Development of explosive coating setup to deposit Ni-Al coating on Steel Substrate

Abstract

Explosives are commonly used in manufacturing processes for forming and welding operation. However, no literature is available so far on using explosive for coating application. For coating deposition by thermal spraying process, normally D-gun spraying, HVOF and plasma spraying processes are used. These are complicated and costly processes which often require skilled labor to operate the system. The objective of the present research is to develop a new technology to deposit powder materials on steel substrate by using explosives. The main focus of this research is to develop the setup with the ability to deposit coating with less production cost and high deposition efficiency. In the first segment, a low-cost explosive coating set up is developed. The technical parameters like standoff distance, distance between powders, number of ignition points, and relative quantity of powders are obtained and optimized through experimental studies by using gun powder as explosive. Further with optimized process parameters, Ni-5Al alloy powder is successfully deposited on the grit blasted steel substrate. In the second segment of this research, the explosively sprayed Ni-Al coating is characterized by various characterization techniques. The phases of the coating material and coating microstructure are studied by using XRD analysis and FESEM techniques respectively. The mechanical properties of the coating are estimated by using a scratch test, microhardness test, and reciprocating type wear test. The Ni-Al coating is found to be hard, wear resistant and well adhered to the substrate. In the last segment, deposition efficiency of coating material has been improved by using a different composition of explosive (flash powder) having higher heat content and velocity of a shock wave. The properties of both types of Ni-5Al coating deposited by two different compositions of explosive material are compared. Superior mechanical properties and higher deposition efficiency are obtained in case of Ni-5Al coating deposited by flash explosive powder.