Contents lists available at ScienceDirect Wear journal homepage: www.elsevier.com/locate/wear Tribology of FeVCrC coatings deposited by HVOF and HVAF thermal spray processes Giovanni Bolelli a, ⁎ , Marcello Bursi a , Luca Lusvarghi a,b , Tiziano Manfredini a,b , Ville Matikainen c , Rinaldo Rigon d , Paolo Sassatelli a , Petri Vuoristo c a Department of Engineering “Enzo Ferrari”, University of Modena and Reggio Emilia, Via Pietro Vivarelli 10/1, 41125 Modena (MO), Italy b Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Local Unit Università di Modena e Reggio Emilia, Via Pietro Vivarelli 10/1, 41125 Modena (MO), Italy c Tampere University of Technology, Faculty of Engineering Sciences, Laboratory of Materials Science, Korkeakoulunkatu 6, Tampere, Finland d ECOR Research SpA, Via Friuli 11, 36015 Schio (VI), Italy ARTICLE INFO Keywords: Coating: thermal spray coatings Sliding wear Two-body abrasion Hardness ABSTRACT This work studies FeVCrC-based coatings as potential alternatives to conventional Ni- and Co-based alloys for wear protection. Specifically, the microstructure and tribological properties of the coatings are characterized as a function of the particle size distribution of the feedstock powder, of the deposition technique – High Velocity Oxygen-Fuel (HVOF) or High Velocity Air-Fuel (HVAF) spraying – and of specific processing parameters. HVOF-sprayed coatings obtained from fine feedstock powder exhibit numerous oxide inclusions, which provide high hardness (≈ 900 HV 0.3 ) but do not excessively impair fracture toughness, as determined through scratch testing techniques. HVAF-sprayed coatings obtained from the same feedstock powder contain much fewer oxide inclusions, and some of them possess simultaneously high hardness and high toughness. Defects (e.g. speckles) are instead formed in case unsuitable HVAF torch hardware is employed. A coarse feedstock powder always results in unmelted inclusions, which impair the cohesion of the coatings, particularly of the HVAF- sprayed ones. Most coatings anyway exhibit very low sliding wear rates < 3 × 10 -6 mm 3 /(N m); abrasive grooving and surface fatigue-induced pitting are the main wear mechanisms. Oxide inclusions do not affect negatively the response of HVOF coatings, whereas too many unmolten particles increase pitting under severe test conditions. Rubber-wheel abrasion testing produces comparatively more severe grooving. 1. Introduction Fe-based alloys have recently attracted considerable interest as materials for the production of wear-and corrosion-resistant coatings. On the one hand, Fe as the main alloy constituent is a relatively inexpensive material, particularly when compared to elements such as Co [1], which is the basis of many hardfacing alloys currently on the market (Stellites, Tribaloys, etc.) [2,3]. The latter has also been re- garded as a critical raw material at least since the 80's [4], the concern having grown in recent years [5–8] due to factors such as supply scarcity combined with strategic importance. Cobalt is indeed a key constituent not only of hardfacing materials, hardmetals, and heat-re- sistant alloys for aeronautical and energy production applications [2,3,9,10], but also of batteries and catalysts [6,8,9,11]. On the other hand, alloy constituents such as Ni and Co are toxic, allergenic elements, especially hazardous for human health when in inhalable powder form [12–14]. Handling of powdered feedstock ma- terials therefore requires additional risk management procedures at the workplace; a second, subtler risk might be envisaged in case solid Ni- or Co-based materials (included coated mechanical parts) release fine wear debris during service. Most of the research, as inferable from a representative sample of the recent literature [15–24], is concerned with Fe-Cr-C [17,23] or Fe- Cr-B(-C) [18–22,24] coating systems, either in (nano)crystalline [18,23], glassy [15,19,20], or composite (glass + nanocrystals) [24] form, processed by thermal spraying [17,19–21] or by cladding [16,22,23]. Cladded layers can be grown up to several millimeters in thickness, they are dense and metallurgically bonded to the substrate [3,10,25]; hence, they are well suited to the most severe wear and corrosion conditions. Depending on whether a hypo- or hyper-eutectic composi- tion is employed, their relatively coarse microstructure comprises either http://dx.doi.org/10.1016/j.wear.2017.10.014 Received 17 July 2017; Received in revised form 24 October 2017; Accepted 25 October 2017 ⁎ Corresponding author. E-mail address: giovanni.bolelli@unimore.it (G. Bolelli). Wear 394–395 (2018) 113–133 0043-1648/ © 2017 Elsevier B.V. All rights reserved. MARK