• Tribology and Lubricants
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• v.13 no.1
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• pp.42-52
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• 1997

This paper deals with wear characteristics of ion-nitrided metal theoretically and experimentally in order to analysis of wear phenomena. Wear tests show that compound layer of ion-nitrided metal reduces wear rate when the applied wear load is mall. However, as th load becomes large, the existence of compound layer tends to increase wear rate. The residual stress at the surface of ion-nitrided metal is measured, and the internal stress distribution is calculated when the normal and tangential forces are applied to the surface of metal. Compressive residual stress is largeest at the compound layer, and decreases as the depth from the surface increases. Calculation shows that the maximum stress exists at a certain depth from the surface when normal and tangential force are applied, and that the larger the wear load is the deeper the location of maximum stress becomes. In the analysis, it is found that under small applied wear load the critical depth, where voids and cracks may be created and propagated, is located at the compound layer, as the adhesive wear, where hardness is an important factor, is created the existence of compound layer reduces the amount of wear. When the load becomes large the critical depth is located below the compound layer, and delamination, which may be explained by surface deformation, crack nucleation and propagation, is created, and the existence of compound layer increases wear rate.

• Journal of Welding and Joining
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• v.18 no.5
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• pp.105-111
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• 2000

The wear behavior of thermal sprayed AlSiMg-40TiC composite coatings were studied as a function of load and sliding velocity under unlubricated conditions. Experiments were performed using a block-on-ring(WC-6wt%/Co, Hv 1500) type. The tests were carried out a various load(30∼ 125.5N) and sliding velocity(0.5∼2.0m/s). Three wear rate regions were observed in the AlSiMg-40TiC composite coatings. The wear rate in region I at low load (less then 8N( were less than 1×{TEX}$10^{-5}${/TEX}㎣/m. Low wear rates in region I resulted from the load-bearing capacity of TiC particles. The transition from region I to II occurred when the applied load exceeded the fracture and pull-out strength of the particles. The TiC fractured particles trapped between the specimen and the counterface acted as third-body abrasive wear. The subsurface layer worn surface in region II was composed of the mechanically mixed layer (MML). The wear rate increase abruptly above a critical load (region III). The high wear rate in region III was induced by frictional temperature and involves massive surface damage.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.2
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• pp.193-197
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• 2002

The frequency dependency of the Rayleigh surface wave was investigated indirectly by measuring the angular dependency of the backward radiation of the incident ultrasonic wave in the abrasion specimens, which was explained in view of the residual stress distribution. The peak intensity of the backward radiation profile decreased and the right half width of the profile increased with an increase of the variational rate of residual stress for the scuffing specimen. The peak intensity was also affected by the surface wave scattering during the propagation around the micro-damages. The peak angle might depend on not only the amount of residual stress but also the micro-structure. The result observed in this study demonstrates the high potential of the backward radiated ultrasound as a tool for the nondestructive evaluation of the subsurface gradients of materials.