Hot isostatic pressing process for superalloy powder

Abstract

Hot isostatic press (HIP) process for superalloy powder, to form a superalloy member. A first step HIP temperature is higher than an initial melting temperature of low-melting-point alloy powder and more than 15° C. lower than a solidus of completely homogenized alloy. Pressure is ≧90 MPa, and time is 20 minutes≦t≧1 hour. Heating is stopped after the first step to cool material until temperature is below initial melting temperature of low-melting-point phase. There is temperature keeping for ≧2 hours, to ensure low-melting-point phase, formed during cooling after first step, is completely dissolved. Alloy is cooled after second step to room temperature as furnace pressure keeping continues. Formation of an original particle boundary is prevented or there is significantly reduced the number of precipitated phases on the original particle boundary in HIP procedure, to obtain compact alloy with microscopic structures as equiaxed crystals.

1 . A hot isostatic pressing method for superalloy powder, which is characterized in that:
 the process comprises the following steps:   (1) preparing superalloy powder by gas atomization or other methods; sieving the powder to obtain the powder with size less than or equal to 155 μm; loading the sieved powder into a carbon steel or stainless steel capsule; hot degassing and then sealing the capsule;   (2) putting the powder capsule prepared in step (1) into a hot isostatic pressing apparatus; starting hot isostatic press compaction after reaching the presupposed conditions in a manner of heating and pressuring simultaneously or heating firstly and then pressuring;   wherein the parameters for the hot isostatic press are: the hot isostatic pressing temperature is within the range between the incipient melting temperature of the low-melting-point phase in the powder particles and the solidus of completely homogenized alloy plus 15° C.; the pressure is higher than or equal to 90 MPa; the holding time in this stage is longer than or equal to 20 minutes and shorter than or equal to 1 hour when the temperature in the furnace reaching the presupposed temperature;   (3) stop heating when the holding process of step (2) is finished, cool the capsule in the furnace to temperature that is below the incipient temperature of the low-melting-point phase in the powder particles and then hold at that temperature, the holding time for this stage is 2 hours or longer to ensure that the low-melting-point phase formed during cooling can be completely dissolved and the pressure in the temperature keeping process is higher than or equal to 90 MPa; stop heating and cool the capsule in the furnace to room temperature when this holding process is finished.   
     
     
         2 . The hot isostatic pressing method for superalloy powder according to  claim 1 , which is characterized in that: the method is applicable to hot isostatic pressing consolidation of nickel-iron-based superalloy powder or nickel-based superalloy powder. 
     
     
         3 . The hot isostatic pressing method for superalloy powder according to  claim 1 , which is characterized in that: in step (1), the size of the sieved powder particles is less than or equal to 105 μm. 
     
     
         4 . The hot isostatic pressing method for superalloy powder according to  claim 1 , which is characterized in that: in step (1), the size of the sieved powder particles is less than or equal to 55 μm. 
     
     
         5 . The hot isostatic pressing method for superalloy powder according to  claim 1 , which is characterized in that: for GH4169 and derived alloys powder thereof, the incipient melting temperature of the low-melting-point phase is the Laves-phase incipient melting temperature of GH4169 and derived alloys thereof; and for other γ′-phase strengthened nickel-base superalloy powder, the incipient melting temperature of the low-melting-point phase is γ/γ′ eutectic temperature. 
     
     
         6 . The hot isostatic pressing method for superalloy powder according to  claim 1 , which is characterized in that: in step (2), the range of hot isostatic pressing pressure is 120 MPa to 150 MPa. 
     
     
         7 . The hot isostatic pressing method for superalloy powder according to  claim 1 , which is characterized in that: in step (3), the range of pressure in the temperature keeping process is 120 MPa to 150 MPa. 
     
     
         8 . The hot isostatic pressing method for superalloy powder according to  claim 1 , which is characterized in that: in step (2), when the hot isostatic pressing temperature is higher than the incipient melting temperature of the low-melting-point phase of alloy powder and lower than the solidus of completely homogenized alloy, this method can reduce the amount of precipitates along the prior particle boundary. 
     
     
         9 . The hot isostatic pressing method for superalloy powder according to  claim 1 , which is characterized in that: in step (2), when the hot isostatic pressing temperature is higher than the solidus of completely homogenized alloy and lower than solidus of completely homogenized alloy plus 15° C., this method can eliminate or avoid the formation of prior particle boundary.