The effect of microstructure on fracture mechanisms of 2.25Cr1Mo low alloy steel .B. The influence of carbides

The size and distribution of carbides in 2.25 Cr1Mo steel after different heat treatments has been studied by undertaking detailed metallographic examination and hardness testing. As expected, prolonged exposure to elevated temperature resulted in significant coarsening of the metallic carbides present. The effect of these changes in carbide size on fracture behaviour was established by undertaking a programme of miniature disk testing. Analysis of these data demonstrated that ageing increased the tendency for brittle fracture. These effects are compatible with the concept that the critical stress for brittle fracture is inversely proportional to the size of the carbides present.