INVESTIGATION OF CORROSION AND MICROSTRUCTURE PROPERTIES OF GRAY (LAMELLITE GRAPHITE) CAST IRON COATED WITH HVOF METHOD

摘要

In this study, gray (lamel-graphitic) cast-iron was coated by HVOF method using mixtures of CoNiCrAlY, NiCrBSi, WC-Co (88/12) and MoNiCrBSiFe (Mo 25%) powder. Brake discs used in today's automobiles were selected in the study. Disc surfaces were made of four-headed ceramic powder mixes, keeping the parameters of the HVOF method constant, resuhing in a coating thickness of 1 mm on the surface. Samples were made in the corrosion analysis (0.5 mol NaCl) solution. Microstruc-ture characteristics were analysed by Scanning Electron Microscope (SEM) images. Microhardness values were measured from the coating surface to the centre. As a result, the highest hardness value of 793.65 HV was formed in the NiCrBSi ceramic coating. The lowest corrosion resistance (KOHMs) was found at WC-Co ceramic coating as 0.7559.