Most important properties for high temperature Titanium alloys are high specific strength, strength divided by density. Maximum service temperature of Titanium alloys is mostly limited by the creep and oxidation resistance. Today’s Titanium alloys are specified for a maximum service temperature of 600°C. However they are used typically for temperatures around 540°C because the parts have a service time of several thousand hours. High temperature Titanium alloys are also in use for Valves in high performance engines. The exhaust valves run at 820°C but with significant less service time compared to aerospace application. Recently some new high temperature Titanium alloys contain rare-earth element dispersoids to improve creep resistance. On the other hand these dispersoids could be a source for a crack. The research is ongoing to optimize the composition and behavior.
Significantly higher creep and oxidation resistance show intermetallic Titanium alloys. There are many types of intermetallic phases. From most interest currently are TiAl, Ti2AlNb, Ti3Al and Al3Ti. Most research has been done on TiAl. This intermetallic phase shows excellent creep and oxidation resistance, high fatigue strength, high modulus and low density. However the major breakthrough has not been reached yet because of the comparable low ductility. Current third generation TiAl alloys show some improvement.
Then intermetallic phases Ti2AlNb and Ti3Al have a higher density but significant higher ductility and strength. This makes both phases form interest for the replacement of Nickel based Superalloys. Compared to conventional Titanium alloys the two phases could be used for much higher service temperatures.
The con and pro of each Titanium alloy class is described within the data sheets. If you need assistance, contact us.
This Titanium alloy could be used up to 620°C for long service times. This alloy shows one the highest creep resistance of high temperature Titanium alloys. This feature makes Ti-SF61 very attractive for compressor blades. The fatigue strength is very high up to 820°C. This is very important for automotive exhaust valves. Ti-SF61 clearly outperforms most of the other high temperature alloy at high temperature fatigue resistance.
Ti-SF60 could be used up to 600°C for long service times. Ti-SF60 contains rare-earth elements for high temperature creep resistance. This alloy show excellent creep resistance and strength. Ti-SF60 is extensively tested and specified for compressor discs and blades. Ti-SF60 is a good choice for automotive application like Inlet and Exhaust valves.
AMT can supply forged discs for machining compressor discs and BLISKS.