Turbine airfoil to shroud attachment method

A method comprising:

• providing a turbine airfoil comprising an end portion;
• forming a fugitive coating on at least a portion of the airfoil end portion;
• bi-casting a platform onto the airfoil end portion over the fugitive coating;
• bringing the airfoil end portion and the platform to a common temperature, thereby causing differential shrinkage stress there between;
• and
• reducing the differential shrinkage stress by removing at least a portion of the fugitive coating.

A method comprising:

• forming a turbine airfoil with an end portion, wherein the end portion comprises:
• a taper that reduces the airfoil distally;
• a ridge with a proximal side and a distal side relative to the airfoil;
• forming a coating of a fugitive ceramic material on the airfoil end portion;
• limiting the coating to a leading edge, a suction side, and a trailing edge of the airfoil end portion;
• bi-casting a platform onto the airfoil end portion of the turbine airfoil;
• wherein the fugitive coating varies in thickness in proportion to a variation in differential process shrinkage between the airfoil and the platform around the airfoil end portion;
• bringing the airfoil end portion and the platform to a common temperature;
• removing the coating of fugitive ceramic material.