Usinagem da liga Ti6Al4V com aplicação de lubrificantes sólidos no torneamento

Abstract

The process of machining of difficult to cut materials such as titanium and its alloys has an important role in the development of new machining techniques, such as cutting tools and coatings, with the aim to increase the machinability of these materials. Due to the thermal properties of titanium, such as low thermal conductivity and high creep resistance, the cutting tool suffers accelerated wear, which affects the tool life. This paper describes a study of the use of solid lubricant during the machining of Ti6Al4V in a turning operation. TiAlN coated cemented carbide tool (grade S15) was used. Dry tests, flood, Minimum Quantity of Lubricant - MQL, and tests with lubricant with 20% by weight of solid lubricants: GR325 (graphite, maximum particle size of 40^m), GR625 (20^m), GR1000 (5^m) and molybdenum disulphide (MoS2, 5^m) were carried out. The parameters evaluated are: tool life, surface roughness, cutting forces, analysis of chips, chip thickness ratio and temperature of the interface (tool-work thermocouple). Tool flank wear, a major problem in machining of titanium alloys, was significantly reduced due to the action of the solid lubricants. Experimental results showed the superiority of molybdenum disulphide in relation to graphite in the turning process: reducing the tool wears, prolonging tool life, reducing cutting forces, improving surface roughness, reducing degree of chip deformation and decreasing the cutting temperature. The solid lubricant may be a viable alternative to dry and flood turning. Thus, it may be inferred that proper application of solid lubricants in machining of Ti6Al4V alloy results in reduction in tool wear, which can lead to enhancement of productivity.