Method for preparing single crystal superalloy test bars by using ni-w heterogeneous seed crystal

A method for preparing single crystal superalloys by using a Ni—W heterogeneous seed crystal, comprising:

• step 1, preparing a shell mould;
• step 2, preparing a seed crystal for preparing Ni—W heterogeneous single crystal test bars:
• preparing a single crystal test bar by a grain selection method;
• step 3, preparing a first Ni—W heterogeneous single crystal test bar with a [001] orientation which deviates from the axial direction by 0-12°:
• preparing a Ni—W heterogeneous single test bar with a [001] orientation which deviates from the axial direction by 0-12° by using the seed crystal obtained in step 2;
• step 4, preparing a first single crystal superalloy test bar:
• cutting the obtained first Ni—W heterogeneous single crystal test bar to obtain a Ni—W heterogeneous seed crystal that can be put into the shell mould;
• preparing a single crystal superalloy test bar by using the cut Ni—W heterogeneous seed crystal, specifically comprising:
• putting the obtained Ni—W heterogeneous seed crystal into the corundum tube in the shell mould;
• placing the shell mould filled with the Ni—W heterogeneous seed crystal in a directional solidification furnace;
• putting a purchased superalloy master alloy block into an electromagnetic melting crucible at the upper part of the furnace;
• heating the directional solidification furnace to a temperature of 1550° C. at a rate of 10° C./min, so as to melt the upper surface of the Ni—W heterogeneous seed crystal near the heater of the directional solidification furnace;
• increasing the power of the electromagnetic melting crucible to 7.5 kW, so as to completely melt the superalloy master alloy block in the crucible to obtain a superalloy liquid;
• casting the superalloy liquid into the shell mould, and full filling the shell mould with the superalloy liquid;
• generating a mushy zone with a length of 2-3 mm on the upper part of the Ni—W heterogeneous seed crystal by the cast superalloy liquid and holding for 10 min-30 min, wherein the mushy zone is a solid-liquid two-phase region generated at the joint of the superalloy liquid and the Ni—W heterogeneous seed crystal;
• after the holding is completed, subjecting the obtained system to a crystal pulling by pulling down at a rate of 40 μm/s-100 μm/s;
• after the crystal pulling is completed, taking out the product after the heating furnace is cooled to 300° C., to obtain a first single crystal superalloy test bar with a [001] orientation which deviates from the axial direction by 0-12°;
• step 5, recovering the seed crystal for reuse:
• recovering the Ni—W heterogeneous seed crystal for reuse from the obtained first single crystal superalloy test bar with a [001] orientation which deviates from the axial direction by 0-12°, specifically comprising:
• removing the shell mould on the obtained first single crystal superalloy test bar with a [001] orientation which deviates from the axial direction by 0-12°;
• cutting the Ni—W heterogeneous seed crystal from the first single crystal superalloy test bar with a [001] orientation which deviates from the axial direction by 0-12° after the shell mould is removed, and recovering it for reuse;
• and
• step 6, preparing other single crystal superalloy test bars:
• preparing other single crystal superalloy test bars by using the obtained recovered seed crystal, wherein the other single crystal superalloy test bars have a [001] orientation which deviates from the axial direction by 0-12°, and the specific process comprises:
• putting the recovered seed crystal into the corundum tube in the shell mould;
• placing the shell mould in a directional solidification furnace, and repeating step 4 to obtain a second superalloy test bar;
• repeating step 5 to re-obtain the recovered seed crystal;
• repeating the process of preparing the second superalloy test bar to obtain a third superalloy test bar;
• repeating the processes of recovering seed crystal and preparing superalloy test bar until the required number of superalloy test bars are obtained.