Laser Surface Processing of Compressor Blades for Erosive Environments

Erosive wear is a significant problem for turbine blades. As part of an Arnold Engineering Development Center program to improve the lifetime of their compressor blades, a laser surfacing process was used to produce a variety of surfaces on blades and blade material. Based on literature reports for coatings, five additives were applied to the surfaces: Cr/CrB2, WC/Co, FeB, Fe2B, and Ni/Cr/CrB2. Dry wear tests, erosive wear tests, metallographic, and compositional analysis and x-ray diffraction analysis were conducted to characterize the materials. The CrB2 and FeB particles transformed to (Fe,Cr)2B and Fe2B as a result of processing. The addition of nickel to the Cr/CrB2 combination produced an fcc iron matrix. All of the surfaces increased the hardness that improved the dry wear by an order of magnitude. The erosive wear however, varied with the additive and the amount of additive. The iron borides actually increased the erosive wear while the CrB2 additions reduced erosion, producing the best result when the matrix was an fcc/bcc iron mixture containing large amounts of an (Fe,Cr)2B phase.