Study On Impression Creep Properties Of Babbit Alloys

Babbitt alloy is an excellent material for manufacturing sliding bearings and bushings with excellent wear resistance and embedability.In addition to friction and wear,sliding bearing and bearing bush are subject to temperature and stress.Hence,sliding bearing and bearing bush are prone to creep,which lead the matching relation between the shaft and the sliding bearing or bearing bush not guaranteed.These are easy to cause a series of problems such as the jumpiness of the shaft.In this paper,the impression creep behavior of lead-based Babbitt alloy PbSn16Sb16Cu2and tin-based Babbitt SnSb8Cu4,SnSb8Cu8 were studied using the self-made creep test equipment under constant punch stress in the range of 15–30 MPa and at temperatures in the range of 333–393 K.The constitutive equation was constructed and the mechanism of creep deformation was explored.The microstructure evolution of Babbitt alloy was analyzed by XRD,SEM and EDS.The research results are as follows:?1?The stress exponents n of lead-based Babbitt PbSn16Sb16Cu2 is 4.12,and activation energy values Q is 60.56 kJ/mol under experimental conditions.The material structure constant A is 1.47×10⁷ and the impression creep constitutive equation of the steady state of creep is as follows:???The stress exponents and activation energy values are indicative of a dislocation climbing controlled dominated by grain boundary diffusion creep mechanism.?2?Under the creep experimental conditions of the tin-based Babbitt SnSb8Cu4 and SnSb8Cu8,the constitutive equation is constructed according to the stress exponents n,the activation energy values Q and the material structure constant A.a)The stress exponent n of Babbitt SnSb8Cu4 is 2.42,and the activation energy values Q is 39.85 kJ/mol.The material structure constant A is 19.702,and the impression creep constitutive equation of the steady state of creep is as follows:???The stress exponent and activation energy values are indicative of a dislocation sliding controlled dominated by grain boundary diffusion creep mechanism.b)The stress exponent n of Babbitt SnSb8Cu4 is 3.36,and the activation energy values Q is 51.90 kJ/mol.The material structure constant A is 4.9×10³,and the impression creep constitutive equation of the steady state of creep is as follows:???The stress exponents and activation energy values are indicative of a dislocation sliding controlled dominated by lattice diffusion and dislocation pipe diffusion creep mechanism.?3?The matrix of lead-based Babbitt alloy PbSn16Sb16Cu2 is mainly composed of Pb and lamellar uniformly distributed Sn eutectic structure.The square phase SnSb and the short rod phase Cu₆Sn₅ were dispersively distributed in the matrix.With the increasing of temperature and stress,the matrix was softened,and the SnSb phase strength was decreased after creep.As a result,the alloy can not resist creep deformation and its creep resistance decreased.?4?The tin-based Babbitt alloy SnSb8Cu4 mainly consisted of?-Sn matrix and reinforcing phase Cu₆Sn₅.The Cu₆Sn₅ phase had high thermal stability and strong resistance to creep deformation at low temperature and stress during creep process.With the increasing of temperature and stress,the microstructure coursed and Cu₆Sn₅ phase was broken,resulting in a plasticity decrease of alloy.Due to the relatively high strength of the Babbitt SnSb8Cu4matrix and the high content of Cu₆Sn₅ phase in the microstructure,the impression creep resistance was better than that of the lead-based Babbitt alloy PbSn16Sb16Cu2.?5?The tin-based Babbitt SnSb8Cu8 consisted of?-Sn matrix,SnSb phase and Cu₆Sn₅phase.Compared with SnSb8Cu4,Babbitt SnSb8Cu8 had more content of Cu₆Sn₅ phase and SnSb phase,thus the alloy had higher strength and better creep resistance at lower temperature and stress.SnSb phase grew and coarsened under higher temperature and stress,which separated the matrix.When the temperature was higher than 373 K,the SnSb phase has poor thermal stability and the creep resistance,therefore the creep resistance was worse than that of the Babbitt SnSb8Cu4.