Abstract: Ceramic coatings are often used in applications requiring high hardness, wear resistance, and corrosion protection, such as fluid rotary joints (FRJ) in aerospace applications. In this investigation, excessive leakage on a FRJ was attributed to porosity, microcracks, and surface roughness of thermal sprayed chromium oxide (Cr2O3) ceramic coating, which nominally provides a sealing surface on a stainless steel shaft that mates with polytetrafluoroethylene (PTFE) seals. The FRJ is part of a 360-degree rotational assembly. Several materials were tested and evaluated for leakage, wear, and torque: chromium oxide, thin dense chrome, 17-4 PH stainless steel and tungsten carbide (10% Cobalt – 4% Chromium). Test results supported a change to tungsten carbide (10% Cobalt – 4% Chromium), owing to successful life qualification of the assembly and acceptable leakage, wear, and torque values.
Authors: Kevin Chasse, John Dahill, Aaron West, Daniel Zivi, and Michael Bednarczyk
Keywords: Failure Analysis, Chromium Oxide, Thermal Spray, Fluid Rotary Joint, Seals, Wear