Developing high strength and ductility in cobalt alloy via chromium carbonitride addition

In this study, we present a strategy for the development of cobalt alloy with high performance, by introducing a nitrogen-containing solid solution powder Cr2(C,N). Despite the cobalt accelerates the nitrogen removal from Cr2(C,N) during sintering, interestingly, nitrogen seemingly plays a pivotal role in regulating the microstructure of cobalt alloy. Detailed microstructural analyses indicate that the fcc-Co increase, CrN precipitates and finer grain size are formed within the cobalt matrix with Cr2(C,N) addition. These structural modifications significantly contribute to the strength and toughness. In comparison to the without N-doped cobalt alloy, the compressive strength undergoes a significant 34% increase, rising from 1150MPa to 1540MPa. Similarly, the bending strength exhibits an upward trend, ascending from 1605 MPa to 1766 MPa. Concurrently, the introduction of Cr2(C,N) results in an almost 80% enhancement in bending strain compared to the without N-doped one. Additionally, a notable 28% increase in hardness is obtained. The substantial enhancements in strength and toughness are mainly attributed to the combined effects of solid solution and precipitation strengthening. Our findings confirm the capability of Cr2(C,N) to the cobalt alloy reinforcement, providing valuable insights for integrating Cr2(C,N) to enhance the cobalt alloy, and laying a foundation for future investigations into the forms of nitrogen and the strengthening and toughening mechanisms of nitrogen-containing alloy. The insights gained in this study also provide novel strategies for the design of materials characterized by both needed strength and ductility, thereby advancing the development of ultra-strong and ductile materials with superior toughness.