Material Flow Visualization during Friction Surfacing

Abstract

Metal flow behavior within friction surfaced coating was studied using tungsten powder as a marker. The results show that the top and bottom layers within the coating exhibit distinct flow patterns. The transport of material takes an involute path, and the material transfer starts from the advancing side of the coating to the retreating side and terminates at the center. The recirculation of material occurs at the retreating side of the coating.Friction surfacing is an emerging technique for producing thick solid-state coatings to combat wear and corrosion. In this process, localized heating is produced by the friction generated between the rotating consumable rod and the substrate. The rubbing surface of the consumable rod undergoes intense plastic deformation at elevated temperatures, resulting in the formation of hot plasticized material, which is transferred into the substrate to form the coating. The material is transferred in successive discrete layers, which constitute the coating. [1] A typical stainless steel friction surfaced coating is shown in Figure 1. Many studies have been carried out on the feasibility of depositing a variety of materials on different substrates. [2][3][4] However, studies on fundamental aspects of friction surfacing are very limited, particularly on metal flow behavior during friction surfacing. [5,6] Friction surfacing involves a combination of stirring, extrusion, and forging. Hence, a simple analytical description of metal flow behavior is difficult. In this study, a marker technique is adopted to visualize the metal flow patterns in the coating during friction surfacing. The transverse cross sections of the coated regions were studied with X-ray radiography and scanning electron microscopy (SEM).The consumable material used for this study was stainless steel AISI 304, and the marker material used was tungsten powder. Two rods, 18-mm diameter and 100-mm long, were used for producing the coating.Eight holes, 1.5-mm diameter, were drilled along the periphery of the rubbing surface of one consumable rod, and a 3-mm hole was drilled at the center of the second consumable rod (Figure 2). These holes were filled with tungsten powder prior to friction surfacing. X-ray radiography was conducted from the top surface of the as-deposited coatings, while the transverse cross section of the coatings was examined in the unetched condition with scanning electron microscopy in the backscattered electron (SEM-BSE) mode. Figures 3(a) and (b) show the X-ray radiograph of the coating produced with marker at the center and periphery, respectively. The distribution of tungsten powder at the starting and the middle regions of the coating is to be noted carefully. At the starting region, the location of markers corresponds to the same position as originally placed in the consumable rod. However, when the coating proceeds, there is a difference in the location of markers, which can be accounted with two stages of the coating process: (1) dwell period at the start, where the consumable rod is allowed t...

Application of Friction Surfacing to the Production of Aluminum Coatings Reinforced with Al2O3 Particles

“…The plasticized metal is transferred in discrete layers in an elliptical form and each layer gets deposited one after other. Such a characteristic is also found in the results shown by Gandra et al 16 and Rafi et al 4 , indicating that the union process on the substrate occurs from the retreating side to the advancing side. Table 3 shows the control parameters used in FS and also the average lengths (L), widths (W) and thicknesses (T) of the deposits for each condition.…”

“…The heat from the contact between the consumable rod and substrate generates a viscoplastic metal layer at the rod tip, where the material is transferred to the substrate in discrete layers of an elliptical shape. In the FS process, the conditions of pressure and temperature lead to an interdiffusion process resulting in the bonding of the material from the consumable rod to the substrate [1][2][3][4] . One of the advantages of FS is the production of coatings with a fine microstructure, which show good wear and corrosion resistance.…”

Friction surfacing—A review

“…(a) AISI H13 over AISI 1020 (Rafi et al, 2010a), (b) AA2017 over AA5052 (Tokisue et al, 2006), (c) AISI 310 over AISI 1020 (Rafi et al, 2010b). centre (Rafi et al, 2011b). Fig.…”

“…Top view X-ray radiographs revealing tracer distribution. Hole filled with tracers was placed at rod centre (Rafi et al, 2011b). Fukakusa (1996) also studied the plastic flow in FS using a tracer technique.…”

Assessment of Process Parameters by Friction Surfacing on the Double Layer Deposition

“…This characteristic is influenced by the deposition control of the process, due to the axial force applied or by the consumable rod feed rate. Consequently, the deposition control determines the material flow during the process both in the rotation level (contact between the consumable rod and the top of the deposit) and in the translation level (contact between the substrate and the bottom of the deposit) 11,12 . In this article, from Figure 4, in the deposition process 3B controlled by the consumable rod feed rate of 5.5 mm/s (Table 1), there was a significant decrease in the occurrence of undercut at the edges of the deposits, when compared to depositions 1B and 2B.…”