Effects of niobium and yttrium additions on carbide characteristics, microstructural evolution, and performance enhancement in D2 cold work die steel
Year: 2025
Type: article
Abstract: : To achieve an optimal balance between hardness and impact energy in D2 die steel, different contents of Nb and Y are added. The microstructure and mechanical properties of D2 steel in the as-cast, forged-annealed, and quenched-tempered conditions are systematically studied. The results show that the lattice mismatch between NbC and M7C3 eutectic carbide is only 0.75%, and NbC can reduce the volume fraction and size of M7C3 eutectic carbides. Y preferentially reacts with O and S to form Y2O2S and Y2S3, providing heterogeneous nucleation sites for NbC, thereby refining it. The refined NbC acts as a heterogeneous nucleation core for M7C3 carbides, indirectly improving its morphology and distribution. After forging and annealing, the carbides in 0.8Nb+Y steel exhibit the highest shape factor K. Nb suppresses the growth of secondary carbides by reducing the carbon diffusion coefficient. Y promotes secondary carbide spheroidization. As Nb content increases, the grain size and secondary carbide size in the steel decrease gradually after quenching and tempering. Y further optimizes the morphology and distribution of carbides, enhancing the microstructural uniformity. Finally, the 0.8Nb+Y steel achieves excellent hardness (62.2 HRC) and impact toughness (38.3 J).
Institution: University of Science and Technology Beijing
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,640
Awards: G1816535256, G2953051683
OpenAlex ID: W4414036774