TY - JOUR

T1 - Effect of Nb incorporation in Mo2BC coatings on structural and mechanical properties—Ab initio modelling and experiment

AU - Zenisek, Jaroslav

AU - Soucek, P.

AU - Ondračka, Pavel

AU - Czigány, Zsolt

AU - Buršíková, V.

AU - Holec, David

AU - Balazsi, K.

AU - Vasina, Petr

N1 - Publisher Copyright: © 2024 The Authors

PY - 2024/4/15

Y1 - 2024/4/15

N2 - This article presents theoretical and experimental findings on the stability of orthorhombic (Mo 1−xNb x) 2BC phase in magnetron sputtered coatings, where molybdenum is gradually replaced by niobium. Magnetron co-sputtering of Mo 2BC and Nb 2BC targets was used to best preserve the metal/non-metal ratio of 1/1. The theoretical calculations were based on replacing Mo atoms in orthorhombic Mo 2BC cell, thus creating a (Mo 1−xNb x) 2BC solid solution. It is predicted to be stable up to 37.5% of Mo atoms replaced by Nb, at which point also the elastic modulus and the shear modulus are the highest. Simultaneously, the enthalpy of formation of this material suggests that it should be more stable than, e.g. the commonly used and studied TiAlN. Experiments have confirmed that orthorhombic (Mo 1−xNb x) 2BC does not form at high Nb contents, and fcc NbC-like structure was observed instead. All coatings were shown to be columnar with grains in the nanometre range with amorphous regions between the columns. This led to reduced stability of the orthorhombic Mo 2BC-like phase compared to the theoretical calculations. At the limit of the stability of the orthorhombic cell, the hardness of the coating was enhanced by 25% and the elastic modulus by 60%. Ab initio calculations indicate that lattice strain is responsible for the mechanical properties’ enhancement.

AB - This article presents theoretical and experimental findings on the stability of orthorhombic (Mo 1−xNb x) 2BC phase in magnetron sputtered coatings, where molybdenum is gradually replaced by niobium. Magnetron co-sputtering of Mo 2BC and Nb 2BC targets was used to best preserve the metal/non-metal ratio of 1/1. The theoretical calculations were based on replacing Mo atoms in orthorhombic Mo 2BC cell, thus creating a (Mo 1−xNb x) 2BC solid solution. It is predicted to be stable up to 37.5% of Mo atoms replaced by Nb, at which point also the elastic modulus and the shear modulus are the highest. Simultaneously, the enthalpy of formation of this material suggests that it should be more stable than, e.g. the commonly used and studied TiAlN. Experiments have confirmed that orthorhombic (Mo 1−xNb x) 2BC does not form at high Nb contents, and fcc NbC-like structure was observed instead. All coatings were shown to be columnar with grains in the nanometre range with amorphous regions between the columns. This led to reduced stability of the orthorhombic Mo 2BC-like phase compared to the theoretical calculations. At the limit of the stability of the orthorhombic cell, the hardness of the coating was enhanced by 25% and the elastic modulus by 60%. Ab initio calculations indicate that lattice strain is responsible for the mechanical properties’ enhancement.

UR - http://www.scopus.com/inward/record.url?scp=85185707679&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2024.119741

DO - 10.1016/j.actamat.2024.119741

M3 - Article

VL - 268.2024

JO - Acta materialia

JF - Acta materialia

SN - 1359-6454

IS - 15 April

M1 - 119741

ER -