Wear Properties of TiN Coating on AISI M2

Application of hard coatings to improve the resistance of tooling to withstand adhesive and abrasive wear underwent a significant development program within the past decades. Surface hardening treatments used in the metal-mechanic industry generally fall into two categories, diffusion (carburizing, nitriding, boriding, and carbo-boro-nitriding) and overlay coating (TiN) [1-6]. A hard layer on a soft surface can reduce friction and wear by preventing fissuring at both the macro and the micro-level. Such a layer typically has residual compressive stress, which can prevent the occurrence of tensile forces. A further reduction of friction and wear can be achieved by increasing the stiffness of the carrying load by increasing the hardness of the substrate, which inhibits the deflection and fissuring resulting from the load of the countersurface. In this regard, Physical Vapor Deposition (PVD) coatings present advanced properties such as high hardness, high melting point, low friction coefficient, high wear resistance, chemical stability, and corrosion resistance. Uses of these coatings can be found in the metal-working industry, biomedical applications, micro-electronics industry and for decorative purposes [7-11]. The current work aimed to analyze the microstructure of the TiN coating on AISI M2 high-speed steel produced by powder metallurgy is seen as a possibility of a reduction in the rate of crack propagation. Finally, the pin-on-disc tests were employed to carry out a comparative study between the TiN + AISI M2 and substrate in terms of wear behavior. The specimen sizes are following MPIF STANDARD 41, the tested samples had a disc shape with a diameter of 25.4 mm and a thickness of 10 mm. The chemical composition of the material is: 0.80% C, 4.13% Cr, 1.00% Co, 0.30% Mn, 5.00% Mo, 0.45% Si, 1.90% V, and 6.50% W (weight %). Figure 1 shows the cross-sections by SEM for the AISI M2. The three samples were cleaned using sputtering etching with 650 V, 240 kHz, 1600 ns for 15 min. The TiN coatings (see Figure 2) were obtained by using a target with high power impulse magnetron sputtering (HIPIMS) with 2000 W, 500 Hz, 200 ns and three targets with direct current magnetron sputtering (DCMS) with 2500 W on each (see Figure 3). The sputtering targets were Ti ( > 99.8%). Interlayers of pure Ti were deposited with 400 V bias-voltage on all substrates. TiN coatings were deposited by using bias-voltages of 75 V and 150 V. The TiN coatings had thicknesses of approximately 1 μm and 2 μm. The coatings were deposited at 450°C with a