The influence of solution treatment on grain size and pinning effects of the second phase on grain growth in spray formed superalloy GH742y were investigated by OM, SEM, TEM, DSC, phase extraction and XRD. The results indicates that the limiting ultimate grain size is about 40 μm. The equilibrium γ′ solvus temperature is determined to be about 1130 °C. Nb- and Ti-rich carbonitrides have good thermal-stability and could hardly change in their amount, size and morphology after solution treatment at 1250 °C solution treatment for 4 h. They inhibit the grain boundary migration and grain growth, by pinning the grain boundary.