Elevated temperature evaluation of fretting and metal transfer between coated titanium components

During fretting, small amplitude displacements and high normal surface load s combined with abrasive oxide particles cause surface damage that acts as initiation sites for fatigue cracks. Since these conditions are prevalent w ithin the titanium dovetail joints of jet engines a wear mode analysis was performed on extended service jet engine disks and compressor blades. The r esults of the wear mode analysis indicated that titanium from the uncoated disk was transferred to the softer copper-nickel-indium coated dovetail sur face of the blades. This transfer created titanium on titanium contact and eventually fretting weal: In order to simulate these conditions, a moderate displacement (125 mu m), low cycle phase followed by a small displacement (25 mu m), high cycle fretting phase utilizing a cylinder on flat configura tion was developed. The analysis and test procedure developed during this,s tudy will ultimately aid in the selection and evaluation of a new coating c apable of preventing fretting.