Alloys Design And Performance Study Of CuAl-based Abradable Sealing Coating Based On First-principles

Copper-aluminum alloy has good strength,hardness and self-lubrication.It’s often used as a raw material for soft wear-resistant coating materials and copper-based abradable sealing coatings.The Al content has a significant effect on the phase composition of the copper-aluminum alloy,which in turn affects the properties of the alloy and the coatings.In this paper,Cu Al alloys with Al content ranging from 0 to 10 wt.% were researched.The influence of Al content on the alloy and coating properties was systematically studied.This work was modeled using a special quasi-random structure(SQS).The properties such as lattice constants,mechanical properties,hightemperature mechanical properties,thermal expansion coefficient,specific heat capacity,melting point,oxidation resistance properties,and phase stability were calculated using first-principles calculations.Meanwhile,Cu Al alloys for Al contents of 5wt.%,7wt.% and 9wt.% were prepared by vacuum melting.The properties such as phase composition,microstructure,room/high temperature mechanical properties,thermal properties and chemical stability were characterized.The experimental results were compared with the results of first-principles calculations.The influence of Al content on the alloy properties were explored.The optimal Al content range for the skeleton phase applied to the abradable sealing coatings were determined.Cu7Al/PHB coatings were prepared by atmospheric plasma spraying.The microstructure,mechanical properties,thermal properties and chemical stability of Cu7Al/PHB coatings were studied.Static oxidation experiments at 500°C and 600°C for Cu7Al/PHB with 1000 h were carried out.The change of coating properties under long time high-temperature environment was investigated.The main findings of this paper are as follows:The calculation results showed that the increase of Al content in Cu Al alloys increased lattice distortion and the lattice constant of Cu Al alloys.As the Al content increased,the theoretical Young’s modulus of the alloy tends to rise and then fall.This trend is caused by the fact that the Young’s modulus of the β` phase is greater than that of the α phase.The increased of temperature causes a significant decrease in Young’s modulus,which decreased by about 22% changing from the base state(T=0K)to 870 K.With the increased of Al content,the melting point tended to decrease.The thermal expansion coefficient of the alloy tended to rise with the increased of Al content.The specific heat capacity first rose and then fell.The binding energy and oxygen impurity formation energy of the alloy tended to decrease with the increase of Al content.The bonding energy and oxygen impurity formation energy of the alloy tended to decrease with the increase of Al content,indicating that the phase stability and oxidation resistance both tend to increase.The experimental analysis of the alloy showed that only α-phase existed in the5 wt.% and 7wt.% Al content Cu Al alloys,but both α-phase and β’ phase existed in the9 wt.% Al content Cu Al alloy.The lattice constant and hardness of Cu Al alloy tended to increase with the increased of Al content.The Young’s modulus of the alloy decreased and then increased as the Al content increased.The calculated Young’s modulus was in good agreement with the experimental results.The melting point showed a decreasing trend.It also was in good agreement with the calculated value with an error of no more than 1.4%.With the increase of Al content,the oxidation resistance of the alloy showed an increasing trend.Taking into account multiple properties of the alloy,the Cu Al alloy with 7wt.% Al content was preferred for preparation and performance testing.Based on the results of calculations and alloy properties tests,Cu7Al/PHB abradable sealing coatings were prepared by atmospheric plasma spraying.The room temperature Vickers hardness of the coating Hv0.1 is approximately 120.8.The effect of temperature on the Vickers hardness of the coating is more significant.With the increased of temperature,the oxidation weight gain rate of the coating accelerated.The oxidation resistance of the coating was good below 620°C.Static oxidation experiments were conducted at two sets of temperatures,500°C and 600°C with 1000 h.The results showed that the oxidation temperature has a significant effect on the coating composition relative to the oxidation time.The coating hardness tended to increase with the oxidation time.The corrosion tests showed that the coating had good corrosion resistance.The Cu7Al/PHB optimized by this work is superior to the existing commercial Cu9Al/PHB coatings in terms of mechanical properties and stability.