Determination of Discrete-Structure Parameters of Coatings with Allowance for Residual Stresses

The authors suggest that the dimensions of a discrete section of a coating should be chosen on the basis of calculation of the critical crack spacing in cohesion cracking. This approach allows for residual stresses in the coating. The reliability of the calculation method has been verified experimentally by direct measurement of the crack spacing.     

Fatigue of VT20 titanium alloy with vacuum-plasma coatings at high temperatures

We study the influence of vacuum–plasma TiN, (TiAl)N, and (TiC)N coatings on the high-cycle fatigue of VT20 titanium alloy in the temperature range 350–640°C for a loading frequency of 10 kHz. It is shown that, in this temperature range, the fatigue limits of VT20 alloy with the indicated coatings 6 μm in thickness become 15–25% higher than for the material without coating. The possibility of replacement of steel blades with titanium blades with vacuum-plasma coatings is demonstrated. Translated from Problemy Prochnosti, No. 4, pp. 101–107, July–August, 2009.     

On the Reduction of Residual Stresses in Plasma-Vacuum-Deposited Coatings

Residual stresses in a plasma-vacuum-deposited titanium-nitride coating, which vary between –780 and –2800 MPa depending on the coating thickness, have been determined. It has been shown that deposition of a pure-chromium sublayer and substitution of a discontinuous (discrete) coating for a continuous one allow residual stresses to be reduced appreciably. It has been found that residual compression stresses can affect favorably the characteristics of strength of both the coating itself and the coated part as a whole.