Microstructure Evolution And Performance Evaluation Of Nano Composite Coating For Key Friction Pairs Of Airport Power Machinery

With the expansion of the passenger and cargo throughput of civil airports,the power demand and load of all kinds of power machinery are rapidly increasing.Under the inevitable trend of high-strength development of power machinery,the valve seat area of the engine needs better performance conditions.With its own unique advantages,laser cladding technology can not only achieve large-area surface repair,but also complete local area accurate surface modification.Therefore,this paper chooses vermicular graphite cast iron as the matrix material,and uses laser cladding technology to prepare composite alloy cladding layers with different laser process parameters and different cladding material ratios to improve the surface strength and performance of vermicular iron materials.Use SEM,EDS and other technical means to explore the effects of laser power,scanning speed,nano-lanthanum oxide addition and titanium powder mass ratio on the crystal grain structure and mechanics of laser coatings through tissue observation,hardness measurement,electrochemical testing,and friction and wear experiments.The role of performance to reveal the law and mechanism of changes in the performance of laser coatings on the surface of vermicular iron.This paper first designed a total of 6 sets of process parameters with different powers and scanning speeds,and observed and tested various performances of the coatings obtained in the experiment.The results showed that: appropriately reducing the power and increasing the scanning speed can significantly refine the structure grains.This has a certain positive effect on the improvement of hardness,wear resistance and corrosion resistance.The cladding layer with changing the content of nano-lanthanum oxide was studied,and the optimal addition amount of nano-La2O3 was determined to be 2%.The effect of rare-earth oxide addition on the refined structure is 2%>1%>3%>0%.This is the same as the law of influence on the hardness,corrosion resistance and wear resistance of the coating;adding nanolanthanum oxide in the range of 0～2% can increase the Cr,Ni,Si and other elements in the cladding layer and accelerate the diffusion effect of the middle element which is the molten pool;when the addition amount of nano-La2O3 is 2%,the effect of suppressing cracks is the best.When the rare earth oxide content is 0%,1%,2%,the wear type of the cladding layer is abrasive wear + oxidation wear,and when the addition amount is 3%,it is abrasive wear.Finally,this article studies the changes in the cladding material ratio to 1.5% and 2.5%titanium coatings.The results show that titanium powder can play a role in refining the structure,and this effect is positively correlated with the Ti powder content.;The more the mass ratio of titanium powder,the more refined the grains of the coating structure,the better the uniformity of the structure,the increased hardness of the cladding layer,and the better corrosion resistance and wear resistance;Adding can increase the content of Fe and C in the cladding layer,while the content of Mo and Co in the cladding layer also increases slightly;Ti powder has a certain inhibitory effect on the CO pores generated in the cladding layer.As it increases,the porosity decreases.