Mechanical Properties and Impact Toughness of Molybdenum Alloyed Ductile Iron

Abstract

Grades of high silicon ductile iron offer excellent combinations of static strength and ductility as well as good machinability due to their fully ferritic, solution strengthened matrix. As a result of elevated silicon contents, however, the ductile-to-brittle transition temperature in the Charpy impact test is significantly increased. Thus, minimum required Charpy impact energies cannot be met for many applications by using high silicon ductile iron. Therefore, alloys with lower strength and higher toughness properties are commonly used for many technical applications. The enormous lightweight construction potential of high silicon ductile iron can therefore not be fully exploited. The present investigation pursues the metallurgical approach of partially substituting silicon with molybdenum as an alternative strengthening element in order to improve the toughness properties while maintaining similar static mechanical properties. Molybdenum serves as a carbide-stabilising element in ductile iron, while simultaneously promoting ferrite formation and is therefore regarded to be suitable alloying element. In Charpy impact tests, the ductile-to-brittle transition temperature could be reduced by about 55 °C by reducing the silicon content to 2.95 wt% and adding 0.21 wt% molybdenum compared to a high silicon alloy. Additionally, it was possible to mathematically describe the transition behaviour of the studied alloys using nonlinear regression functions and to achieve a sufficient correlation of empirically determined and calculated data. This present metallurgical concept offers a promising metallurgical tool for further improving the toughness properties of alloyed ductile iron.

High Temperature Oxidation Behavior of High Al-Si Alloyed Vermicular Graphite Cast Iron for Internal Combustion Engine’s Hot-End Exhaust Components

“…Building on the exploration of alternatives, the addition of silicon and molybdenum as ferrite stabilizers to SiMo ductile iron has been shown to be the most effective method for improving its performance at elevated temperatures. Molybdenum improves creep resistance and machinability while diminishing toughness as a consequence of carbide segregation at grain boundaries [11][12][13]. The high silicon content increases the temperature of the ferrite-austenite transformation, which determines the maximum useful regime for SiMo nodular iron.…”

implementation of cored wire technology into production of ductile iron for castings designated for extreme conditions

“…Cast iron with spheroidal graphite is also relatively cheap [5]. Owing to its properties it is used, for example, for working machines manufacturing in automobile industry or for manufacturing of aerogenerator components [3,6]. Mechanical properties of cast iron are influenced by the graphite shape, nodularity and distribution [6,7].…”

“…Owing to its properties it is used, for example, for working machines manufacturing in automobile industry or for manufacturing of aerogenerator components [3,6]. Mechanical properties of cast iron are influenced by the graphite shape, nodularity and distribution [6,7]. A large amount of evenly distributed spheroidal graphite with high nodularity and small diameter has a positive influence on the cast iron properties [2].…”