2014 Volume 55 Issue 11 Pages 1755-1761
This study explored a series of HIP processes, solution heat treatments and aging treatments, in which various amounts of tantalum carbide (TaC) powder are added for sintering cobalt-based composite materials. Experimental results showed that the highest transverse rupture strength (TRS) of 1812.4 MPa was obtained by the 10 mass% TaC added to cobalt-based alloys, which was sintered at 1270°C, and followed by HIP processes, solution heat treatments, and aging treatments for 12 h. The hardness increased to 80.1 HRA. In addition, the added amounts of TaC powder and aging times played important roles in improving the mechanical properties of the cobalt-based alloys. By microstructural observations, it was found that both M6C and M23C6 carbides precipitated in the matrix of the 0% TaC specimens after various aging treatments. However, the more refined and uniform precipitations of M6C, M23C6 and MC carbides were precipitated in the matrix of the TaC powders added to cobalt-based alloys after 12 h of aging treatment at 850°C. This result was effective in improving the mechanical properties of the cobalt-based alloys. Conversely, 15 h of aging treatment at 850°C generated an over-aging phenomenon, which resulted in a decrease in TRS value.