Abrasive wear of ZrB2-containing spark-deposited and combined coatings on titanium alloy. II. Nonfixed-abrasive wear of ZrB2-containing coatings

Abstract

The kinetics of nonfixed-abrasive wear of spark-deposited and laser-spark coatings on titanium alloy is studied. The coatings are deposited using electrode materials with different ZrB 2 contents. It is revealed that the wear rate of the coatings decreases with higher ZrB 2 content of the alloying electrode, after laser fusion, which increases the hardness of the outer layer, and with longer deposition of the coating, which increases its thickness It is shown that combined ZrB 2 -based coating can compete with spark-deposited WC + 3%Co coating.This paper continues the research [1] and focuses on the kinetics of the abrasive wear of ZrB 2 -containing coatings deposited with electrospark alloying (ESA) and combined laser-electrospark method. The ZrB 2 -containing electrode materials were developed at the Institute for Problems of Materials Science (National Academy of Sciences of Ukraine). Table 1 shows the numbers of the samples and compositions of the electrode materials.Tests for abrasive wear resistance were conducted in air with a NAUU friction machine ( Fig. 1) used to compare the wear resistance of materials and coatings during friction on a nonfixed abrasive. Our wear-resistance testing procedure corresponds to GOST 23.208-79 and is close to US standard ASTM G65-04. A 30 × 30 mm sample with a coating is pressed down with a rubber roll 50 mm in diameter, which rotates and supplies the abrasive to the contact area. The press-down force is controlled by loading. The tests were performed at a sliding speed of 0.163 m/sec and a load of 44.1 and 84.2 N. Quartz sand (SiO 2 ) with a grain size of 100-160 μm was used as an abrasive. The wear was measured gravimetrically to 0.0001 g. The volume wear was assessed taking into account the density of the material deposited. 436 3 4 5 6 2 1 Fig. 1. Friction machine with a nonfixed abrasive: 1) rubber roll, 2) sample, 3) feeder, 4) sand, 5) tray, 6) load Figure 2 shows the wear rate (I) of different ZrB 2 coatings on VT-20 alloy as a function of length (L) andtime (τ) of the process. The same dependences were obtained for VT-20 titanium alloy without coating (sample 1) and for spark-deposited WC + 3% Co coating (sample 2). The VK-3 electrode material is selected because the lowcobalt alloy has the highest abrasive wear resistance among WC-Co hard alloys [2]. The three-stage kinetic dependences I (L, τ) are typical of sliding friction [3] and show changes in polyoxide tribofilm in the 'abrasive particle-coating surface' contact area during abrasive wear. The first stage (L ≤ 100 m) is characterized by severe wear, in which a tribofilm forms. The uncoated VT-20 alloy has the highest surface wear rate at this stage, which is determined as tgα = I/L(τ). As the ZrB 2 volume content of the alloying electrode (Table 2) and of the coating increases, the wear rate decreases (Fig. 2). The L value, which corresponds to the 'severe wear → weak wear' transfer for the starting uncoated VT-20 alloy (~200 m) is twice as high for the coatings (~100 m); i.e., a tribofilm over the coatings f...

Structure and phase composition of composite detonation coatings based on TiCrB2 and ZrB2

“…This conclusion is based on our previous research into the properties of spark-deposited [10] and plasma [11] coatings based on titanium and zirconium borides.…”

Application of AlB$_{12}$–Al Electric Spark Coatings to Protect Titanium Alloys During Wear Under Fretting Corrosion

“…The analysis of causes of wear and technological methods of hardening surface treatment of friction parts shows that in many cases the problem of increasing their wear resistance is solved by modifying the working surfaces by electrospark alloying (ESA) [6][7][8][9][10][11]. This method, characterized by technological simplicity and low power consumption, allows to form on metal substrate surface-strengthened layers with high wear resistance and the strength of adhesion of the deposited coating with the base.…”