The　evolution　of　the　microstructure　and　the　kinematic　model　during　solution　treatment　of　a　powdered　metallurgical　Ni-based　material　were　investigated　in　this　work.　The　results　showed　that　the　solvus　temperature　of　the　γ′　phase　was　as　high　as　1170　°C–1200　°C.　An　improved　JMAK　model　was　used　to　describe　the　γ′　dissolution　behaviour　over　a　continuous　temperature　range.　In　the　model,　the　constants　were　regarded　as　the　equations　for　temperature,　and　the　correlation　coefficient　R　was　0.9994.　The　grain　growth　behaviour　below　1200　°C　was　different　from　that　above　1200　°C;　therefore,　the　raw　material　was　well　understood　with　a　segmented　model,　and　R　was　0.9771.　During　the　cooling　stage,　as　the　cooling　rate　was　increased,　the　size　of　γ′　decreased　quickly　at　the　beginning　and　then　entered　a　stable　phase;　finally,　it　exhibited　secondary　reduction.　As　the　γ′　size　decreased,　the　hardness　of　the　alloy　first　increased　and　then　changed　slowly.　A　cubic　polynomial　was　established　to　calculate　the　size　of　γ′　at　different　cooling　rates,　and　R　was　0.97367.　A　new　hardness　prediction　model　was　used　to　predict　the　hardness　with　different　values　of　γ′　for　the　alloy,　and　R　was　0.9710.　©　2023