Abstract
In this study, different amounts of tantalum carbide (TaC) powders (10, 20 and 30 mass%) were mixed and added to 440C steel powders. The composite powders were sintered at 1270, 1280 and 1290°C, respectively, for 1 h. The experimental results showed that a suitable amount of TaC particle addition was effective in improving the strength and hardness of the composite materials. Conversely, excess TaC hindered the liquid diffusion of the Fe elements. As a result, the 440C specimens with 30% TaC addition still had 1.3% porosity. The 440C specimens with 10% TaC addition sintered at 1270°C possessed the highest TRS values (2260.3 MPa), while those with 20% TaC addition sintered at 1290°C had the highest hardness values (HRA 85.2). The microstructural evaluation of the 440C specimens with 10% TaC addition revealed that all the rod-shaped M7C3 carbides transformed to M23C6 carbides and precipitated within the grains as a strengthening phase after heat treatment, which was advantageous to the transverse rupture strength (TRS). Consequently, the TRS value of the 440C specimens with 10% TaC addition was significantly increased (2260.3 → 2458.4 MPa) after heat treatment, thus possessing a high hardness (HRA 83.8).
