Hai-dou Wang

Influence of Surface Roughness on Rolling Contact Fatigue Behavior of Fe-Cr Alloy Coatings

Fe-Cr coating was prepared by plasma-spraying process. As-sprayed coatings were machined by grinding, lapping, or polishing processes as appropriate to get different surface roughnesses. Rolling contact fatigue (RCF) experiments were conducted using a ball-on-disk setup. RCF lifetime of the coating was calculated. The worn morphologies of the coating were observed. Results show that surface roughness obviously influences RCF behavior of the coating. The smooth coatings showed longer RCF lifetimes, and always failed by delamination. The rough coatings always failed by abrasion or spalling. The failure of smooth coatings was driven by the orthogonal shear stress and radial stress, whereas the failure of rough coatings was driven by the asperity contact.

Regression analysis of bonding strength of sprayed coatings based on acoustic emission signal

Abstract The aim of this paper was to obtain the regression equation of the bonding strength of sprayed coatings vs. acoustic emission (AE) signal. FeCrBSi coating, Al2O3-40 wt.% TiO2 (AT40) coating and Al2O3 coating were prepared using an atmospheric plasma spraying system. The microstructures and properties of the coatings were characterized. The coatings exhibited typical laminate structure with low porosity and good bonding interface. The AE signals during indentation testing were abstracted and investigated. AE energy was more sensitive to the coating cracking failure than AE amplitude. Moreover, the energy of AE burst signal had a close positive relationship with coating bonding strength. The distribution characteristic of AE peak energy was discussed based on the Weibull distribution. The best regression equations for the three coatings were obtained to predict the bonding strengths of sprayed coatings based on AE burst signal energy for similar coating/substrate systems.

Effect of indentation conditions on the cracking behavior of a FeCrBSi coating

Abstract A detector combining indentation method and acoustic emission (AE) technique was developed for evaluating the bonding strengths of sprayed coatings. In order to study the effect of indentation conditions on cracking failure behavior of sprayed coating, FeCrBSi coating was prepared by plasma spraying technique. The AE signals during indentation test were abstracted and investigated. The morphologies of indented samples were observed by scanning electronic microscopy (SEM). The results indicate that indentation equipment can induce the cracking failure of coating and AE technique can define the critical statues. The test by interior load was feasible and accurate for evaluating the bonding strength. The key influential factor of indenter lied in the contact area between indenter and coating. The loading rate had little effect on AE signal. The loading conditions were optimized to use diamond indenter with interior load and a loading rate of 100 pulses per second.