Crystallographic insights into the role of nickel on hardenability of wear-resistant steels

•Revealing the role of nickel on hardenability by visualization and digitization of variants.•Increased nickel modified the variant paired mode and enhanced the hardenability.•Variant paired mode shifted from Bain grouping to CP grouping by increased nickel.•Microstructure with high density of block boundaries contributed to high hardness.•Increasing nickel content promoted to form high density of block boundaries. Two wear-resistant steel plates with different Ni content were studied to reveal the significant role of Ni on hardenability from the perspective of crystallography. From the surface to the quarter, and then to the center of the plates, the 0.44Ni steel exhibited higher hardness compared with the 0.02Ni steel, indicating that the 0.44Ni steel was of higher hardenability. The microstructure at the center changed from granular bainite to lath bainite with increased Ni content, together with an enhanced density of block boundaries. Ni improves the hardenability by weakening the variant selection through inducing larger transformation driving force and more self-accommodation of transformation strain to obtain a high density of block boundaries.