Preparation And Properties Of Reactive Plasma Sprayed TiC/Co-Ni Alloy Composite Coatings

In this paper,graphite powder and titanium powder were used as raw materials to prepare Ti-C composite powder suitable for spraying by spray granulation technology,and the composite powder was added to Co-Ni alloy powder to utilize self-propagation between Ti and C.The reaction forms TiC to prepare a TiC/Co-Ni alloy composite coating that satisfies wear resistance under high temperature conditions.The effects of the amount of Ti-C composite powder on the microstructure and properties(hardness,normal temperature friction and wear,thermal shock resistance,high temperature oxidation,high temperature friction and wear)of the composite coating were investigated.After adding Ti-C composite powder to the cobalt-based alloy powder,the formation of TiC phase was detected in the composite coating phase obtained by reactive plasma spraying,and also contained the main phase Co in the alloy powder,the secondary phase Fe₃Ni₃B and Ni₃₁Si₁₂.The Ti-C composite powder was added to the cobalt-nickel alloy powder,and the main phase of the composite coating was TiC and Ni-Cr-Co-Mo,and the secondary phases were Ti O and Ti2O,It indicates that a small amount of Ti powder is oxidized during the spraying process.As the amount of Ti-C composite powder increases,the porosity of the composite coating increases,and the microhardness increases first and then decreases.When the addition amount is 15%Wt,the microhardness of the composite coating is the highest,the cobalt-based alloy composite coating is 1035.3 HV_0.2,and the cobalt-nickel alloy composite coating is 854 HV_0.2.The wear resistance of the composite coating is significantly improved at room temperature.By analyzing the wear scar morphology of the coating,it is found that the wear mechanism of the coating is mainly abrasive wear and adhesive wear.The thermal shock test results show that the thermal shock resistance of the composite coating under 900? water quenching and thermal shock is better than that of a single alloy coating.The thermal shock resistance of the 15wt.%TiC/Co-Ni alloy composite coating is Optimal,the number of thermal shocks is 47.The high temperature oxidation resistance and high temperature wear behavior of Co-Ni alloy coating and 15%Wt TiC/Co-Ni alloy composite coating were studied.The test results show that:The coating has the formation of oxides Cr₂O₃ and Co Cr₂O₄(Ni Cr₂O₄)in the coating after high temperature oxygen,and the formation of Ti O₂ in the composite coating.Through the study of the oxidation kinetics curve of the coating,it is found that the oxidation of the coating changes dynamically with time and temperature.At high temperature wear at 600? to 800?,the high temperature friction coefficient of the coating tends to decrease with increasing temperature due to the certain lubricating effect of the oxide film.The high temperature wear performance of the composite coating at 800? is better than that of the alloy coating.The wear mechanism of the coating under high temperature conditions is changed from abrasive wear and adhesive wear to oxidative wear.