Tribological Properties of Electroless Ni-Mo-P/(h)BN Composite Coatings in Wide Temperature Range
Ni-Mo-P coating and Ni-Mo-P/(h)BN composite coating were prepared on the surface of GH4169 nickel-based superalloy by electroless composite plating technique.The tribological behaviour and microstructure of the coatings after friction wear test at different temperatures were investigated.The tribological properties of the coatings at room temperature,300,500 and 700 ℃ were investigated by ball-disc friction and wear test machine.The chemical composition and microstructure of the coatings after friction wear test at different temperatures were analyzed by scanning electron microscope,energy spectrometer and X-ray diffractometer.The mechanical properties of the coatings after friction wear test at different temperatures were characterized by microhardness tester and Rockwell indentation tester.The results show that the deposited Ni-Mo-P coating and Ni-Mo-P/(h)BN composite coating are predominantly amorphous structure containing a small amount of nanocrystalline,and the surface of the coatings is dense.The coatings transform from amorphous to nanocrystalline structure with the increase in the temperature of friction wear test.As the temperature increases,the coatings undergo a transformation from amorphous to nanocrystalline structure,accompanied by an increase in crystallinity.When the temperature increases above 500 ℃,the precipitation of Ni3P hard phase in the coatings occurs,and the oxidative volatilisation of the Mo and P elements results in the formation of pores within the coating and reduction in its density.As the temperature increases,the hardness of the coatings exhibits a fluctuating trend,initially rising and then declining.Concurrently,the adhesion strength between the film and substrate exhibits a gradual decline,progressing from HF1 grade to HF6 grade.With the increase in test temperature,the coefficient of friction and wear rate are both increased first and then decreased,and the highest coefficient of friction is observed at 300 ℃.In the range of room temperature to 500 ℃,the wear and oxidation of the coatings gradually aggravate with the increase in temperature,and the highest wear rate is observed at 500 ℃.Further increasing the temperature makes the friction interface have a better lubrication effect,which improves the friction reduction and wear-resistant performance of the coatings at high temperature.The incorporation of(h)BN particles into the coating enhances the P content,thereby increasing the toughness of the Ni-Mo-P/(h)BN composite coating,improving the hardness of the composite coating,and strengthening the film-substrate bonding.Furthermore,the composite coating exhibits superior wear resistance within the temperature range of room temperature to 700 ℃.
Ni-Mo-P/(h)BN composite coatingmicrostructurehardnessadhesion strength between the film and substratewide temperature range tribological property
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