A turbine blade assembly, in particular of a gas turbine, is provided. The turbine blade assembly includes a turbine disc with rotor blades inserted into notches of the turbine disc and locking plates that are placed inside circular grooves with rims in the turbine disc and in the rotor blade. The edges of the locking plates that are oriented towards the center of the turbine disc are castellated by providing teeth and accordingly a part of the rim of the circular groove of the turbine disc is also castellated by providing gaps and whereby the gaps of the rim match the teeth of the locking plates. The locking plates have a spring-back force to provide both locking and sealing capabilities during engine operation.