**Abstract**

Explosive welding is a solid-state process, which is an advanced form of joining two metal plates with dissimilar metallurgical properties, irrespective of the differences in physical and chemical properties. In this process, high pressure of explosive is used to accelerate one metal plate over another to form the bimetallic product. The pressure needs to be sufficiently high and for enough length of time to achieve inter-atomic bonds. During the explosive welding process, a jetting phenomenon occurs at the collision point which cleans the top oxide layer over metals and leaves the virgin surfaces that help in the joining process. The metals are joined without losing their pre-bonded properties with higher bond strengths than the strength of the weaker parent material. There are various critical factors such as explosive type, mass of explosive, stand-off distance, type of plate material, velocity of detonation etc. which affect the bond quality. Researchers mainly play with all these parameters to bring out the best characteristics of the bimetallic product that can be used for the desired applications such as heat exchanger, pressure vessels etc.

**Keywords:** bond strength, dissimilar materials, detonation velocity, explosive welding, metallurgical properties

### **1. Introduction**

Welding is a process of joining two materials together through pressure, heat and sometimes with the addition of filler materials. The important condition for any welding technique is that the two surfaces that need to be joined should be cleaned and uncontaminated. Moreover, if the two surfaces are brought together in such a way that the surfaces exchange the outer orbit of the valence electrons and form interatomic bonds, the weld formed will be very strong in terms of mechanical properties. But this kind of bond formation is not possible through conventional means. In most of the welding techniques melting is involved in joining the two components. There are also some welding processes such as solid-state welding processes where heat required is below the melting point of the base material being welded and therefore, no melting is observed during joining for example ultrasonic welding [1, 2], friction welding [3–5], cold welding [6], explosive welding [7–10] and diffusion welding [11, 12]. All of the welding methods have some advantages and disadvantages in their particular field and are applied as per the need of the

applications. In the current world, there is an increasing trend of using dissimilar material combinations for various applications such as automobile, shipbuilding, military, aerospace and oil industries etc. The bi-metallic product takes the mechanical advantage of both the materials such as wear resistance, corrosion resistance, high tensile strength and lightweight. To meet such requirements many researchers are extensively working in this field to produce such combinations. In which explosive welding is considered as one of the potential welding technique and is gaining more attention due to its vast features as mentioned [13, 14]. Explosive welding is one of the solid-state welding processes in which explosive energy is used to create a high-velocity impact collision between the two plates to be joined. The process can join a wide area of non-compatible material combination irrespective of the difference in mechanical and chemical properties and which cannot be joined by any other conventional means. It is a surface bond welding, which provides a strong metallurgical bond at the molecular level and provides strength higher than the base materials [15]. There are various applications of explosive welding products such as in cryogenic pressure vessels [16], scram jet engine components [17], shipbuilding application [18].
