Effect of niobium on microstructure-property relationship in H11 hot-work tool steel via wire- and powder-based laser metal deposition

This paper presents an effect of niobium (Nb) on the microstructure-property relationship in H11 hot-work tool steel. Various amounts of Nb powder were introduced into the molten pool of H11 wire through a novel wire- and powder-based laser metal deposition (WP-LMD) process. With the increase in Nb content up to 3.45 wt.%, the average grain size of H11 decreased from 14.3 µm to 2.83 µm, while the average Vickers microhardness decreased from 706 HV0.2 to 301 HV0.2. The critical amount of Nb was then found to be 1.73 wt.%, which produced a hard (average hardness of 606 HV0.2), and refined (average grain size of 3.01 µm) microstructure of H11. Such kind of microstructures can assure high toughness and high hardness; hence more suitable for hot-working industries such as die and mould, forging and cutting tools.