Experimental study on impact fretting in heat exchanger tubes with brush plated coatings
The impact fretting wear of heat exchanger tubes with brush-plated copper, nickel and nickel-tungsten alloy coatings was experimentally studied. The test results showed that the wear rate of steel 10 specimens was highest, followed by copper coated, and those coated with a nickel and nickel-tungsten alloy, which performed best. The study suggested that tubes with a harder coating showed superior resistance to impact fretting wear. Scanning electron micrographs and metallographs clearly showed that the predominent wear process in this study was surface fatigue. 17 refs., 7 figs., 1 tab.
The paper deals with the example of application of the two continuum rheological model of materials with microdefects, nanodefects and solute hydrogen for calculation of stress and strain in cylindrical specimen under periodic loading. The model suggested allows one to relate the mechanical characteristics with the hydrogen concentration.The stability analysis of the system metal-hydrogen is carried out. The influence of parameters of the mechanical loading, hydrogen concentration and parameters of sorption and desorption of hydrogen from the surface of the internal defects (traps) of various nature on the system stability is performed.It is shown that influence of hydrogen can be considered as parametric instability of a continuous medium under mechanical deformation.This can be important during forming or plastic deformation of materials and nanomaterials containing hydrogen.