The influence of the cooling rate on structure of laser boronizing layer on nodular iron Available to Purchase

This article refers to laser alloying surface modifications. In presented research nodular iron laser boronizing effects were studied. The cooling rate effect on melted zone was particularly investigated. Different cooling rates were achieved by using appropriate combination of laser treatment parameters: laser beam interaction time and laser beam power. There were applied 5 laser beam velocities with constant laser beam radius r = 2 [mm]. As a result, particular samples area was heated with different interaction times from 0.25 [s] to 1.25 [s]. In order to obtain three different amounts of energy delivered to surface unit (20, 30, 40 J/mm²), different laser beam power was used. Laser treatment was performed with molecular CO₂ continuous Triumph TLF 2600t laser with 2.6-kW output power and TEM_0,1 mode. The results of the laser treatment were analyzed by means of: optical microscope, Vickers microhardness tester, Auger Electron Spectroscope, and X-ray diffraction. It was found that melted zones were almost utterly homogenous. It was stated it was possible to achieve high microhardness of those zones (even 5 times higher than core microhardness). It was showed that microhardness of melted zone created after laser boronizing increases with increasing cooling rate to critical value about 3x10³ °C/s.