Abstract: Ni-p electroless plating was adopted to encapsulate the as-received CaF2 in the preparation of precursor mixed powders of NiCr-Cr3C2 -40% CaF23 (wt.%) with an aim to form high-temperature self lubrication wear resistant composite coatings on-TiAl substrate. The microstructure of the coating was examined using XRD, SEM and EDS and the friction and wear behavior of the composite coatings was evaluated using a block-on-ring wear tester at room temperature. The coating has a unique microstructure consisting of primary dendrite TiC and secondary block Al4C3 carbides reinforcement as well as fine isolated spherical CaF2 solid lubricant particles uniformly dispersed in the ductile and tough NiCrAlTi (γ) matrix. The average microhardness of the composite coatings is approximately twice greater than that of the TiAl substrate. The good self lubrication and wear resistant capabilities of the laser clad composite coating were suggested to the Ni-p electroless plating and the attendant reduction of mass loss and the increasing of its compatibility with the NiCrAlTi(γ) metal matrix during the laser cladding.

Key words: microstructure, laser cladding, high-temperature self lubrication composite coating, Ni-p electroless plating, γ-TiAl intermetallic alloy

Author: Liu Xiubo, School of Mechanical and Electrical Engineering, Soochow University, Suzhou 215021, China

E-mail: liubobo0828@yahoo.com.cn

Tribology, Vol. 29, Issue 6, 2009, 499~504