Technological tests regarding the qualification of the REACh compliant surface treatment processes for helicopter dynamic systems

Abstract

REACh regulation imposes to European industrial companies to apply viable alternatives for the components which contain hexavalent chromium from 2017. Hexavalent chromium is mainly used in surface treatment operations, which affect the strength relevant properties of the helicopter components, such as the fatigue behaviour as well as the resistance against wear, fretting and corrosion. The components of the helicopter's dynamic system treated by alternative surface treatment processes have to be certified after the qualificationof the REACh compliant processes. This paper presents a technological test program used for determining the performances of the proposed REACh compliant surface treatment processes compared to the current ones. One key issue for the dynamic system components is the contact between two components for which new surface treatments will be applied. In order to determine the contact pairs to be tested, a complete screening of the critical components of the dynamic system has been performed, whose failure is catastrophic (e.g. rotors, gearboxes, etc.), and representative technological samples have been designed. This technological test program includes the fretting wear tests for different plane to plane contacts, fretting fatigue tests in cylinder to cylinder contacts, corrosion tests inside bolted connections and the combined wear-corrosion tests. The principle is to compare each time the current design with the REACh substitutes. Depending on these tests results, some complement can be done in case of differences observed or some additional specific tests can be required based on the service experience coming from the development and/or major incidents. The results of the technological test provide not only a performance check required for the certification of the REACh compliant products, but also an extensive experimental knowledge on the fatigue, wear, corrosion and fretting resistance of the materials used in the aerospace industry.