Effect of Complex Magnetic-Abrasive and Chemical-Thermal Treatment on the Fatigue Resistance of VT8 Alloy Compressor Blades

The results of studies of the effect of complex magnetic-abrasive (MAT) and chemical-thermal (CTT) treatment on the fatigue resistance of compressor blades made of VT8 alloy are presented. The CTT method of the titanium alloy surface is a method of nitrocementation, which consists in the simultaneous saturation of the blade surface with carbon and nitrogen in a gas environment. Prior to that, MAT of blades were carried out to form favorable residual stresses in the surface layer, which stimulate the CTT process, provide its higher efficiency, productivity and the ability to create a diffusion layer of the required depth and quality. The results of measurements of microhardness of the surface layer of the blades in the initial state and after complex treatment are presented. The analysis of measurements showed that the microhardness of the initial blade tends to decrease steadily with small fluctuations to a depth of 0.25 mm, while on the blade after complex treatment by MAT+CTT+MAT we have three hardness peaks with higher values than the initial blades to a depth of 0.15 mm. The effect of complex treatment by technological cycle of MAT+CTT+MAT was estimated according to the results of comparative fatigue tests of VT8 alloy blades in the initial state and after treatment. It is shown that due to the formed reinforced layer on the surface of the blades after treatment, which has greater microhardness and microhardness gradient along the blade depth, the scattered damage accumulation under cyclic loading slows down, whereas the endurance limit of these blades based on N = 107 cycles is 14% higher than the endurance limit of the blades in the initial state.