Surface engineering technology used in industry for surface Essay

Surface engineering technology used in industry for surface modification( i.e surface treatment-surface thermo-chemical tratment - Essay Example This has been made feasible because steel is strong, flexible, and durable, thus, making it a suitable material for construction. However, there are instances where some modifications have to be made to the metal to make it suitable for some types of construction. The resolve to have steel that is strong, tough, wear, and shock resistant leads engineers to manipulate the surface of the metal, leaving its inner core intact (Davis, 2003). This process is called surface hardening of steel, and it can be done in many ways. Surface hardening techniques can be grouped into two main categories; local thermal treatment and thermochemical processes. The choice of treatment to be used depends on engineering requirement s as well as commercial competition. In this section, this article presents an overview of the procedures used to harden the surface of steel. Each describes the procedures involved in the two categories. 1.1 Thermo-Chemical Processes Engineers modify the local chemical composit ion of steel at the surfaces by induction of nitrogen, carbon or both. Sometimes they may also use boron. The techniques used in this category depend on the method of heat treatment applied and can further be broken down into four subcategories: i. Pack processes such as metalizing and pack carburizing ii. Salt-bath processes such as carbonitriding (cyanide hardening) iii. Gaseous processes such as gas nitriding and gas carburizing iv. Vacuum based processes including ion nitriding, carburizing, and plasma nitriding The most salient features of these processes are the processing temperature, mechanical properties and depth of the case, as well as the service behavior of the case’s core composite. Temperature is particularly significant because it affects the level of distortion directly. 1.1.1 Nitriding This can only be done on materials that have already been hardened and tempered. It produces better results when used with a range of alloys of steel that form stable nitrides such as vanadium, aluminium, tungsten, chromium, and molybdenum. The resultant nitrides are dispersed evenly throughout the surface of steel. Figure 1: Schematic diagram of a nitriding process. The process occurs at around 540 degrees Celsius where distortion does not take place. The nitride layer on the surface of the metal makes it expand, thus creating large, compressive stresses that in turn increase surface hardness and improve fatigue strength. In addition, the process also results in steel that has a reduced friction coefficient. Nitriding is, therefore, the best method to use when developing surfaces that are intended to minimize friction such as crank shafts and ball bearings. Advantages of Nitriding 1. It is easy to control the nitrogen