Effect Of Ti Content On Corrosion Resistance Of Laser Cladding Ni-Based Alloy Coating

Ni-Cr-Mo alloy powder is a kind of laser cladding material with excellent corrosion resistance,In order to improve the corrosion resistance of Laser Cladding Ni-Cr-Mo Alloy Coating in sea water,four different content of Ti(0%?0.3%?30%?6%,wt.%)is added to the Ni-Cr-Mo alloy powder,then the alloy powder was using to fabricate two groups of Ni-Cr-Mo-Ti alloy cladding layer in the argon gas and air.The phase,microstructure,chemical composition,microhardness and corrosion resistance of the cladding layer were measured and analyzed by XRD,SEM,EDS and hardness tester respectively.The Ni-Cr-Mo-Ti alloy cladding layer prepared in argon,the diffraction peaks of the sample of Ti(0%?0.3%?3%,wt.%)move to a larger angle,while the diffraction peak of the sample of Ti(6%)moves to a smaller angle,and NiTi phase was found in the sample of Ti(6%).The grain and grain boundaries in the Ni-Cr-Mo-Ti alloy cladding layer are distinct,and the content of Mo is higher in the grain boundary.The grain size of the sample of Ti(3%)is the smallest,and TiN particles and bright white Mo-rich phase were found in the grain boundary of sample of Ti(6%).The micro Vickers hardness of the Ti(3%)sample is 40-50 HV greater than that of the Ti(0%)sample.In the 3.5%NaCI solution,as the Ti content increases,the corrosion resistance of the Ni-Cr-Mo?Ti alloy cladding layers increases gradually,which may be related to the composition of the passivation film on the surface of the cladding layer,the degree of uniformity of the surface structure and the influence of the grain size,however,the corrosion resistance of the sample of Ti(6%)decreased significantly.The Ni-Cr-Mo-Ti alloy cladding layer prepared in air contains more oxides.The sample of Ti(6%)can not be tested for analysis because of the large number of holes in the surface.In the Ni-Cr-Mo-Ti alloy cladding layer with Ti content of 0%,0.3%and 3%,all of them contained y Ni(Cr,Mo)solid solution.In addition,a small amount of Ti4O7 was found in the cladding layer of 3%Ti content,while the grain was not refined obviously,and the hardness did not increase significantly.Electrochemical test results show that the corrosion resistance of the sample of Ti(3%)is slightly better,but at the end of the passivation phase,abnormal fluctuations was appeared in the polarization curve of the group of Ni-based cladding layer without argon protection,which may be related to TiN and other inclusions.