Friction surfacing of different substrates with different co

Friction surfacing of different substrates with different coating combinations, consisting of hard coatings on soft substrates as well as soft coatings on hard substrates [5,6] and coating of metal matrix composite on aluminium–silicon alloy to improve wear resistance [7], is some of the recent studies. Intelligent support systems have also been reported to have been employed for optimizing friction surfacing parameters [8]. Steels are coated with zinc or aluminium to protect them against atmospheric corrosion [9]. Aluminium is used as anode for the protection of ships by sacrificial anodic protection of steel parts of marine vessels, especially of war ships, exposed to sea water [10]. Aluminium deposition on mild steel by fusion welding is not feasible as it bun hot chemically reacts to form iron aluminide, and Fe and Al are immiscible. Hence, a solid state deposition is a possible option. The present study deals with deposition of AA 6063 aluminium alloy on IS2062 mild steel substrate. Detailed characterization of these solid state deposits of aluminium on mild steel has not been well documented, thus, the present study assumes special significance. In the present study, the factorial design of experiments [11] has been selected to investigate the influence of friction surfacing process parameters on the physical dimensions of the coating, namely coating width and thickness with adequate strength and ductility.
Experimental procedure AA 6063 aluminium alloy of 15 mm diameter and 280 mm long rod was taken as mechtrode (consumable rod), and IS2062 mild steel of 250 mm × 300 mm × 10 mm plate was used as substrate. The chemical composition and mechanical properties of mechtrode and substrate are shown in Tables 1 and 2, respectively. Rod end was machined to ensure flatness, and the substrate was milled and its surface was grinded to obtain a flat and even surface free of oxide. Mechtrode and substrate were cleaned with acetone prior to surfacing to minimize the contamination. Experiments were carried on CNC Friction Surfacing machine with a capacity of 50 kN axial force (F), spindle speed 2400 rpm (N) and table speed of 5000 mm/min(Vx) in the Defence Metallurgical Research Laboratory, Hyderabad, India with the option to conduct experiments either in force controlled or position controlled mode. In the present study, the experiments were conducted in force controlled mode. AA6063 aluminium alloy coatings were deposited on mild steel for 100 mm in length as per the experimental parameter matrix [12] details given in Table 3.
Characterization of coatings AA6063 aluminium alloy coatings on mild steel obtained with eight different parameter combinations are shown in Fig. 3(a). The coatings exhibited ripple formation with spacing between the ripples. Coating width and thickness were observed to depend on the surfacing parameters, coating widths of advanced side and retreating side were machined to observe effective contact area and sectioned for measuring the effective coating width and thickness in contact with substrate [13]. Physical dimensions of the coating, namely coating width and thickness, were measured from their stereo micrographs obtained after conventional metallographic sample preparation of transverse sections of the samples, as shown in Fig. 3(b) and (c). A ram tensile test similar to Mil-J-24445A was designed in order to determine the interfacial strengths of the coating and the substrate, as shown in Fig. 4. For this, the coating material was machined from the substrate as a circular area forming an inner circle without the coating while retaining the outer circular area to form an annular space consisting of intact coating and substrate. The outer circle coating was machined to facilitate to support the substrate on a fixture such Coding strand part of the inner circular area in the annular space is only subjected to loading under loading on the area. The test was conducted on a 100 kN INSTRON universal testing machine. Ram tensile test samples are shown in Fig. 5.