Changes in Structure and Physicochemical Properties of Spark Coatings Based on TiN and TiB2 after Treatment with Concentrated Solar Radiation

Abstract

621.9.048Studies have been made on the structure and properties of spark coatings made of TiN and TiB 2 on steel U8 after treatment with concentrated solar radiation. It is found that the absorption capacity of the steel raised by a factor 2-3. The concentrated radiation reduces the coefficient of friction of the spark coatings made of TiN and TiB 2 by a factor 1.4, while the wear rate is reduced by a factor 1.6-2 by comparison with the untreated material.Concentrated solar radiation (CSR) used to treat protective coatings often considerably improves their physicotechnical characteristics [1,2]. Advantages of this method are the contactless heating in any medium or vacuum, clean heating, and scope for regulating the energy density over a wide range.Spark alloying (SA) produces surface layers with altered structure and composition as well as good adhesion. The method is simple, but one shortcoming is that it produces discontinuous rough coatings because of a discharge pulse discreteness. Therefore, to improve the properties, the SA coatings need additional treatment with focused solar radiation. This reduces the porosity, heals the microcracks, and improves the adhesion.Titanium nitride is a promising material for making wear-resistant coatings [3]. To reduce the brittleness of the titanium nitride electrodes and to increase the transfer factor, Cr and Ni are added, which form unrestricted solid solutions with the iron that is the basic element of the substrate. Adding Mo is used to increase the strength at high temperatures.Studies have been made [4, 5] on the structure and properties of coatings after SA with materials based on TiN, which have given erosion characteristics and electrode transfer coefficients. The purpose of the present study has been to examine improving the physicomechanical properties of spark coatings by treatment with concentrated solar radiation.Spark coatings on U8 steel were made with TiN − (Cr, Ni), TiN − (Mo, Ni), TiB 2 − (Mo, Ni) electrodes; all of the compositions included Al 2 O 3 . The SA was performed with an EFI-46A equipment with I = 1.5 A and C = 300 μF.The surface was treated with focused solar radiation in a SGU-2 equipment, which consisted of a mirror concentrating the solar energy fitted with a sun-tracking system. The radiation flux was regulated within the range 3000-4000 kW/m 2 by means of a blind. Tribological studies were performed with an MT-65 equipment with V = 10 m/sec and load P = = 0.5 MPa on a shaft-insert scheme in air by a standard method [6]. We recorded the frictional force, from which we calculated the coefficient of friction f and the linear wear of the friction pair, which gave the wear intensity I.X-ray diffraction was applied to specimens treated with focused solar radiation with a DRON-3M apparatus in CuK α radiation, while metallographic analysis of the spark coatings and the steel substrates employed an MIM-10 optical microscope.

Wear resistance of spark-deposited TiN, TiB2, and Mo coatings on 30KhGSA steel after exposure to focused solar radiation

“…However, nonuniform rough coatings are one of its drawbacks (because of discrete discharge pulses) [2]. To improve the physical and technical properties of spark-deposited coatings (roughness, porosity), focused solar radiation (FSR) should be used [3]. For obtaining wear-resistant coatings, TiN and TiB 2 are promising materials.…”

“…For obtaining wear-resistant coatings, TiN and TiB 2 are promising materials. To decrease the brittleness of electrodes from these materials, Cr, Ni, Mo, and Al 2 O 3 additions are introduced [3].The objective of this paper is to study the use of FSR to improve the mechanical properties of sparkdeposited coatings.We examined the structure and properties of spark-deposited TiN-(Cr, Ni), TiN-(Ni, Mo), and TiB 2 -(Ni, Mo) coatings on 30KhGSA steel. All materials contained Al 2 O 3 .…”

“…For obtaining wear-resistant coatings, TiN and TiB 2 are promising materials. To decrease the brittleness of electrodes from these materials, Cr, Ni, Mo, and Al 2 O 3 additions are introduced [3].…”