Microstructure Analysis of 17-4 Precipitation Hardened Stainless Steel at Welded Spots in Resistance Spot Welding

Abstract

Many researchers have developed models which are capable of analyzing the effects of process parameters on the responses of different welding operations carried out on 17-4 PH steel which bears extensive properties and have wide range of applications. The weld quality of any material plays a major role in determining the strength of the joint. Hence a proper and procedural analysis has to be made in order to assess the quality of the weld. This could happen only when the analysis of the weld quality is reviewed. Here in this work, RSW of special kind of stainless steel is welded considering the very important parameters which alter the response characteristics to a greater extent. From literature it is evident that no full proof plan is available to conduct welding process of any kind. Hence, an attempt is made to design experiments of welding on the material with the help of Taguchi method and the same is analyzed using ANOVA for the superiority of the parameters on basis of which the optimization of responses can be done. The weld quality can be assessed using one of the responses known as tensile test which determines the breaking load required for the failure of the welded specimen. The micro structural analysis is then carried out using Scanning Electron Microscope which yields the results of failure analysis. It can be clearly seen from the results that the electrode force is the most effecting factor which behaves linearly and then the weld current which drastically or nonlinearly change the characteristics of the response (tensile strength). The micro structural analysis shows that the dimple and ridges are present at the break point which is the evidence for the ductile property of the material. From the pictures of the SEM results, the even distribution of the secondary phase particles is clearly visible, this is again the evidence for the ductile property or the increase in the yield strength. Also pores and cracks are visible but up to a very smaller extent, hence more resistance of the joint for breaking when the load is applied can be seen.