Demonstration Results

Initial evaluations concluded that S53 has promise as a gear material for applications that do not require a carburized surface. Since it is a stainless steel, S53 becomes austenitic with excess carbon, but there may be other ways to create a hard case. S53 does not need the additional corrosion protection of a sacrificial coating, and has good corrosion performance with a chrome-free adhesion promoter, a chrome-free primer, and topcoat. In the fully hardened state, the mechanical properties of S53 are close to those of 4340M. In rolling/sliding gear testing, S53 shows significantly less damage and causes less distress to counterface materials than does 4340M. Although this testing was limited, it shows that S53 is likely to be a superior material for gears that do not experience high enough Hertzian stresses to require carburization.  From the standpoint of producibility, S53 undergoes higher growth on heat treating than is seen in 4340M and similar steels. Although this growth is isotropic, it will require significant testing to ensure that S53 gears can be designed and fabricated accurately. S53 is more expensive than low carbon ultrahigh strength steels such as 4340M, because of its use of high alloying elements and a more expensive heat treat regimen. However, the material does not require sacrificial coatings for corrosion control.