Microstructure and Wear Behavior of Ti-Matrix Functional Gradient Layer

Abstract

To improve the wear-resistance of Ti600, and alleviate thermal stress as well under hyperthermal and excessive temperature difference condition, experiments of Ti-matrix FGM on Ti600 substrate by pulsed Nd:YAG had been carried out. The microstructures, microhardness and phase composition of FGM were investigated. And the friction wear properties of FGM, N-FGM and Ti600 substrate were examined in atmosphere. It was found that a rapidly solidified microstructure consisting of in situ synthesized TiC reinforced phase distributed on FGM substance evenly and dispersely in the form of globular grains had three main different shapes:bulky or imperfect arborescent crystal, fine or approximately equiaxial crystal and chopped fibriform crystal. With the increasing of original Cr3C2content, the number and size of arborescent crystal increased obviously. The distribution of main alloy components was gradient and continuous, presenting the same composition and regularity to the originally preset alloy powder. FGM and N-FGM had an average hardness of approximately 1450, 4.5-5 times of Ti600 substrate, attributed to TiC primary dendrites. With the reducing of weight percentage of TiC, microhardness decreased gradiently and continuously. Meanwhile, the wear resistance of FGM and N-FGM was improved obviously. Friction coefficient, wear loss and wear rate decreased significantly, 0.3-0.5 times of Ti600 substrate.