing. The microhardness of laser-hardened zones is 3 times higher than improved steel. The results of tribotechnical tests are presented showing an increase in the wear resistance and tear resistance of laser-hardened samples compared to steel.