Laser surface treatment of steels with CrB2 and Ni2B powders

Results of laser surface alloying (LSA) of 1045 steel with CrB2 and Ni2B po wders are presented. LSA was conducted with a 2.5 kW power cw CO2 laser. La ser treated zones were studied by optical and electron microscopy, energy d ispersive spectroscopy, and by x-ray diffraction. Formation of complex bori des within the treated zones resulted from the dissolution of the injected materials in the melt pool. Additionally, it was established that the disso lution extent determines the hardening mechanism provided by each type of i njected material. Dissolution of injected material was found to depend main ly on their melting temperature. A study of the microstructure of treated z ones showed that in the case of Ni2B the hardness increase was due to the f ormation of Fe2B and Fe3B. When CrB2 was used for LSA, an increase in hardn ess resulted from the dispersion of partially undissolved CrB2 particles, a s well as iron borides (Fe2B and Fe3B) formation. (C) 1999 Laser Institute of America. [S1042-346X(99)00205-3].