Abrasive Wear Studies Of Pack Cyanided Mild Steel (PCMS)

ABSTRACT

This work aimed at using processed cassava leaves to pack cyanide mild steel (MS) under different treatment conditions and investigating the wear properties of the pack cyanided mild steel (PCMS). Pack cyaniding (PC) of a MS was achieved using processed cassava leaves powder with BaCO3 as energizer in the heat treatment process. Four different powder particle sizes were utilized at four different temperatures (750oC, 800oC, 850oC and 900oC) and soaked for 3 hours. In this present work, the microstructures of the un-treated sample and PCMS were characterized to know the cases formed. The abrasive wear tests of the PCMS were carried out using a pin-on-disk wear tester against untreated mild steel pin having a hardness of 197.5 VHN. The PMSs wear properties were evaluated, using abrasive velocity of 0.26 m/s, normal load of 20 N, total abrasive distance of 156 m and controlled room temperature of 25 ◦C. The effect of particle size (212, 300, 600 and 850 µm) on the hardness and wear properties of a series of PCMS treated at different temperatures has been studied in this work. Case hardness was observed to decrease with a decrease in particle size and decreasing pack cyaniding temperature (PCT). Results revealed that the case hardness of the heat treated steels is related to the pack cyaniding temperature and the particle size used. The PCT of mild steel in cyaniding boat has a significant effect on the case hardness of the steel. Also, the wear test results indicated that the wear rate of treated mild steel increases with increasing PCT and particle size. The study concluded that case hardness and wear resistance of mild steel parts could be improved by pack-cyaniding in pulverized dry cassava leaves. 1 CHAPTER ONE 1.0 INTRODUCTION It is an undisputable fact that iron and steel are the most widely used engineering materials in industries. MS possesses the unique combinations of good mechanical properties and toughness but poor resistance to wear [1]. When the contact surfaces of these materials are subjected to relative motion, they undergo material removal known as wear. Thus their surface modification is necessary to improve their tribological behaviour. Therefore, there is the need to minimise friction and wear in order to extend the lifespan of these components. Although, several methods have been used to engineer the surface of these engineering components, they are more expensive and cumbersome. For example, diamond deposition [2, 3] on various non-diamond substrates has been well achieved and established. The problem this has is the difficulty in depositing the diamond on ferrous materials due to that; it has not yet been commercialized. Intensive research work has been carried out on surface modification of engineering components by various research groups [4-12]. It has been shown that cyaniding [13], carbonitriding [14], nitriding [4], and nitrocarburizing improve the wear resistance of steels [15]. The process used in cyaniding, nitriding and carbonitriding is a thermochemical treatment that involves diffusion of nitrogen and or carbon into the surface of the part. Diffusion of carbon and or nitrogen form nitride or carbide with substrate material to enhance its surface hardness and wear resistance. Conventional cyaniding is carried out at 800–960oC in a salt bath and involves the diffusion of C and N atoms into the steel, giving a thin wear resistant layer of the carbonitride ∈ -phase [16]. Instead of using poisonous salt cyanate, cyanide content present in the cassava plant has been utilized in several research works such as cyanidation of gold [17] and recently for PC of mild steel.