Structure and properties of electric-spark alloyed TiN, TiB 2 , and Mo coatings on VT22 titanium alloy and their transfo
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STRUCTURE AND PROPERTIES OF ELECTRIC-SPARK ALLOYED TiN, TiB 2 , AND Mo COATINGS ON VT22 TITANIUM ALLOY AND THEIR TRANSFORMATION UNDER LIGHT-THERMAL TREATMENT O. V. Paustovs’kyi,1 V. V. Pasichnyi,1 I. I. Tymofeeva,1 O. H. Molyar,1, 2 V. I. Novikova,1 V. E. Shelud’ko,1 N. M. Mordovets’,1 S. O. Ostapenko,1 O. D. Kostenko,1 and L. P. Isaeva1
UDC 682.9.048
We have established that electric-spark alloyed TiN, TiB2 , and Mo coatings improve substantially the tribotechnical characteristics of VT22 titanium alloy. It has been shown that an increase in the slip velocity from 1.0 to 10 m/sec increases the wear intensity and friction coefficient by a factor of 1.5–2 and 1.3, respectively. A significant amount of oxides in the coatings and their additional alloying with titanium after treatment by concentrated solar radiation favor a 3–4 times increase in the layer thickness but lower its tribotechnical properties. Keywords: electric-spark alloying, current, solar treatment, coating, hardness, layer.
Electric-spark alloying (ESA) enables one to form surface layers with changed structure and composition and good adhesion to the base metal. This method is simple technologically, but it has a shortcoming, namely, the formation of nonsolid rough coatings due to pulse discreteness. Therefore, for improving the properties of the surface, it is reasonable to subject ESA-coatings to additional treatment, e.g., by concentrated solar radiation (CSR), which will enable one to decrease their porosity, to heal microcracks, and to improve adhesion [1, 2]. Among the advantages of this method, we should mention noncontact heating in any medium or vacuum, heating purity, the possibility of regulation of the density of input energy over a wide range, and pressure absence. Commercial titanium alloys, which, according to their structure, are divided into -, + -, and -alloys [3], possess high physicochemicomechanical properties, which determines their application in aerospace industry. Among them, VT22 ( + )-alloy has the highest strength ( u = 1200 ), but its wide application is hampered by low tribotechnical characteristics, which is inherent in all these alloys [4]. Therefore, improvement of the tribotechnical properties of titanium alloys, in particular, by applying protective coatings, represents an important scientific problem. For its solution, we applied ESA-coatings of TiN, TiB2, and on VT22 titanium alloy. Earlier [5], we have shown the possibility to enhance the hardness and wear resistance of ESA-coatings of TiN and TiB2 on U8 steel after CSR. The aim of this work is to study the possibilities of CSR for improving the physicomechanical properties of initial ESA-coatings applied on VT22 titanium alloy. Objects and Procedure of Tests For our investigations, we chose ESA-coatings of TiN + Cr, Ni; TiN + Ni, Mo; TiB2 + Ni, Mo as well as of molybdenum, applied on a substrate of VT22 alloy. We added Al 2 O 3 to all materials with refractory com1
Frantsevych Institute for Problems of Materials Science, Ukrainian National Acad
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