Tribological coatings for improving cutting tool performance B.L. Strahin a, ⁎, G.L. Doll b a Akron Research and Technology, Akron, OH, USA b The University of Akron, Akron, OH, USA abstract article info Article history: Received 12 June 2017 Revised 29 August 2017 Accepted in revised form 2 September 2017 Available online xxxx With an increasing usage of advanced high-strength steels, there is an escalating need for improvements in cut- ting tool performance for these alloys. In this study, the tribological performances of Cr 2 N, WC/a-C:H, and Ti- MoS 2 coatings on AISI M2 steel were examined. Surface treatments were evaluated using dry pin-on-disk testing, Charpy impact testing, and a reciprocating impact-sliding test rig (RISTR) designed to replicate the interaction between cutting tools and high-strength steel sheet. Charpy testing of coated specimens showed no statistical change in impact toughness from the untreated steel. Pin-on-disk testing was performed to quantify the friction and wear of untreated and coated tool steel. These tests showed that Ti-MoS 2 coated tool steel had the lowest friction coefficient, and Cr 2 N, the lowest wear rate. Impact tribometer testing showed that the Ti-MoS 2 coating yielded an increase of 370% in the number of cycles to failure over untreated specimens, while the WC/a-C:H coating was found to decrease the number of cycles to failure over untreated specimens. With an impact stress lower than the compressive yield strength of the AISI M2 steel, the fatigue life of the surface treatments scaled approximately as E 2 /H 3 , the inverse of the resistance to plastic deformation. © 2017 Elsevier B.V. All rights reserved. Keywords: Wear Impact Sliding Chromium nitride Titanium molybdenum disulfide Tungsten carbide amorphous hydrocarbon 1. Introduction 1.1. Background Years of industry experience have revealed a growing need for new advancements in industrial cutting tools. Advanced-high strength steel (AHSS) exhibits a combination of strength and ductility not seen in tra- ditional materials. Tool failures can cause costly downtimes in industry and can cause delays to first responders when cutting tools fail to cut through the AHSS frames used in modern automobiles [1]. Premature tool failure when cutting AHSS occurs from two primary mechanisms: increased wear and an increased risk of fracture [2]. This complicates the selection of cutting tool alloys because this must be balanced with the need for a higher strength material to shear the higher strength AHSS. Many manufacturers have used custom chemistries to obtain tooling that has a good combination of properties [3]. Success has also been seen when using tools manufactured from cermet, ceramic, and composite materials [4]. These materials can be very costly and lack the toughness required for cutting operations that see impact loading conditions. It was recently estimated that industrial cutting tools ac- count for about $8 billion annually in developed markets [5]. An alterna- tive to this approach is to engineer the surfaces of more common tool steels while providing the desired combination of wear resistance and strength in the cutting tool. Wear and damage on industrial tooling is caused by several different mechanisms. Theses mechanisms are adhesion, abrasion, diffusion be- tween the tool and workpiece, thermal gradients, load variations, and impact loading [6]. Tool wear consists of both physical and chemical re- actions and consists of approximately 50% abrasion, 20% adhesion, 10% chemical reaction, and 20% other [5]. Impacts to the tool cutting edge can cause cutting edge failure due to cracking, chipping, and plastic de- formation [6]. Typically, cutting tools that have cracked or chipped can- not be resharpened and must be discarded. Adhesion can best be explained as friction welding between the two materials during contact. Chemical reactions can be reactions between workpiece and cutting tool, with lubricant, or with atmosphere. Traditionally, coatings with high hardness and high thermal stability have been used to provide wear resistance to industrial tooling. Industry trend has been to increase hardness of tool coatings to increase tool life [7]. Titanium nitride, tita- nium carbide, and aluminum oxide are recommended for dry cutting due to the higher temperatures generated [5] but chromium nitride, titanium aluminum nitride, molybdenum disulfide, and amorphous hy- drocarbon coatings have also been used [8,9]. Shear blades do not typi- cally see the higher temperatures seen during dry machining and do not require coatings to combat this issue. Plasma nitriding has also seen some success in industrial cutting tools and has been shown to improve the percussive impact resistance of tool steels and decrease the adhesive wear due to sliding and impact [10]. Others have also shown that by re- ducing surface roughness and gas nitriding, the performance of lower cost steels can be improved enough to allow them to be used for tooling in place of higher cost materials [11]. However, these coatings are not Surface & Coatings Technology xxx (2017) xxx–xxx ⁎ Corresponding author. E-mail addresses: Brandon@AkronRT.com (B.L. Strahin), gd27@uakron.edu (G.L. Doll). SCT-22647; No of Pages 6 http://dx.doi.org/10.1016/j.surfcoat.2017.09.010 0257-8972/© 2017 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Surface & Coatings Technology journal homepage: www.elsevier.com/locate/surfcoat Please cite this article as: B.L. Strahin, G.L. Doll, Surf. Coat. Technol. (2017), http://dx.doi.org/10.1016/j.surfcoat.2017.09.010