Microstructure And Properties Of Sic Reinforced TiNi Based Composite Coatings On Titanium Alloy Surface By Laser Cladding

Titanium alloys are widely used in defense equipment,aerospace,energy and chemical industries because of their high specific strength,low density,high corrosion and temperature resistance.However,they have the disadvantages of low hardness,poor wear resistance,easy to burn when rubbed in the environment of high temperature and high speed friction.These disadvantages may limit its further application in advanced aero-engines,weapons and equipment.Laser cladding has become a new surface modification technology widely used because of its advantages such as high energy,fast cooling rate,low coating dilution rate,and small heat affected zone.The preparation of metal-ceramic composite coating on the surface of titanium alloy by laser cladding is one of the most important methods to improve the comprehensive mechanical properties of titanium alloy.In this paper,the effects of SiC content and particle size on the microstructure and properties of TiNi-based cladding coating were studied.The rule of effect of SiC content and particle size on the microstructure of TiNi-based cladding coating was obtained.That is,the reinforcement phase appeared in the cladding coating was the main reason for the improvements of hardness and wear resistance,the unmelted particles will contribute to the improvement of the wear resistance.Based on this rule,B₄C particles were added to further enhance the microstructure and properties of the cladding coating.The effect of B₄C content on the microstructure and properties of Ti/Ni/M-SiC cladding coating was studied.The study will provides a theoretical basis for the experiment of microstructure and properties of SiC reinforced TiNi matrix composite coatings on Titanium alloy surface by laser clading.The experimental results of the effect of SiC content on the microstructure and properties of TiNi-based cladding coating show that:after micron SiC is added,SiC is not completely decomposed,the main phase of the cladding coating is Ti₂Ni,TiNi,Ti₅Si₃,TiC and SiC;with the increase of SiC content,The content of TiNi/Ti₅Si₃ eutectic structure and TiC in the cladding coating increased,and the content of Ti₂Ni decreased.The hardness of the cladding coating increased first and then decreased.When the content of SiC reached 8 wt.%,the hardness of cladding coating was 2.5 times higher than that of the matrix.The wear resistance of cladding coating shows an increasing trend,which is the best and is 2.1 times that of the matrix when the content of SiC is 10 wt.%.The strengthening phase in the cladding layer is the main reason for the increase in hardness and wear resistance,and the unmelted particles contribute to the improvement of the wear resistance.The experimental results of the effect of SiC particle size on the microstructure and properties of TiNi-based cladding coating show that the main phases in the two cladding coatings are same,and the nano-SiC is completely decomposed;the TiC particles play the role of grain refinement;the micro-SiC cladding coating The hardness and wear resistance of coating increased 2.1 times and 2.082 times respectively.The hardness and wear resistance of the nano-SiC cladding coating increased to 2.4 times and 1.475 times respectively.Micro-SiC particles helped to increase the wear resistance of cladding coatings,nano-SiC particles help to increase the hardness of the cladding coatings.The experimental results of the influence of B₄C content on the microstructure and properties of Ti/Ni/Micro-SiC cladding coating show that:after the introduction of B₄C in Ti/Ni/Micro-SiC powder,the B₄C particles are not completely decomposed;the newly added phase of the cladding coating is TiB₂,TiB₂ and TiC forms a TiB₂-TiC composite structure.When the content of B₄C is 10 wt.%,the hardness and wear resistance of the cladding coating are the best,the hardness of cladding coating is 3.1 times and 3.621 times than that of the matrix,the wear resistance of cladding coating is 1 time and 1.740 times than that of the Micro-SiC cladding coating.