EFFECT OF PACVD TIN ON PITTING CORROSION OF HIGH ALLOYED TOOL STEEL

PACVD TiN layers formed on pre-nitrided tool steel considerably decrea se the active dissolution, hinder the pit nucleation, and eliminate th e deterioration of the steel surface in chlorine containing acid solut ion. Pre-nitriding of tool steel under glow discharge conditions provi ding the formation of a diffusion zone only, affects the structure and properties of the TiN deposit. The boundaries of grains and grain con glomerates serve as sites for pitting attack on TiN covered steel. Inc rease in the grain size and formation of conglomerates decrease the co rrosion susceptibility, however, if the conglomerate size overlaps the layer thickness, the possibility of corrosion attack increases.