Laser cladding for high-temperature self-lubricating wear-resistant composite coatings on γ-TiAl intermetallic alloy Ti-48Al-2Cr-2Nb

ABSTRACT High-temperature self-lubricating wear-resistant metal matrix composite coatings are fabricated on substrate of a -TiAI internietallic alloy Ti-48A1-2Cr-2Nb by laser cladding. The hybrid ' -NiCr metal matrix composite coating is mainlyreinforced by rapidly solidified wear-resistant phase ofhyper-eutectic MC3 and self-lubricating particles ofAg and CaF2 orCaAgF4. Mi.crostructure and hardness within the whole laser clad composite coating is homogeneous and the bonding to thesubstrate is purely metallurgical. Both hardness and dry sliding wear resistance of the i -TiAI intermetailic alloy aresignificantly enhanced after laser cladding treatment. Keywords: Y -TiAl intermetallic alloy, High-temperature wear-resistant composite coatings, Laser cladding, Self lubrication 1. INTRODUCTION y -TiAl intermetallic alloys have great potentials for elevated-temperature applications in the aerospace and automotiveindustries because of their high specific strength, high specific modulus and good creep resistance. Significant progresshas been made in the past decade on improving the room-temperature ductility and high-temperature (>85OC) oxidationresistance by alloy modifications, processing innovation and surface engineering.46 Attentions are also attracted to theimprovement on wear resistance of TiA1 intermetallic alloys because it is one of the key properties when applied astribological components.7'2 Wang et al7 utilized multi-arc ion plating (MIP) method to deposite TiN thin films on surface ofTi-SOA1-2Mn-1.5Nb. Noda et a1 employed plasma carburization to fabricate a Ti2A1C hard thin film in a thickness of 3mon a cast fully lamellar Ti-33.5Al-lNb-O.5Cr-O.5Si alloy. Laser surface alloying was also employed9to enhance the wear