Fabrication of two-dimensional graded Al2O3-(W, Ti)C–TiN–Ni–Mo nano-composites by two-stage sintering

Abstract

In this study, we comprehensively investigate the critical role played by two-stage sintering (TSS) and two-dimensional (2D) graded structure on the sintering behavior and the mechanical properties of Al2O3-(W, Ti)C–TiN–Ni–Mo two-dimensional (2D) graded nanocomposites. It was observed that the optimal mechanical properties were achieved for tailored TSS conditions (θ1 = 1700 °C, θ2 = 1450 °C) and 2D graded structure (45°) with a hardness of 23.20 GPa, a first-layer fracture toughness of 10.56 MPa m1/2, and a flexural strength of 1005 MPa. TSS was more effective in maintaining the predesigned Ni gradient, facilitating the densification process and suppressing the grain growth, as compared to one-step sintering. The 2D graded structure played a more beneficial role in inducing residual surface compressive stress than a one-dimensional (1D) graded structure. Ceramics and metals formed a solid solution where the ceramic was in contact with the metal, which improved the fracture toughness of the 2D gradient material.