About
Hite Special Alloy is a high-tech enterprise, mainly engaged in the production of Hastelloy, Monel, Inconel, nickel and other high-temperature alloys.
Overview of IN738LC alloy
IN738LC alloy is typical γ Phase precipitation strengthened nickel based high-temperature alloy, with a variety of phase types and alloying elements, has excellent high-temperature endurance performance, good corrosion resistance, fatigue resistance, and other characteristics. It is widely used in hot end components such as ships, industrial gas turbines, and aviation engines with operating temperatures below 900 ℃. Especially in high temperature and complex stress conditions, its price is usually very expensive.
Introduction to Inconel738 nickel based high-temperature alloy
IN738 alloy (full name Inconel 738) is a precipitation strengthened nickel based high-temperature alloy developed by Licenses of International Nickel in the United States, which contains insoluble elements such as Mo, W, Ta, Nb, etc. This alloy is subject to Solid solution strengthening of Mo, W and Cr dissolved into the matrix, precipitation strengthening of intermetallics Ni ≮ (Al, Ti) and grain boundary strengthening of metal carbides (Ti, Ta, Nb) C, showing high oxidation resistance, corrosion resistance and creep resistance. Therefore, it has long been used in the manufacturing of turbine heat and corrosion resistant parts in petrochemical industry and aerospace industry. According to the different carbon content, IN738 has two improved alloys, one is a low-carbon IN738LC alloy, and the other is an ultra-low-carbon IN738FC alloy.
Generally speaking, the INCONEL alloy series has the following characteristics:
High temperature strength: INCONEL alloy maintains high strength in high-temperature environments and has excellent oxidation and creep resistance.
Corrosion resistance: INCONEL alloy has good resistance to corrosion and oxidation, including resistance to acid, alkaline, and salt corrosion.
Thermal expansion: INCONEL alloy has a low coefficient of thermal expansion and can maintain relatively stable size in high-temperature environments.
Timeliness treatment
High temperature alloy aging treatment, sometimes also known as precipitation treatment, aims to precipitate a certain amount and size of strengthening phases in the alloy matrix, such as γ' Phase γ Equal to achieve the maximum strengthening effect of the alloy [57]. Usually, as the content of alloying elements in the alloy increases, the aging temperature of the alloy also increases, especially with the increase of tungsten, aluminum, nickel, molybdenum, and titanium content, with a minimum temperature of 650 ℃ and a maximum temperature of 980 ℃ l58. Some alloys should have their aging temperature changed to suppress σ、μ Wait for the precipitation of some harmful phases. Generally speaking, the aging temperature is the main temperature at which alloys are used. In order to adjust the size of strengthening phases in some high-temperature alloys, some high-temperature alloys are divided into two stages of aging to obtain more suitable strength and plasticity. The strengthening phase of most high-temperature alloys is γ' The size and quantity of phase and y phase have a significant impact on the degree of strengthening [59], therefore aging treatment plays a crucial role in the strength of the alloy.
IN738LC solid solution treatment
(1) After solid solution treatment at different temperatures and holding times, as the temperature and holding time increase.
In addition, the grain size of the XOY surface increases accordingly, but there is little change in size after 1230 ℃. The grain size of the XOZ surface transforms from coarse and long columnar grains to equiaxed grains. Overall, by comparing the grain size and equiaxation degree, the solid solution temperature at 1230 ℃ has the best effect.
(2) After different solid solution treatment, intermediate treatment, and aging treatment, it was found that different morphologies precipitated between different grains γ' Phase. As confirmed, γ' The difference in phase morphology occurs after intermediate treatment, and after intermediate treatment, there are large and irregular precipitates on the grain boundaries γ Phase and M ₂Å C ₆ type carbides.
(3) By comparing the tensile mechanical properties at high temperature, it is found that the SLM formed IN738LC alloy has undergone Hot isostatic pressing+solution treatment (1230 ℃ × 2h, furnace cooling)+intermediate heat treatment (1120 ℃ × 2h, furnace cooling)+aging treatment (900 ℃ × After 24 hours of composite treatment with air cooling, the comprehensive high-temperature mechanical properties of the material are the best. At 1000 ℃ σ B is 375MPa horizontally and 385MPa longitudinally, and c Å is 260MPa horizontally and 259MPa longitudinally, respectively, δ They are 7% horizontally and 11.1% vertically, and u is 5.5% horizontally and 13% vertically, respectively; At 1100 ℃, except for a slight increase in longitudinal section shrinkage, all other indicators showed a significant decrease, among which σ B is 149MPa horizontally and 153MPa vertically, while cs is 84MPa horizontally and 100MPa vertically, δ 5.5% horizontally and 9.91% vertically, respectively, ψ 5% horizontally and 15% vertically, respectively.
