Microstructure and wear properties of Ni-based composite layer on aluminum alloy by laser cladding

Abstract:

The microstructure and wear properties of Ni-based composite coatings on aluminum alloy by laser cladding were investigated by means of SEM, EDS, a microhardness tester and friction tester. The results showed that the holes and cracks are relatively few in the layer when the scanning speeds of 5 mm/s.Many massive and continuous network Ni-Al intermetallic compounds formed at top of the cladding layer, and (Ni, Cr, Fe) XCy intermetallic compounds were formed at the middle of the cladding layer. The microstructure of the bottom cladding layer consisted of the columnar α-Al dendrite with obvious growth direction. The middle and the top of the cladding layer maintained a high microhardness value. The microhardness of the middle of layer had a maximum value of 820HV, which was more than 5 times that of the bottom of the cladding layer. The microhardness decreased sharply at the end of the middle of layer. The friction coefficients of the layer have a fluctuation with the different of load, and it decreased with the load increasing. The Ni-Al and (Ni, Cr, Fe) XCy intermetallic, forming and distributing on the top and middle of the cladding layer were the primary reason for the improvement of the microhardness and wear of the layer.

Key words:Laser cladding; Aluminum alloy; Ni-base composite; Ni-Al intermetallic compounds; (Ni, Cr, Fe) XCy intermetallic compounds