What is a common feature of case-hardened steel used for piston pins?

Case-hardened steel is specifically designed to enhance its surface hardness while maintaining a tough, ductile interior. This process involves hardening the outer layer of the steel, which significantly increases its wear resistance. In applications such as piston pins in engines, where components are subject to high levels of friction and stress, the durability provided by high wear resistance is crucial.

This property minimizes the wear and tear that can occur between the piston pins and other engine components, promoting longevity and better performance. High wear resistance means that the material can withstand the abrasive conditions it experiences without degrading quickly, which is essential for maintaining engine efficiency and reliability over time.

The other options do not align with the characteristics of case-hardened steel. For instance, it is actually heavier than aluminum, does not typically allow for faster thermal expansion, and is not designed to be more susceptible to corrosion; in fact, many case-hardened steels are treated to be more resistant to corrosion.