In the current period, gas turbines are one of the most reliable choices available for power generation worldwide. Statistically, it is forecasted that the gas turbine market value can grow and cross $20 billion by 2021. Moreover, the usage rate of gas turbine parts and services is expected to continue the upward increase in the future. Here, the components that operate gas turbines are important to note and consider seriously, specifically the high-temperature materials.
Typically, highly efficient gas turbines, as well as jet engines that have enhanced operating temperatures, release lower CO2 emissions. This is healthier for the global population; thus, it is important to focus on improve high-temperature material properties. In this article, you would get a more in-depth focus on the different high-temperature materials available for gas turbine operation. Not to mention, it details the potential future of these materials in the market as well.
Advancements in high-temperature materials
Gas turbine specialists utilize many types of Ni-base superalloys for the high-temperature components, such as high-pressure turbine vanes and blades, and combustors. To note, out of the different superalloy types, single crystal (SC) superalloys can withstand the highest rate of temperature.
At the current time, third-generation SC alloys are utilized commonly in jet engines and industrial-level gas turbines. Additionally, the fourth-generation SC alloys mixed with metals in the platinum group are under development. In terms of gas turbines specifically, the SC superalloys are very helpful for improving thermal efficiency via higher inlet gas temperatures.
Besides the SC superalloy, other materials that can withstand higher temperatures are still under R&D in the market. These include refractory alloys, intermetallic alloys, and ceramics. In particular, many manufacturers utilize bulk ceramics with a silicon nitride base for gas turbine-based power generation. Moreover, many operators are depending on oxide-based and non-oxide-based ceramic matrix composites.
Typically, ceramics are useful for structural application as well as for coating in gas turbines. Two notable ceramic matrix composite-based options for gas turbine operation protection that you must consider are environmental and thermal barrier coatings.
Best high-temperature material choices
It is useful to go for composite materials with two or more components, each of them having different properties. This forms a material that is resistant to very high temperatures and can run generators for a long period. The main two types of combined composite materials best for gas turbines are as follows.
Metal matrix composites (MMCs)
These metal alloys possess a ductile metal matrix. There are fibers or particles with high-temperature resistance properties spread within the materials. Among them, those with intermetal phases are the best high-temperature materials suitable for gas turbine operations. Overall, there are multiple types available here that works with different turbine types as well as turbine parts.
Firstly, the molybdenum-based alloys that contain silicide particles are commonly used in many power plants. Currently, the latest version is still in the research and development phase and is expected to launch in the near future. The constituent has a very high melting point, at 2617°C. Moreover, it is expected the Mo-Si-B alloy can operation the turbine engines at high temperatures than most current components.
While the allow can withstand very high temperatures, cold temperature is a major weakness. At low temperatures, the alloys get brittle which makes it difficult to compose an appropriate shape for the material.
A lot of gas turbine types currently available worldwide adopt MMCs types for machine operations. To note, metals like rhenium or niobium are similar to molybdenum. They can mix with cobalt or silicon to form high-temperature resistant MMCs, but suitable for particular situations.
Compared to available options, the iron aluminide-based alloys suit parts that run at low temperatures. These alloys are less costly and lighter as well and are often used in steam turbines. Moreover, structural applications that require stainless steel components and reach 1000°C can utilize these materials.
Another notable type is vanadium silicide alloys that can reach around 1000°C temperature and has a very low density. Moreover, titanium alloys provide multiple mechanical properties; they are commonly used in biomedical, petrochemical, and aerospace industries. Also, such alloys match well with many processing parameters during additive manufacturing processing.
To note, in the future, intermetals like titanium silicide and titanium carbide would have a higher rate of usage with low-density applications. This is common for aerospace components. In fact, manufacturers utilize titanium aluminides in some commercial aircraft engine parts at the time.
Ceramic matrix composites (CMCs)
Until recently, CMCs were mainly under R&D; however, they will be used in gas turbine high-temperature materials soon. They are highly resistant to high temperatures and have suitable mechanical properties. Compared to MMCs, these components have low weight, around one-third of the nickel-based superalloy weight.
Currently, Silicide Carbide (SiC) CMSs are under usage in the jet engines of some commercial aircraft. Also, CMCs are more commonly used in parts that do not operate with high mechanical properties, like shrouds and nozzles. However, multiple manufacturers are considering adding these CMCs in blade components in the future.