Wear behavior of martensitic stainless steel in rolling-sliding contact for planetary roller screw mechanism: Study of the WC/C solution

Abstract

The planetary roller screw mechanism is used in the aeronautics industry for electro-mechanical actuators application. It transforms a rotational movement into a translation movement, and it is designed for heavy loads. The main components are made of martensitic stainless steel, and lubricated with grease. Like most usual rolling mechanisms, smearing and jamming can occur before the theoretical fatigue lifetime, especially in poor lubrication conditions. The actuated load is carried by small contacts between the threads of the screw, the rollers and the nut. The static single contact can be described as an ellipsoid on flat contact with high contact pressure (3-4 GPa). The motion consists of rolling with spin associated with side slip up to 10%. The aim of our study is to investigate the wear behavior of the WC/C coated contact for different operating and design parameters such as load, speed and slip ratio. The contact is simulated by a free rolling roller loaded on a rotating disk. A specific apparatus is used to create a contact with a side slip component, i.e. perpendicular to the rolling direction. The wheel rolling speed and the tangential force generated by the slip ratio are measured. The wear behavior of a WC/C carbon-based composite coating is investigated. It reveals progressive wear and cracking in the rolling direction, i. e. perpendicular to the sliding direction. A wear map has been drawn to establish the damage mode depending on the contact conditions.