Effect Of Post-treatment On Rolling/sliding Competing Failure Of NiCrBSi-30%Mo Coating Deposited By Plasma Spraying

Wear and contact fatigue are common failure modes of rolling parts.Thermal spraying technology,as a common surface enforcing technology,is usually used for surface protection and restoration of parts.However,some factors,such as micro-defects inevitable in coating,low bonding strength between coating and substrate,extremely influenced its friction and wear properties and contact fatigue performance.Heat-treatment,such as remelting and hot isostatic processing(HIP)can improve the quality of coatings.Therefore,it is of great significance to further explore the effect of post-treatment on the structure and tribology performance of thermal sprayed coatings.In this paper,the research was carried out to study the influence of post-treatment on sliding and fatigue competing failure disciplinarian of NiCrBSi-30%Mo coating deposited by plasma spraying.The SEM,TEM,XRD and EDS were used to test the coating microstructure,the formation mechanism of micro-defects such as micro-pores and micro-cracks were explored.The flame remelting and HIP technologies were used to modify the as-sprayed coating.The friction and wear test of coatings before and after treatment was carried by a sliding wear apparatus.The rolls with coatings were tested based on rolling contact fatigue tester to explore the failure mode and mechanism.The results showed that:(1)The structure and mechanical properties of the post-treated coatings were better than the as-sprayed coating.The micro-hardness of flame remelted coating surpassed that of HIPed coating and was by far superior to the as-sprayed coating.The elastic modulus of HIPed coating surpassed that of the flame remelted coating and was by far superior to the as-sprayed coating.The changes of mechanical properties were associated with the multiphase structure and micro-defects.(2)Under the condition of dry friction and wear,the main wear mechanism of the as-sprayed coating was adhesive/delaminative wear,the main wear mechanism of the flame remelted coating was adhesive wear,and the main wear mechanism of the HIPed coating was abrasive/adhesive wear.The wear volume of the three coatings was less than the substrate.The wear resistance could be modified by depositing coatings on the surface.(3)Under the condition of boundary lubrication,the friction coefficient of as-sprayed coating exceeded the substrate under the condition of large load,which can be attributed to the increase of surface roughness and decrease of lubrication viscosity.The main wear mechanism of the as-sprayed coating was abrasive/delaminative wear,the main wear mechanism of the flame remelted coating was abrasive wear,and the main wear mechanism of the HIPed coating was delaminative wear.(4)The main failure modes of the coatings are pitting,spalling and delamination.The internal structure and extra force worked together to influence the failure modes.(5)Under the same experimental condition,the value of the fatigue life of the flame remelted coating was the best,the as-sprayed coating was the worst,and the HIPed coating was mediate.The order of dispersion was contrary to the value of the fatigue life.The P-N curve showed that,compared with the rolling contact condition of 0% slip ratio,the value of fatigue life decreased while the dispersion increased under the condition of 50% slip ratio.