Ceramics are nonmetallic, inorganic, amorphous solids and are mostly metallic oxides. They have poor tensile strength, and are brittle. They can be either crystalline or noncrystalline. Many ceramics are workable in extremely low (cryogenic) temperature range, while many others are able to sustain high temperatures. Silica, silicates, NaCI, rock salt, MgO, CaF2, glasses, CsCl etc. …
In this article I will discuss chemical heat treatment processes. These are: 1. Case Hardening Process (or carburising) solid or pack carburising liquid carburising, and gaseous carburizing. 2. Cyniding 3. Nitriding 4. Carbo-nitriding 5. Flame hardening 6. Induction hardening All other heat treatment processes are discussed in the preceding article. This article is next part …
The properties of metals and alloys can be changed by heating followed by cooling under definite conditions to make them suitable for specific applications. Accordingly steel can be hardened to resist cutting action and prevent abrasion. The rate of cooling and the manner of cooling are the controlling factors in heat treatment processes. Heat treatment …
Carbon steels (or plain carbon steels) are ferrous metals. Percentage of carbon in them varies from about 0.05% to 2%. Accordingly they are classified as mild steel, medium carbon steel and high carbon steel. Mild steel is soft, medium carbon steel is tough, and high carbon steel is hard in comparison to each other. Following …
Microstructural Changes Refer to phase diagrams of preceding article. Liquid phase first changes to solid-liquid phase, and finally to solid phase during cooling. If variation in the rate of cooling is slow to fast, say 200°C per hour to 200°C per second, different microstructures will develop. If we consider the slow rate of cooling which …
Phase diagrams are important and essential tools to understand compositional concentrations of two or more elements. These are influenced by temperature and pressure. Melting point of tungsten is 3400°C and that of aluminum 657°C, hence the two elements cannot blend together as their solid-liquid or intermediate phases restrict them to do so. However melting point …
Materials are transformed into various phases under the effects of temperature and pressure. The iron is available in BCC form (α-iron), FCC form (y-iron) and BCC form again (δ-iron) at certain temperatures. The development of alloys, whether non-ferrous brass or ferrous high speed steel (H.S.S.); magnetic alnico or antifriction babbits, require the knowledge of solid …
Definition of hardness: Hardness is a surface property. It is defined as the resistance of a material against permanent deformation of the surface in the form of scratch, cutting, indentation, or mechanical wear. Diamond is the hardest known material. In various hardness tests, the indentors are used to introduce indentation on the surface. The shape …
In order to determine the mechanical properties of materials certain tests are carried-out. Depending on the nature of tests, these are classified as follows: Non-destructive tests (NDT) in which the materials or their specimens are not broken. Destructive tests in which the specimens of materials are fractured or deformed. Destructive Tests Generally specimens are tested …
The non-destructive testing (NDT) refers to a method of detecting internal flaws in engineering materials, machine components, and structures without breaking them. These tests are essential to ascertain absolute safety and reliability in engineering applications: particularly in strategic industries such as atomic energy, missiles, defense, aeronautics, space etc. The non-destructive testing techniques can be employed …