Hot isostatic pressing of single-crystal nickel-base superalloys: Mechanism of pore closure and effect on Mechanical properties

Abstract

Abstract. Pore annihilation was investigated in the single-crystal nickel-base superalloy CMSX-4. HIP tests at 1288• C/103 MPa were interrupted at different times, then the specimens were investigated by TEM, metallography and density measurements. The kinetics of pore annihilation was determined. The pore closure mechanism was identified as plastic deformation on the octahedral slip systems. A model describing the kinetics of pore closure has been developed on the base of crystal plasticity and large strain theory. Mechanical tests with the superalloy CMSX-4 and the Ru-containing superalloy VGM4 showed, that HIP significantly increases the fatigue life at low temperatures but has no effect on creep strength.

On the Effect of Hot Isostatic Pressing on the Creep Life of a Single Crystal Superalloys

“…However, experiments which assess the effect of HIP on the basis of tensile creep results from specimens where loading directions deviate up to 5 from the precise [001] direction must be interpreted with care. [18] The results of the present work also confirm some of the conclusions which were put forward by Reed et al [16] and Epishin et al [17] Our results confirm that HIP does not affect the general features of individual creep curves and does not strongly affect primary creep. The present work presents clear experimental evidence for a beneficial effect of HIP on the evolution of porosity, especially during low temperature and high stress creep (smaller pore volume fractions and pore sizes delay microcrack nucleation).…”

“…Most importantly, HIP treatments improve creep strength (longer rupture lives) and creep ductility (larger rupture strains). [16][17] However, these improvements are small, and therefore, from a technological point of view, it is not clear whether it is worth the effort to apply HIP treatments. Some SX processing schemes include HIP after casting, because porosity can increase in the homogenization treatment.…”

“…The results are discussed in the light of previous findings. [9][10][11][14][15][16][17][18] 2. Material and Experiments…”

Application research progress of hot isostatic pressing technology in nickel-based single crystal superalloy

“…Therefore, the hot isostatic pressure temperature should not exceed 1340°C under 150MPa to avoid the initial melting of DD10 single crystal superalloy. Inmaculada Lopez-Galilea [15] carried out a hot isostatic pressing process study on the single crystal superalloy ERBO-1 at different temperatures, pressure and holding time. The as cast sample (ERBO-1A) and the fully solution and aged sample (ERBO-1C) were selected for different hot isostatic pressing studies.…”

A Vacancy Model of Pore Annihilation During Hot Isostatic Pressing of Single Crystals of Nickel-Base Superalloys

“…The porosity in single-crystal superalloys is small and does not exceed several tenths of a percent by volume. However, it significantly reduces the fatigue strength of single-crystal superalloys in the temperature range of 20-750°C [7]; therefore, single-crystal blades are exposed to hot isostatic pressing (HIP). In spite of the industrial application of HIP, the physical mechanism of pore healing in single-crystal superalloys during the production of blades is not quite clear, which complicates the choice of technological parameters of HIP (temperature T, pressure p, and duration t), as well as the prediction of the lifetime of HIP-treated blades.…”