The Effect Of Ferroalloy Types On The Structure Evolution And Properties Of Laser Powder Deposited Copper-based Alloys

Copper and copper alloys with excellent electrical,thermal conductivity,and corrosion resistance are widely used in industry.Even through work hardening,the strength and hardness of copper are still far below the use requirements.Generally,the Fe-based alloys not only have high hardness and wear resistance,but also have low cost.Especially,Fe-based amorphous alloys have high corrosion resistance.In this paper,according to the liquid immiscibility of Cu-Fe alloy,many Fe-rich particles were prepared in situ to enhance Cu-based alloys by laser powder deposition.The effects of ferroalloy types on microstructure,liquid phase separation characteristic,size distribution and internal structural evolution of Fe-rich particles,hardness,wear resistance,and corrosion resistance of Cu-Fe immiscible composites were studied.The obtained main results are as follows:Firstly,the Cu88Fe12 immiscible coating（the composition of ferroalloy is Fe-12Ni-5Cr-0.6Si-0.2C（wt.%））was prepared by the laser powder deposition.The microstructure of the coating is mainly composed of large amounts sphericalγ/α-Fe particles dispersed in the Cu-rich matrix.Due to the presence of Fe-rich particles,the hardness of the immiscible coating is improved significantly.In addition,due to the“shadow protection effect”of Fe-rich particles on the Cu-rich matrix,the degree of deformation and ploughing on the worn surface of Cu-Fe immiscible coating is far less than those of brass.Therefore,the wear resistance of Cu-Fe immiscible coating is obviously improved compared with that of brass.Based on the previous experiments,the hardness and wear resistance of Cu-Fe immiscible coating can be further improved by increasing the Fe content.The ferroalloy powder was replaced with 12Cr1Mo1V.Similarly,the Cu80Fe20 immiscible coatings are prepared by laser powder deposition.The results showed that,as the laser scanning speed increases from 8 mm/s and 10 mm/s to 12 mm/s,the particle size of Fe-rich particles decrease from 7.54±0.302μm and 6.44±0.258μm to 5.32±0.213μm,respectively.The decrease of the Fe-rich particles size and the distance between adjacent particles enhance the“shadow protection effect”of Fe-rich particles on Cu-rich matrix.Therefore,with the increase of scanning speed,the hardness and wear resistance of Cu-Fe immiscible coating gradually improve,which are higher than those of brass.Due to the excellent properties of amorphous alloy,such as high wear resistance and corrosion resistance,the Fe-based amorphous alloy（Fe-W-Mo-Cr-Ni-Si-B-Mn-C（wt.%））is introduced into Cu-based alloy.The Fe-based amorphous alloy reinforced Cu-based immiscible composites are prepared by laser powder deposition.The macroscopic morphology of composites shows that,with the increase of energy density,the bonding quality between adjacent tracks experiences a transition from“poor bonding（crack）”to“good bonding”and“crack debonding”.Moreover,due to the occurrence of liquid phase separation,the Fe-rich particles are dispersed in Cu-rich matrix.The internal microstructure of Fe-rich particles is that fishbone eutectic skeleton M₂₃C₆,spur-like Cr Fe₇C_0.45,and white carbide M₁₂C are distributed in the Fe-rich particles.Therefore,the corrosion resistance of composites is the worst because of the low energy density caused by the gap between adjacent tracks.With the increase of the energy density,the oxidation film on the Fe-rich particles surface can protect on the Cu-rich matrix.However,with the further increase of the energy density,the crack initiation of Fe-rich particles will reduce the protective effect of the oxide film on the Cu-rich matrix.