Study On Sliding And Fatigue Competing Failure Disciplinarian Of NiCr-Cr₃C₂ Coating Deposited By Supersonic Plasma Spraying

As an important form of surface engineering technology, the supersonic plasma spraying（SPS） technology has a wide application prospect in many parts of the surface hardening of rotation and surface repair. However, with different properties of the coating and substrate materials, components with coatings have a different failure mechanism compared with the homogeneous materials. It is of great significance to the further promotion of SPS technology by further studying the failure mechanism of rotating parts reinforced by SPS method.In the present work, the NiCr-Cr₃C₂ coating was fabricated on the 45 steel using SPS technology, the uniform design was used to investigate the relationship between coating properties and spraying parameters, the SEM, TEM, XRD, Hardness test and nano-indention method were used to test the coating morphology, micro-structure, micro-hardness and nano- mechanical properties. In order to investigate the involution of competing life of rolling contact coating, the rolls with coating were tested based on RM-1 rolling contact fatigue platform, and acoustic emission（AE） technology was used to study the relationship between AE parameters and coating failure mechanism, involution of competing life and service stage, results show that:a) Uniform design method was used to investigate the effect of spray parameters, spray current, spray voltage, spray distance and main gas flow rate（Ar gas） on the properties of NiCr-Cr₃C₂ coating. The monitoring for fly speed and temperature of sprayed particle, using spray watch 2i system, verified the correctness of the uniform design result and the optimum spray parameters was acquired.b) The main failure modes of the coating are surface abrasion, spalling and delamination according to the result involution of competing life study based on RM-1 rolling contact fatigue platform under different slip ratio. With the increase of slip ratio, the main failure mode of coating involves to surface abrasion. The P-N curve shows that, with the increase of slip ratio, the average life of coating is about to increasing, while the service life becomes more dispersed.c) The service process is about to divided into 4 stages according to the results of AE parameters, namely normal contact stage, crack initiation stage, crack extension stage and material removal stage. With the service process going on, the AE amplitude is about to increase, during the normal contact stage the AE amplitude is no more than 0.1V, while during the material stage is higher than 5V.d) The main frequency of each stage is not the same according to the results of wavelet analysis. During the normal contact stage, the main frequency ranges from 94 to 188 KHz different from that of material removal stage which ranges from 187 to 374 KHz. Therefore, the changing of frequency can be used to indentify service stage of coating so as to give an early-warning on the failure of coatings.