Laser surface treatment of steels with CrB2 and Ni2B powders

Abstract

Results of laser surface alloying (LSA) of 1045 steel with CrB2 and Ni2B powders are presented. LSA was conducted with a 2.5 kW power cw CO2 laser. Laser treated zones were studied by optical and electron microscopy, energy dispersive spectroscopy, and by x-ray diffraction. Formation of complex borides within the treated zones resulted from the dissolution of the injected materials in the melt pool. Additionally, it was established that the dissolution extent determines the hardening mechanism provided by each type of injected material. Dissolution of injected material was found to depend mainly on their melting temperature. A study of the microstructure of treated zones showed that in the case of Ni2B the hardness increase was due to the formation of Fe2B and Fe3B. When CrB2 was used for LSA, an increase in hardness resulted from the dispersion of partially undissolved CrB2 particles, as well as iron borides (Fe2B and Fe3B) formation.

Laser surface alloying of 1045 AISI steel using Ni–CrB2 powder

“…Ni 2 B dissolved almost completely giving a combination of relatively deformed matrix (Fe phase) and hard iron borides (Fe borides which contain Ni). 13 This structure results in a hardness value of 650-800 HV while the hardness achieved when alloying with CrB or CrB 2 can reach 1000 and 1200 HV respectively.…”

“…Detailed studies of the microstructure of steel surfaces, which were created by laser induced surface alloying with CrB 2 , 9,10 CrB 11,12 and Ni 2 B 13,14 particles, revealed a partial dissolution of the added particles (CrB and CrB 2 , Ni 2 B) and the formation of iron borides, iron chromium boride and other intermetallics.…”