24 April 2020, Sheffield, UK – Superalloys were developed to create components with excellent strength and creep resistance at very high temperatures.
One example of this is in the turbine wheel of an automotive supercharger where the hot and corrosive gases involved necessitate a material that carefully balances weight, strength and durability in an environment unsuited to normal metals.
When the automotive industry started to use superalloys, its engineers looked at the range of superalloys already available. These had been developed primarily for aerospace jet engines but nevertheless offered exactly the properties that were needed as they safely gave predictable operation in extreme environments, perfect for turbine wheels subject to stresses of over 600MPa and temperatures in excess of 1472°F (800°C).
For many years these superalloys, generally nickel-based alloys, have been the mainstay of turbocharger turbine production and have served the industry well. They were however designed for a different purpose; specially formulated for components operating in the extreme environment of industrial or aerospace gas turbines where creep resistance is paramount and generally over-engineered for use in a turbocharger turbine wheel where the environment is comparatively less extreme. These impressive properties come at a cost, though the full benefits aren’t seen or required by the automotive industry.
As a result, metallurgists at superalloy specialist Ross & Catherall have been working on two new bespoke superalloys especially for turbocharger turbine wheels; RCV09 and RCV11. The results are superalloys tailored to offer all of the properties that made the old superalloys an ideal solution in the first place, longevity, high temperature performance, density, oxidisation resistance, fatigue resistance, but with reduced raw material costs improving cost-effectiveness for the automotive industry.
Following the completion of rigorous tensile, stress rupture and corrosion testing, the team at Ross & Catherall are excited to introduce their new superalloys to the automotive industry and are keen to demonstrate the advantages that they bring.
Richard George, Ross & Catherall’s Technical Director explained: “Developing these alloys hasn’t simply been a case of looking at ways to make material cheaper by cutting performance. We’ve worked hard to develop superalloys tailored more closely to the environment they will be used in, so in some important areas their performance has actually been improved.
“RCV09 typically gives a 5% increase in elevated tensile stress across a typical operating temperature range of 800°C to 1100°C compared to the superalloy commonly used by the industry, whilst its density is unchanged. RCV11 gives comparable properties to the current ‘go-to’ material, but costs approximately 30% less and offers a lower density.
“Hot corrosion testing in a gasoline exhaust gas environment has shown that both RCV09 and RCV11 offer increased protection from corrosion, increasing the long-term durability and performance of turbine wheels.”
For more information about these new superalloys, contact the team at Ross & Catherall at superalloys@doncasters.com. For information about the range of Superalloys Ross & Catherall can supply visit www.rossandcatherall.com
