GTAW-pulsed refusion patterns of NiCrBSI thermal sprayed coatings

Abstract

NiCrBSi coatings were produce by Flame Spray on a carbon steel substrate. The “as spray” coatings were refused by means of Pulsed Gas Tungsten Arc Welding (GTAW-P) process, following different patterns and welding procedure, with objective of optimize the coating characteristics and productivity. The patterns evaluated were oscillated triangular (OT) and oscillated sinusoidal (OS). Travel speed and distance workpiece-electrode were also analyzed. On each obtained sample the surface appearance, macro and microstructure on transverse cuts were evaluated, determining penetration, dilution and level of defects, among others features. Microhardness profiles and adherence were also evaluated. The OS pattern show a more uniform profile of the refused thickness, with less dilution with the base material. Travel speed and workpiece-electrode distance have both significant effect on the volume of refused material, affecting dilution and consequently the resultant coating hardness.