| Friction wear and fatigue wear are the common failure modes of rotating machinery parts.The thermal spraying NiCr-Cr3C2cermet coatings have been widely for many fields because of their excellent wear resistance and contact fatigue resistance.While,the contact fatigue resistance of coating will be greatly reduced,leading to coating failure occur during service process,due to the porous,multi-interface structure problem,which easily cause the hard phase flake and micro crack initiation.Therefore,for further promotion of NiCr-Cr3C2cermet coatings on rotating machinery parts,it is of great significance to optimize the preparation technology for extending the service period of components,do deep analysis fatigue life and mechanism of coatings.In this paper,NiCr-Cr3C2cermet coatings were deposited by supersonic plasma spraying technology（SPS）and high velocity oxy-fuel technology（HVOF）.The microstructures,mechanical property,wear properties of coatings were analyzed and compared by different equipments and methods for identifying the most suitable process for the preparation of NiCr-Cr3C2cermet coatings.In order to investigate the failure modes and mechanism of coatings,the contact fatigue experiment was tested based on RM-1rolling/sliding contact fatigue machine.The hot isostatic pressing technology was used to deal with the coating.The structure,property,the fatigue life were analyzed.Finally the results showed that:（1）The microstructures,mechanical property of SPS coating are superior to those of HVOF coating.Whether under the condition of dry sliding friction or fretting oil lubrication,the fluctuation,the friction coefficient values,the wear volume loss of the SPS coating are lower than those of HVOF coating.Thus,the wear property of SPS coating isbetter than HVOF coating.（2）In the dry sliding friction condition,the main wear mechanism of both coatings is‘third body’abrasive wear caused by the cracking or spalling of carbide particles and lamellar cracking resulted from cracks induced by stress concentration.The fretting friction of both coatings is the combination of abrasive wear and fatigue delamination wear.（3）The failure modes are divided into three categories:surface abrasion,spalling,delamination according to the research on involution of coating life under different contact stress.When the contact stress was low,the probabilities of abrasion and spalling type failures near surface were high.Under the high contact stress,the coating was prone to be failed with delamination.（4）Based on the contact fatigue test data under three contact stress,the P-N curve was established.It can be seen that from this curve,under the high contact stress（1.0GPa）,the scattering degree of the fatigue life was high andβwas 2.4887.Under the low contact stress（0.5GPa）,the scattering degree of the fatigue life was low andβwas 6.5334.（5）After hot isostatic pressing,the comprehensive performance of the coating was improved,such as,the coating porosity was decreased from 1.89%to 1.38%and the bonding strength was increased from 68MPa to 71MPa.Under the same contact stress,the contact fatigue life was evidently enhanced after treatment than that of untreated.Under0.5GPa,the cyclic time was increased from 1.588×105 to 2.267×105.The main failure mode of coating was surface abrasion and spalling after hot isostatic pressing. |
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