Turbine blades, turbine assemblies, and methods of manufacturing turbine blades

A turbine rotor comprising:

• a rotor;
• and
• a plurality of blades extending radially outwardly from the rotor, each blade comprising:
• a first side wall including a first tip edge,
• a second side wall opposite the first side wall and including a second tip edge,
• a tip wall extending between the first side wall and the second side wall, the tip wall being recessed from the first tip edge of the first side wall and the second tip edge of the second side wall to form a coolant cavity, a tip recess cavity, a first parapet wall on the first side wall, and a second parapet wall on the second side wall, the coolant cavity defined in part by an interior surface of the tip wall, and the tip recess cavity defined, in part, by a surface of the tip wall, the first parapet wall, and the second parapet wall,
• a step formed between the first tip edge and the tip wall, and
• a cooling hole extending through the first parapet wall, the step, and the tip wall, the cooling hole including an open channel section and a closed channel section, the open channel section extending from the first tip edge of the parapet wall to the step, and the closed channel section extending through the step and the tip wall.

A method of manufacturing a turbine blade comprising:

• casting a blade including a first side wall including a first tip edge, a second side wall opposite the first side wall and including a second tip edge, and a tip wall extending between the first side wall and the second side wall, the tip wall being recessed from the first tip edge of the first side wall and the second tip edge of the second side wall to form a coolant cavity, a tip recess cavity, a first parapet wall on the first side wall, and a second parapet wall on the second side wall, the coolant cavity defined in part by an interior surface of the tip wall, and the tip recess cavity defined, in part, by a surface of the tip wall, the first parapet wall, and the second parapet wall;
• forming a step between the first tip edge and the tip wall;
• and
• machining a cooling hole into the blade, wherein the cooling hole extends through the first parapet wall, the step, and the tip wall, the cooling hole includes an open channel section and a closed channel section, the open channel section extends from the first tip edge of the parapet wall to the step, and the closed channel section extends through the step and the tip wall.