The Unique Influence of Boron Microalloying on Tensile Properties in a Ni‐Co‐Cr‐Based Superalloy

This work systematically investigated the tensile deformation and fracture behaviors of a Ni‐Co‐Cr‐based superalloy in the temperature range from room temperature to 1000°C through tensile performance tests at different temperatures and corresponding microstructure characterization on the alloys with and without boron (B) microalloying, revealing the effects and mechanisms of B microalloying at different temperatures. The mechanical behavior of the alloy shows distinct thermal sensitivity. Ultimate tensile strength (UTS) declines gradually below 600°C but sharply above this threshold. Yield strength (YS) decreases slowly below 900°C and drops abruptly beyond it. Below 700°C, B microalloying marginally improves YS but hinders work hardening, reducing UTS. Between 700°C and 850°C, B has a negligible effect on strength but enhances ductility by strengthening grain boundaries. Above 900°C, B exacerbates strain localization and slightly reduces YS. B microalloying induces a transition in deformation mechanisms from planar to wavy slip at low temperatures, thereby inhibiting dislocation multiplication and reducing strain hardening effects. Therefore, the role of B microalloying shifts from promoting ductility at intermediate temperatures to exerting a detrimental effect at ultrahigh temperatures.