CONTROL OF DIRECTIONAL SOLIDIFICATION PROCESS FOR PRODUCTION OF GAS TURBINE BLADES.

One of the most recent methods of producing gas turbine blades is by controlled directional solidification of superalloys.The shape and orientation of the solidified phases,which determine the required mechanical behaviour of the blades are controlled by the growth conditions. These conditions are mainly the shape,position of the solid front as well as the growth rate (R) and temperature gradient (G).The parameter G/R determines the type of structure and a minimum(or critical) value should be obtained according to the alloy composition. In the present wotk,the growth conditions are determined using numerical simulation of heat flow during solidifica-tion.A two dimensional heat flow model was set and sol"ed numerically using a finite difference technique.The effect of the process variables Withdrawal speed,furnace temperature,starting baffle positioh,heat resistance at metalchill interface_on the growth parameters are studied.The conditions for obtaining a high G/R value are found.The computer program was used to find the suitable conditions to reduce the total solidification time and to reduce large variations in growth conditions.