Evaluation of Tribological Characteristics of Electric-Spark Coatings Prepared on Steel with Electrode Materials of the System TiN - Ni

Abstract

621.9.048The tribological and physicomechanical indices of electric-spark coatings of the system TiN − Ni are studied in relation to the phase and structural state of the electrode material. It is established that the optimum tribological properties are exhibited by TiN + (20-40)% Ni material due to forming a eutectic structure consisting of hard intermetallics and a ductile solid solution. It is shown that the ductile component (nickel) makes it possible to deform the coating material without embrittlement.In order to provide good operating reliability for machines and to increase their service life new composite materials are required with high antifriction properties. Titanium nitride with added metals is a promising material. Pure titanium nitride does not provide sufficient coating thickness and continuity due to its low affinity with steel [1]. A stable bond with a steel substrate and a strong coating of considerable thickness forms with nickel [2].The aim of the present work is to study the dependence of tribological properties (wear resistance and friction coefficient) for electric-spark coatings on the phase composition and structure of electrode materials TiN + (1-100)% Ni.The alloying electrodes were prepared by compaction and sintering in a travelling hearth furnace in an argon atmosphere at 1400-1700°C. Electric-spark alloying (ESA) of steel was accomplished in a ÉFI-46A unit (working current strength I w = 1.25 A, C = 350 μF, open-circuit voltage U o.c = 15 V). Metallographic analysis was performed in a Neophot-2 instrument, and x-ray phase analaysis was performed in a DRON-3 in copper and cobalt radiation. Tribological properties were determined in a M-22M device [3] that made it possible to record the coefficient of friction f and wear intensity I of a specimen during an experiment. Tests were carried out in air by a sleeve-shaft scheme without supply of lubricant to the contact zone in a pair with steel KhVG with a sliding rate V = 0.5 m/sec and pressure P = = 2.0 MPa.The phase composition of the electrode material has the most effect on alloyed layer properties (Table 1). According to the results obtained formation of oxides and solid solutions has a different effect on strengthened layer formation. It was established by x-ray phase analysis of TiN − Ni electrode materials that nickel and titanium form solid solution and intermetallic in accordance with the phase diagram for TiN − Ni [4]. The phase composition of TiN − Ni materials has been studied in [5]. These are solid solutions of titanium in nickel, intermetallics Ti 2 Ni, TiNi 3 , nonstoichiometric TiN 1−x ( Table 1). As a result of titanium nitride dissociation [2] there is formation of non-stoichiometric TiN 1−x and a solid solution of titanium in nickel typical for all compositions containing the metal binder. Formation of * Deceased.

A novel method of preparation of metal ceramic coatings

“…There are many methods used for preparation of ceramic coatings to the surface of metal materials, such as plasma spray, laser cladding, vapor deposition, etc. Among these methods, plasma electrolytic deposition (PED) (Nie et al, 2001;Matthews et al, 1999) and electric spark discharge (ESD) (Puastovskii et al, 2002(Puastovskii et al, , 2005 are the better ones due to inapparent heating of the substrate materials during processing and metallurgically bonded coat- * Corresponding author. Tel.…”