Effects of remelting processes on porosity of NiCrBSi flame sprayed coatings

In the current study, image analysis technique was used to determine and compare the porosity level and characteristics of the pore size and shape of the flame sprayed NiCrBSi coatings before and after remelting processes. The effect of remelting temperature on the shape and size distribution was investigated by image analysis using SEM images. Remelting processes were carried out at 950, 1000, 1050 and 1100 degrees C. The obtained results revealed that remelting process decreased the porosity level (from 11.7 to 1.9%) and improved the metallurgical bonding between the carbon steel substrate and the coating. The pores shape in the as sprayed sample was an irregular, elongated shape. More than 55% of pores were sharp disc shaped. After the remelting process, the pore shape was converted to a near spherical and non-flat spheroidal configuration.