Microstructural design of hardfacing Ni–Cr–B–Si–C alloys

Abstract

This work reports the procedure for selection of alloying elements to refine the microstructure of hardfacing Ni-Cr-B-Si-C alloys by providing in situ formed nucleation agents. It is concluded that the refining element should be able to spontaneously produce precipitates at high temperatures with little solubility in their Cr-rich counterparts. After exploring the theoretical backgrounds on how to select the refining element, Nb and Zr were selected and the phase formation reactions of Zr-or Nb-modified Ni-Cr-B-Si-C alloys were calculated using Thermo-Calc Ò simulations. Detailed microstructural analyses of the rapidly solidified samples deposited from the modified alloys showed that addition of Nb in specific quantities induces a significant microstructural refinement in the original Ni-Cr-B-Si-C alloy without deteriorating its high hardness. The Nb-modified alloy could be used to further investigate the viability of microstructural refinement as an effective toughening mechanism for Ni-Cr-B-Si-C and similar alloy systems.

Development of volume deposition on cast iron by additive manufacturing

“…The cracking in the deposits was attributed to the formation of Cr rich precipitates and the continuous network of eutectic formation [8]. The Cr rich boride phases are brittle and crack due to the solidification stresses induced during the rapid cooling [9][10][11]. Increasing the Ni content leads to crack deflection and bridging.…”

In-situ synthesized Ni–Zr intermetallic/ceramic reinforced composite coatings on zirconium substrate by high power diode laser

“…In addition, the decomposition of WC added into powders at high temperature could not be neglected [19]. Hemmati et al [20,21] evaluated the viability of microstructural refinement as a toughening mechanism of Ni-Cr-B-Si-C coatings and pointed that both the hard precipitations and modification of the eutectic structures could improve toughness. Some transition metal elements (especially Zr, Nb) satisfied the rules proposed by Hemmati et al [20] for selecting refining elements suitable for Ni-Cr-B-Si coatings.…”

Characteristics of Thermally Sprayed Nicrbsi Coatings before and after Electromagnetic Induction Remelting Process

“…Thermally sprayed coatings offer a practical and economical solution to improve corrosion and wear resistance on these types of elements [1,2]. Nickel based hard materials, such as NiCrBSi family; have been recently used in industries where corrosion and wear resistance is strongly required like: paper, petrol, hot working punches or heat exchangers [3][4][5][6]. Many studies showed that these coatings are an alternative for hard chromium coatings, which are harmful to the environment [7].…”