Phase composition, microstructure evolution and wear behavior of Ni-Mn-Si coatings on copper by laser cladding

Three Ni-Mn-Si coatings were synthesized on copper plate by laser cladding. The compositions of coatings were Ni(40 at.%)-Mn(20 at.%)-Si(40 at.%), Ni(40 at.%)-Mn(30 at.%)-Si(30 at.%) and Ni(40 at.%)-Mn(40 at.%)-Si(20 at.%), respectively. There are Mn5Si2, Mn5Si3, Mn3Si, Ni3Si, Ni2Si, Cu3Si, Mn3Ni2Si and Mn6Ni16Si7 in three coatings. Ni2Si and Ni3Si were found in Coating 1# (Ni40Mn20Si40) and Ni2Si was found in Coating 2# (Ni40Mn30Si30) and there was not any MnSi1.75 − x phase in three coatings. There are not any Ni-Si binary phases in Coating 3# (Ni40Mn40Si20). Mn5Si2 was found in Coating 1# and Mn5Si2 and Mn3Si were found in Coating 2#. Mn5Si2, Mn5Si3 and Mn3Si were found in Coating 3#. There are Mn3Ni2Si phase in Coating 1# and Mn6Ni16Si7 phase in Coating 3#. Mn6Ni16Si7 phases were found in Coating 2#. The highest hardness which is about 1100 HV occurs in the clad layer of Coating 1#. Metal silicides (Ni-Si and Mn-Si phases) are the major factors in increasing the hardness of coatings. There are mainly Ni-Si metal silicides in Coating 1#, Mn-Si metal silicides in Coatings 2# and 3#. Hardness of Ni-Mn-Si coatings depends on Ni-Si phases especially Ni3Si in laser processing. The average friction coefficient for Coating 1#, Coating 2# and Coating 3# is 0.1964, 0.2393 and 0.2582, respectively. Ni-Si phase plays a more important role than Mn-Si in increasing the hardness and decreasing the friction coefficient of coatings.