The Effect of Nb Supplement on Material Characteristics of Iron with Lamellar Graphite

In this experiment a cast iron alloy consisting of 0.019, 0.151, 0.431, and 0.646% niobium by weight was set and the microstructure solidification of iron with lamellar graphite was provided. These alloys were subjected to an abrasion test and chemical analyses of the microstructure were done by using scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). In addition to this, phase compositions were characterised by X-ray diffraction (XRD). Tests of mechanical strength, hardness, and tension were also applied to the alloys. The results of this experiment demonstrated that the addition of niobium to iron with lamellar graphite caused an increase in the abrasion resistance by 15%. This experiment shows that adding niobium improves the mechanical properties of grey cast iron. 1. Introduction More than 90% of the cast iron in industry consists of iron with lamellar graphite. High compression strength, high thermal conductivity, ability to isolate vibration, better machinability than other cast irons, good mould filling ability, and relatively low costs (lower than 20–40% of the cost of steel) are the main reasons for the extensive usage of iron with lamellar graphite in industries such as the automotive industry. Iron with lamellar graphite can be used as clutch covers and pressure plates in the automotive industry because of its good friction properties, as well as for engine blocks, brake discs, flywheels, cylinder sleeves, and piston rings [1–6]. Lamellar graphite cast iron shows great strength and abrasion resistance when used as a cylinder sleeve [7]. To improve the abrasion resistance of cast iron, some early works describe various aspects of small additions of niobium (<0.5%) [8–12]. These works have found minor changes to the austenite stability, refining of graphite structure, very small precipitations of Nb(C, N), and so on. Some of these investigations were misinterpreted or misunderstood, possibly due to the lack of advanced measuring techniques such as high-resolution microscopy as well as an incomplete understanding of the basic thermodynamics. Therefore, in this study, the effect of the addition of niobium on the mechanical strength and abrasion resistance of grey cast iron was investigated. 2. Experimental Study and Preparation of Samples Table 1 shows the chemical analysis of alloys A, B, C, and D, which were cast separately at 1450°C into sand moulds 150？mm high and 30？mm in diameter after being melted in a medium-frequency induction melting furnace. During casting, 0.1% strontium-based inoculation material was