Evolution of microstructure and wear mechanism in laser clad Al0.5CoCrFeNiSi0.5Tix coatings in response to the Ti addition

Abstract

In this work, the microstructural evolution and its influence on the wear mechanism with the increasing Ti content are investigated in double-layer Al0.5CoCrFeNiSi0.5Tix coatings. The results indicate that FCC solid solution as the matrix phase of first layer changes from cellular structure to columnar dendritic structure due to the addition of Ti. By contrast, BCC solid solution consisting of disordered BCC and ordered B2 are found to be the matrix phase of second layer. Ti promotes the transition of ordered B2 phase from speckle-shape to stripe-shape, and then to square-shape. Besides, Ti facilitates the in-situ synthesis of TiN and TiSi2 in the Ti-containing coatings. Hardness of the coatings is dramatically improved due to the strengthening effect caused by Ti. The acting wear mechanism changes from abrasive wear of coating Ti0 to oxidational wear and mechanical mixing of Ti-containing coatings. The wear weight loss of the coatings decreases drastically with the increasing Ti content, indicating that the microstructural evolution caused by Ti addition has a positive influence on the wear resistance.