SU1077700A1 - Method of hot isostatic compacting of powders of titanium alloys - Google Patents

Abstract

) A METHOD OF HOT ISOSTATIC PRESSING TITANIUM ALLOYS POWDERS, including heating the powder to a temperature of 20-40 ° C; C below the temperature of the polymorphic transformation of the alloy with simultaneous pressure increase, storing and cooling of d0 at room temperature, characterized in that, in order to increase the performance of short-term strength at room and elevated temperatures, cooling is carried out at a rate of 0.5-1.5 "C / with,

Description

The invention relates to powder metallurgy, in particular, to methods for producing preforms or articles from metal powders while conducting a compaction and sintering process. The known method of hot isostatic pressing of a powder of titanium alloy in a gas combustor is that the metal powder is placed in capsules and compacted at a pressure of 2000 atm for 1 hour. Cooling is performed at a speed of 0.050, 07 C / s G13 . The disadvantage of this method is the comparatively low short duration of strength at room and elevated temperatures of the obtained billets (below the short term strength of the material obtained by the deformation of the ingot) and the low productivity of the process due to the duration of cooling in the gas chamber. The closest to the proposed method to the technical essence and the achieved result is the method of hot isostatic pressing of powders of titanium alloys, consisting in heating the powder to a temperature of 20-40 ° C below the temperature of the polymorphic transformation of the alloy previously placed in the chamber with simultaneous pressure rise , exposure under these conditions with subsequent cooling. According to this method, heating is carried out up to 954 ° C, and cooling is carried out at a rate of 0.07 ° C / sec. The disadvantage of this method is the low productivity of the process of hot isostatic pressing in a gas stove and a reduced level of short-term strength at room temperature and elevated temperatures of compact blanks due to low speed cooling equal to 0.07 s / s. The aim of the invention is to increase the productivity of the process and the short-term strength at room and elevated temperatures. To achieve the goal, according to the method of hot isostatic pressing of titanium alloys, including heating the powder to a temperature of 20-40 ° C below the polymorphous transformation temperature of the alloy with simultaneous pressure increase, exposure, cooling to room temperature, cooling is carried out at a rate of 0, 5-1,5 ° C / s. Cooling in air with a speedy 0.5-1 / 5 ° C / s after hot isostatic pressing results in the formation of an oC phase of the desired morphology and fixation of such a number of unstable (L-faea, the disintegration of which during further annealing leads to an increase in short-term strength limit at room and elevated temperature while maintaining a sufficiently high ductility. Cooling after hot isostatic pressing at a rate of less than 0 ° C / s increases the size and amount of the "st-phase due to recrystallization it reduces the short-term strength limit both at room and elevated temperatures.Cooling after hot isostatic pressing at a rate of more than 1.5 S / s leads to crushing and a decrease in the C-phase and increasing the number of unstable f-phase, which leads to an increase in the values of short-term strength at room and elevated temperatures and a significant reduction in plasticity characteristics (V | . Example 1. Capsules 270x70 mm in size made of stainless steel with granules of titanium alloys VTZ-1 and VT8, previously evacuated and sealed, are placed in a gas switch, heated to 940 and 960 s, respectively, which is 30 ° C below the temperature of polymorphic transformation of the alloys, while by raising the pressure to 160.0 atm, maintained at the specified parameters for 4 hours, then cooled at a speed of 0.5 s / s. The cycle time of hot isostatic pressing is shown in Table. 1. Short-term strength at room and elevated temperatures of compact blanks from granules of alloys BTZ-1 and VT8 are given in table. 2. PRI mme R 2. Capsules 270x60 mm in size made of stainless steel with granules of titanium alloys ZTZ-1 and VT8, previously evacuated and sealed, are placed in a gas switch, heated to 940 and 960 ° C, respectively, which is lower than the polymorphic transformation temperature alloys, with a simultaneous increase in pressure to 1600 atm., are maintained at the given parameters for 4 h, then cooled at a rate of 1 ° C / s. The cycle time of hot isostatic pressing is shown in Table. 1. Short-term strength at room and elevated temperatures of compact blanks from granules of VTZ-1 and VT8 alloys is given in table. 2

Example 3. Capsules of 200x50 mm in size made of stainless steel with granules of titanium alloys VTZ-1 and VT8, previously evacuated and sealed, are placed in a gas switch, heated to 940 and 960 ° C, respectively, which is 30 ° C below the temperature of polymorphic transformation of alloys, with a simultaneous increase in pressure to 1600 atm., maintained at the given parameters for 4 h, then cooled at a speed of 1.5 s / s.

The cycle time of hot isostatic pressing is shown in Table. one.

Short-term strength at room and elevated temperatures of compact blanks from granules of VTZ-1 alloys are given in Table. 2. h

As can be seen from the results presented in table. 1, 2 The use of the proposed method of hot isostatic pressing, which includes cooling at a rate of 0-1.5 ° C / s, improves the productivity of the process of hot isostatic pressing of granules of titanium alloys by reducing the cooling time of compact billets by an average of

1.5 h and increase the level of short-term strength at room temperature by 7-11 kgf / mm and 7 16 kgf / mm for VTZ-1 alloys and

5 VT8, respectively, and elevated temperature (450 and 500 ° C1 at 4 9 kgf / mm 2 and 9-13 kgf / mm for VTZ-1 and VT8 alloys, respectively, Table 2).

Table

1600

Famous

Suggested examples

100-103

Izvestny

Suggested examples

0.07

table 2

101-103

70-72

65-67

Claims (1)

(54) (57.) METHOD OF HOT ISOSTATIC PRESSING OF POWDERS OF TITANIUM ALLOYS, including heating the powder to a temperature of 20-40 ° C below the temperature of the polymorphic transformation of the alloy with a simultaneous increase in pressure, holding and cooling at room temperature, characterized in that , in order to increase the productivity of short-term strength at room and elevated temperatures, cooling is carried out at a rate of 0.5-1.5 ° C / s.