Microstructure and selected properties of Fe-B coatings reinforced with B4C and Si particles produced by laser cladding using Yb:YAG disk laser

Abstract

The paper presents the study results of Fe-B coatings produced on C45 steel using laser cladding with powder technology. For this purpose, 5-axis CNC laser machining center equipped with Yb:YAG disk laser with a power rating of 1 kW and three streams powder feeding system. The powder that was used to produce Fe-B coatings was subsequently modified by the particles of boron carbide B 4 C and Si particles. The resulting powder mixture to the particles included 25 wt % respectively 20% B 4 C, 5% Si. During these studies a laser beam power of 600 W and variable scanning speed 600 mm/min, 800 mm/min and 1000 mm/min were used. Thickness and microhardness of coatings were investigated and relationship between these properties and microstructure of the applied production parameters were described. The microstructure of producing coatings was characterized by dendritic shape. It was found that boron carbide particles and silicon particles have significant influence on increase the microhardness of produced coatings. Coatings were produced using the prepared powder mixture allowed to obtain more than twice greater microhardness than in case of coatings produced using only the Fe-B powder. Phase composition was examined by XRD. Phases of Fe 3 B, Fe 5 Si 3 , Fe 2 Si and SiB 6 were identified. The influence of B 4 C and Si particles in the mixture of powder on the corrosion resistance of produced coatings were discussed. It was found gradual reduction of corrosion resistance with decreasing scanning speed of laser beam. Less scanning speed result in less intense interaction of laser beam on the material. As a result of this, the remelting degree of powder material with steel substrate was smaller. The surface condition after corrosion tests were examined using a scanning electron microscope. This paper also shows a calculation related to the power density of the laser beam, interaction time of beam on material and fluence.