Metal adhesion issues in dry grinding: The role of active fillers L. Vernhet a,b , C. Minfray a,n , C. Delwaulle b , T. Le Mogne a , P. Kapsa a a Université de Lyon, Ecole Centrale de Lyon, Laboratoire de Tribologie et Dynamique des Systèmes, UMR CNRS 5513, Ecully, France b Saint Gobain CREE, Cavaillon, France article info Article history: Received 16 July 2015 Received in revised form 1 November 2015 Accepted 3 November 2015 Available online 10 November 2015 Keywords: Steel Engineering ceramics Other manufacturing processes Electron microscopy Surface analysis abstract The dry grinding of metals is a common machining operation. The main issue with such techniques is metal adhesion on the abrasive tool, which decreases the material removal rate. In this work, the effect of active filler metal loading with materials such as cryolite and KBF 4 , which are present in the resin of commercial abrasive belts, was studied. Grinding belt experiments and friction tests were performed with carbon and stainless steel and with belts containing zirconia-reinforced-alumina grains, as well as active fillers. The tests were followed by SEM-EDX, TEM or XPS characterizations of the belts and ceramic pieces. Different behaviors were observed for different types of metal, as stainless steel is more sensitive to loading than carbon steel, and because active fillers have a stronger positive effect against metal adhesion, such as in the case of stainless steel. Then, a fluorine based layer, derived from the active fillers, was found at the interface between the grain and the metallic transfer. This layer likely limits the adhesion of metal on the grain and decreases the contact friction, as well as the specific grinding energy (SGE). The corrosion of alumina in the abrasive grains by active fillers was also observed near contact temperatures. Finally, the results are discussed to gain a better understanding of different active filler action mechanisms taking place during the steel grinding process. & 2015 Elsevier B.V. All rights reserved. 1. Introduction For dry grinding metals, the cutting efficiency of an abrasive tool is related to the mechanical properties of the abrasive grains. The grains need to be well adhered to the support and need to be much harder than the material being ground to easily remove the metal through abrasive wear (plastic deformation) [1]. The cutting effi- ciency can decrease because of the blunting of grain edges or metal adhesion. When these processes occur, grain fracture is required to yield new sharp cutting edges. Finally, hard materials with optimized fracture toughnesses are often used as abrasive grains [2]. Ceramic grains such as alumina, alumina–zirconia composite, diamond, SiC, etc. are commonly used in such applications [2]. One of the main issues in grinding processes is metallic transfer on the abrasive tool. This metal may come directly from the machined steel or from metal chips emitted during the cutting operation. Adhesion of the metal to the ceramic then occurs. Because the plastic flow stress of the metal is much lower than for the ceramic, metal transfer is formed on the ceramic grain [3]. This fouling of the tool results in a significant decrease in cutting effi- ciency, which is associated with an increase in the required energy to machine. According to the nature of the steel being ground, this phenomenon varies in importance. Metal adhesion must be limited on abrasive tools to ensure that the tool retains its grinding capacity. In this work, a belt grinding tool is considered. This abrasive tool consists of a backing, a coating and ceramic grains. The coating is usually made of a polymeric resin with fillers such as cryolite, KBF 4 or CaCO 3 . Different patents are mentioning for the types of fillers [4–6]. CaCO 3 is known to reinforce the mechanical behavior of the resin as the temperature increases. Cryolite (Na 3 AlF 6 ) and KBF 4 are employed for the role they play in the frictional behavior of the metal/grain interface [7,8]. In this work, it is proposed to investigate in detail the roles of active fillers during grinding operations. Several questions that we will address include: Are they lubricating the contact? Are they corroding the metal? Are they corroding the grains? Are they limiting the temperature at the contact (by endothermic reactions for example) [9]? Are their actions the same for different metals? To answer such questions, the effect of active fillers is studied on the grinding efficiency in two ways: (1) First, performing an “industrial” test to mimic real conditions and referred to here as a belt grinding test. Mechanical mea- surements are performed during the experiments and post-mortem analyses of the worn belts are also performed. (2) Second, tests on a specific tribotest are developed and per- formed to investigate the role active fillers have on the tri- bological properties of the grain/steel contact. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/wear Wear http://dx.doi.org/10.1016/j.wear.2015.11.002 0043-1648/& 2015 Elsevier B.V. All rights reserved. n Corresponding author. Tel.: þ33 472186336; fax: þ33 478433383. E-mail address: clotilde.minfray@ec-lyon.fr (C. Minfray). Wear 346-347 (2016) 46–55