Journal of Materials Processing Technology 179 (2006) 124–127 Analysis of temperature during drilling of Ti6Al4V with minimal quantity of lubricant Rodrigo Panosso Zeilmann a,∗ , Walter Lindolfo Weingaertner b a University of Caxias do Sul, Mechanical Engineering Department, Rua Francisco Get´ ulio Vargas, 1130, Bloco D, Caxias do Sul RS, CEP 95070-560, Brazil b Federal University of Santa Catarina, Mechanical Engineering Department, Campus Universit´ ario-Trindade, CTC/EMC, Florian ´ opolis SC, CEP 88010-970, Brazil Abstract This paper presents a study of the temperature reached during drilling of the titanium alloy Ti6Al4V, employing class K10 carbide drills with and without hard coating (TiAlN, CrCN or TiCN). The main object of this study was to evaluate the temperature for different coated tools under the condition of application of minimal quantity of lubricant (MQL). The drilling process was chosen to evaluate the effect of the lubrication obtained with MQL, where the lubricant was applied either with an external nozzle or internally through the drill. The results show potential for drilling with MQL applied internally through the tool. For drilling with MQL applied with an external nozzle, the process was restricted to small depths and limited with reference to the requirements of the surface quality of the hole. © 2006 Elsevier B.V. All rights reserved. Keywords: Drilling; Coated drill; Temperature; Surface quality 1. Introduction In dry drilling or with minimal quantity of lubricant (MQL), the cooling obtained is either absent or is negligible compared to that obtained with normal quantities of cutting fluids (abundant). Consequently, the thermal behavior should be more pronounced, leading to more problems in a technology transfer from conven- tional machining with abundant lubricant to dry machining or with MQL [1–4]. To best understand the effect of a reduction in the quantity of lubricant it is necessary to evaluate the ther- mal behavior of the drilling process. The problem of elevated temperatures is more critical in the machining of titanium alloys that present inadequate thermal characteristics for chip remove. Several processes permit measurements of temperature in loco. The common measures employ thermograph, pyrometry, ther- moelectric measurements and calorimetry, but the most usual use thermoelements [5]. The measurement of temperature with thermoelements leads to excellent results [6]. In this process, one must be consider the thermal capacity of the thermoele- ments, the contact between the thermoelement and the object ∗ Corresponding author. E-mail addresses: RPZeilma@ucs.br (R.P. Zeilmann), wlw@emc.ufsc.br (W.L. Weingaertner). of measurement, as well as their response time [7]. For many years now, the definition of the thermoelement in practical indus- trial temperature measurements has been of great importance. Annually, millions of thermoelements are manufactured and, with the development of the electronic one, the characteristics of these were improved [8]. Recently, many papers have been pub- lished [5,4,1,9] on measurement of temperature in the machining process. Koppka [9] attempted to measure the temperature of titanium alloys at elevated cutting speeds. In this work, drilling temperatures in the widely used alpha–beta alloy Ti6Al4V were determined for several different lubricating conditions in order to study the utility of using MQL for these materials. 2. Experiments Plates of alpha–beta Ti6Al4V alloy (tensile strength R m = 970 N/mm 2 and hardness 300 HB) with dimensions 200 mm × 150 mm × 20 mm were prepared for these drilling experiments. Holes were drilled with 8.5 mm diameter drills through the smallest dimension using a vertical machining center. Special care was taken to hold the titanium alloy plates in place and we estimate the run-out in the initial position of the tool to be about 0.012 mm. Cutting fluids were applied with a pressure of 3.5 bar. Two types of drill were used in these experiments, all of carbide class type K10, micro grains, containing 9.5% of cobalt, with a clearance angle of 6 ◦ , diameter of 8.5 mm and three edges (type 125 drill with internal cooling hole and type 105 drill for cooling with external nozzle). Those drills having holes for internal lubrification were not coated. However, drills without internal lubri- 0924-0136/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2006.03.077