Estudo da influência das condições de dressagem na integridade da superfície da liga Ti-6Al-4V

Abstract

Titanium alloys have a unique combination of properties that make them used mainly in the aeronautical industry. Some aeronautical engine components, such as blades, among others, are subjected to the grinding process at the end of their production chain, due to the need for high surface quality. However, titanium alloys are materials of difficult machinability and thus, the correct selection of operational parameters is essential. By considering that dressing is an essential operation for grinding, which defines its purpose and the surface integrity of the ground parts, the correct selection of dressing parameters is equally important. Nevertheless, there are few studies available in the literature that seek to evaluate the effects of dressing on titanium alloys grinding. In this sense, the present work aims to evaluate the effects that different dressing conditions of silicon carbide (SiC) grinding wheel play on the Ti-6Al-4V alloy grindability, in comparison with the effects provided by different radial depths of cut. Therefore, as input parameters two types of dressers were used (fliesen and single diamond tip), two overlap ratio (Ud = 3 and Ud = 12), two dressing infeed (ad = 20 µm and ad = 40 µm ), which were used in the dressing of a SiC grinding wheel (#46), and three radial depth of cut (ae = 10 µm, ae = 20 µm, and ae = 30 µm) used throughout the peripheral surface grinding tests on of Ti-6Al-4V alloy samples. As a results, the change in grinding wheel conditioning from a coarse condition (fliesen dresser, Ud = 3 and ad = 40 µm) to a smooth condition (single point dresser, Ud = 12 and ad = 20 µm) provided a reduction of 54.62%, 41.34% and 49.25% in roughness Ra, Rt, and Rz, respectively as well as improved the texture of ground surfaces and ensured a short deviation in microhardness (4.75%) concerning the reference, even reducing the extent of this variation to 120 µm below the grinding interface; this change also eliminated evidence of microstructural damage, allowed a reduction in energy consumption by up to 24.33%; generated a 96.85% drop in macro effects, as well as a reduction in micro effects generated on the grinding wheel's cutting surface and, in terms of the G ratio, the change in the degree of coating from Ud = 3 to Ud = 12, caused an increase up to 65.33%. Also according to the analysis of variance, when radial depth of cut is examined in isolation from other independent variables it did not influence the results, unlike when it was analyzed in combination with the degree of overlap ratio that, similar to the other dressing parameters, it has a significant influence about the results. Therefore, the dressing condition of the SiC vii grinding wheel capable of improving of Ti-6Al-4V alloy grindability is the use of a single-point dresser, combined with Ud = 12 and ad = 20 µm, regardless of radial depth of cut.