Development of Low-Nickel Superalloys for Exhaust Valves
Honda has developed, in collaboration with Hitachi Metals and Daido Steel, two types of low-nickel heat-resistant alloys for exhaust valves which are more cost effective than the conventional nickel alloys. They are NCF4015 that contains approximately 40% nickel and NCF3015 with approximately 30% nickel content. The two types of new alloys were developed based on our unique alloy design concept. Both alloys feature superb high-temperature strength and are capable of maintaining favorable material properties, even after an high-temperature exposure. The NCF4015 is compatible with the conventional Inconel 751 and 60Ni alloys in terms of high-temperature strength. The NCF3015 falls slightly behind the two metals, but overwhelms the 21-4N (SUH35) in high-temperature strength. The exhaust valves made of the two alloys developed have been used for mass production engines.