High-performance ceramic layers produced by h-graphite-assisted pulsed-DC powder-pack boriding

This study investigates the application of pulsed-DC powder-pack boriding (PDCPB) to AISI H13 steel using a novel h-graphite-containing powder mixture (GIS-T), as well as the effect of a subsequent double-tempering treatment. Microstructural and chemical analyses by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and x-ray diffraction revealed the preferential formation of Fe2B, with partial suppression of the brittle FeB. The as-borided condition exhibited practical adhesion values almost three times higher than those reported for conventionally borided AISI H13 steel with comparable ceramic layer thickness. Double tempering promoted a thinner boride layer and encouraged the dissolution of the diffusion zone; despite the reduced thickness, the borided + double-tempered condition increased the load-bearing capacity before delamination by 12% compared with the as-borided condition and achieved adhesion values slightly higher than those reported for conventionally borided steels. Using TiN coatings deposited by Physical Vapor Deposition on AISI H13 steel as an industrial benchmark, both PDCPB-treated conditions exhibited practical adhesion values approximately twice as high as those reported for this widely used automotive forming-tool coating.