Evaluating the Microstructural, Mechanical, and Electrochemical Behavior of Spark Plasma-Assisted Dissimilar Joining of 17-4 PH Stainless Steel to Inconel 718

In this study, the spark plasma sintering (SPS) technique was used to join 17-4 martensitic precipitation hardened stainless steel (17-4PH SS) with Inconel 718, a nickel-based superalloy (IN 718). Spark plasma assisted diffusion bonding was done at a temperature of 850 degrees C with a bonding time of 5 min under the pressure of 50 MPa. Ansys simulation was used to examine the temperature distribution and displacement during joule heating, and it was then compared to the experimental data that had been gathered. With the help of a field emission scanning electron microscope, a white conduit at the bonded zone is evident for the diffusion of elements. Electron backscatter diffraction analysis reveals the random and elongated grains, free from local residual plastic strain at the diffusion zone. Electron probe micro-analysis was used to point out the elemental diffusion among dissimilar alloys. It is observed that the elements from IN 718 are diffused to 17-4 PH SS. At the diffusion zone, there is an increment in hardness of 345 +/- 10 Hv due to the diffusion of Ni and other elements. The SPS diffusion-bonded samples have an ultimate strength of 708 +/- 5 MPa with an elongation of 9 +/- 2%. Dissolution of precipitates and M23C6 during diffusion bonding and segregation of Nb; Ti-rich carbide deteriorate the hardness and tensile properties of the bond zone which leads to a strain-free brittle fracture. An electrochemical polarization and impedance study was done in a 3.5% NaCl solution. After SPS diffusion bonding, 17-4 PH has lower corrosion resistance when compared to other regions.

Automated summary

In this study, the spark plasma sintering technique was used to join 17-4 martensitic precipitation hardened stainless steel with Inconel 718. The results showed that the diffusion of elements affected the hardness and tensile strength, and the presence of precipitates and carbides deteriorated the hardness and tensile properties of the bond zone. In addition, electrochemical testing revealed a slight decrease in the corrosion resistance of the 17-4 stainless steel after diffusion bonding.