Microstructure characterization and mechanical properties of Cr‒Ni/ZrO2 nanocomposites

The microstructure and mechanical properties of Cr-Ni steel and Cr-Ni steel-matrix nanocomposites reinforced with nano-ZrO2 particles were investigated in this study. Cr-Ni steel and Cr-Ni/ZrO2 nanocomposites were produced using a combination of high-energy ball milling, pressing, and sintering processes. The microstructures of the specimens were analyzed using EDX and XRD. Compression and hardness tests were performed to determine the mechanical properties of the specimens. Nano-ZrO2 particles were effective in preventing chrome carbide precipitate at the grain boundaries. While t‒ZrO2 was detected in Cr-Ni/ZrO2 nanocomposites, m‒ZrO2 could not be found. Few α'‒martensite and deformation bands were formed in the microstructures of Cr-Ni/ZrO2 nanocomposites. Although nano-ZrO2 particles had a negligible impact on the strength improvement provided by deformation-induced plasticity mechanisms in Cr-Ni/ZrO2 nanocomposites, the mechanical properties of Cr-Ni steel were significantly improved by using nano-ZrO2 particles. The hardness and compressive strength of Cr-Ni/ZrO2 nanocomposite were higher than those of Cr-Ni steel and enhanced as the weight fraction of nano-ZrO2 particles increased. Cr-Ni/ZrO2 nanocomposite with 5wt.% nano-ZrO2 particles had almost twofold the hardness and compressive strength of Cr-Ni steel. The nano-ZrO2 particles were considerably more effective on particle-strengthening mechanisms than deformation-induced strengthening mechanisms in Cr-Ni/ZrO2 nanocomposites.