This study presents a comparative analysis of the water droplet erosion resistance of three compressor wheels coated with Ni-P and Si-P layers. The tests were conducted using a custom-developed experimental apparatus in accordance with the ASTM G73-10 standard. The degree of erosion was monitored through continuous precision mass measurements, and structural changes on the surfaces of both the base materials and the coatings were examined using a Zeiss Crossbeam 350 scanning electron microscope (SEM). Hardness values were determined using a Vickers KB 30 hardness tester, while the chemical composition was analysed using a WAS Foundry Master optical emission spectrometer. Significant differences in erosion resistance were observed among the various compressor wheels, which can be attributed to differences in coating hardness values, as well as to the detachment of the Ni-P layer from the base material under continuous erosion. In all cases, water droplet erosion led to a reduction in the isentropic efficiency of the compressor—measured using a hot gas turbocharger testbench—with the extent of efficiency loss depending upon the type of coating applied. Although blade protection technologies for turbocharger compressor impellers used in the automotive industry have been the subject of only a limited number of studies, modern technologies, such as the application of certain alternative fuels and exhaust gas recirculation, have increased water droplet formation, thereby accelerating the erosion rate of the impeller. The aim of this study is to evaluate the resistance of three different coating layers to water droplet erosion through standardized tests conducted using a custom-designed experimental apparatus.

Wear is the third most important factor that restricts the longevity of total knee replacements (TKRs). Wear is particularly influenced by load, local kinematics between the contact surfaces and presumably by the geometry of the contact surfaces. This article investigated, by means of multibody models, how wear in total knee replacements is affected by the size of a TKR or by TKR-related geometric parameters during gait motion. As a result, it has been established that wear rate increases linearly as a function of TKR size, while the impact of TKR-related geometric parameters can be described by linear or quadratic functions. One can conclude that the newly introduced dimensionless parameters can provide guidelines to effectively minimize wear in TKRs.