Microstructural Analysis of Laser Cladding of Stellite 6 on Ductile Iron

Stellite 6 alloy in the form of powder was deposited on a ductile cast iron substrate using a low power pulsed Nd:YAG laser. The effects of process parameters on the resulting microstructure and hardness were studied with emphasis on the single and multi-track deposits. The results revealed that the cladded layers consist of carbides dispersed in a Co-based solid solution matrix with a dendritic structure. Multi-track cladded layers have coarser dendrites compared to those of single-track cladded layer due to a longer exposure time at high temperature and slower cooling rates as more layers were deposite

Submerged Friction-Stir Welding (SFSW) Underwater and Under Liquid Nitrogen: An Improved Method to Join Al Alloys to Mg Alloys

Submerged friction-stir welding (SFSW) underwater and under liquid nitrogen is demonstrated as an alternative and improved method for creating fine-grained welds in dissimilar metals. Plates of AZ31 (Mg alloy) and AA5083 H34 were joined by friction-stir welding in three different environments, i.e., in air, water, and liquid nitrogen at 400 rpm and 50 mm/min. The temperature profile, microstructure, scanning electron microscopy (SEM)-energy-dispersive spectroscopy (EDS) analysis, X-ray diffraction (XRD), hardness, and tensile testing results were evaluated. In the stir zone of an air-welded specimen, formation of brittle intermetallic compounds of Al3Mg2, Al12Mg17, and Al2Mg3 contributed to cracking in the weld nugget. These phases were formed because of constitutional liquation. Friction-stir welding underwater and under liquid nitrogen significantly suppresses the formation of intermetallic compounds because of the lower peak temperature. Furthermore, the temperature profiles plotted during this investigation indicate that the largest amount of a dagger T is generated by the weld under liquid nitrogen, which is performed at the lowest temperature. It is shown that in low-temperature FSW, the flow stress is higher, plastic contribution increases, and so adiabatic heating, a result of high strain and high strain-rate deformation, drives the recrystallization process beside frictional heat

Laser welding of niobium to 410 steel with a nickel interlayer produced by electro spark deposition

Some combination of metals such as niobium to stainless steel cannot be joined directly by laser welding due to formation of deleterious phases. On the other hand placement of a narrow strip of a third alloy between the two metals can introduce many technical and availability limitations. In this work, a more versatile method is developed using electrospark deposition (ESD) for facilitation of subsequent Nb to 410 stainless steel dissimilar laser with minimum heat input successfully. The 1 mm Nb plate edge was clad by Alloy 82 using a 4 mm round electrode by ESD process. The layer has minimum dilution with Nb while having a metallurgical bond. It exhibited a fine cellular structure with Laves phase particles with 30–50 nm in diameter. The Nb plate with edge built up was then laser welded to 410 stainless steel using a 1 KW fiber laser machine. The presence of the interlayer material suppressed the formation of Nbsingle bondFe intermetallic in the laser fusion zone and increases weldability. Tensile test of dissimilar laser weld with the nickel base ESD interlayer exhibited an ultimate strength of 285 MPa with the failure located at the Nb side and not in laser weld metal or at the ESD interface

Characteristics of electrospark deposition of a nickel-based alloy on 410 stainless steel for purpose of facilitating dissimilar metal welding by laser

In this research, a new method is developed using the electrospark deposition (ESD) process for making an interlayer, which could be useful in welding dissimilar metals. Alloy 82 nickel-based alloy was deposited on the edge of a 410-stainless-steel plate and used as an interlayer for subsequent welding to a nickel Alloy 82 plate forming a dissimilar metal weld. Metallographic analysis showed that the ESD layer consisted of a γ phase, columnar grains oriented in {100} direction and cellular solidification morphology with 250–350 nm cell diameter. Neither Lave phase nor large carbide crystals were observed in the microstructure of ESD layer due to the high-cooling rate and the low tendency for segregation. Tensile test exhibited an ultimate strength in excess of 420 MPa, and failure of the joint occurred in the 410 stainless steel base metal indicating good weldability of the ESD interlayer to the base metal

The effect of electrospark nickel interlayer thickness on the characteristics of Niobium to 410 stainless steel dissimilar laser welding

Dissimilar welding of Niobium to 410 stainless steel has important engineering applications. An interlayer should be used for avoiding or reducing formation of brittle intermetallic phases in weld. In this research the effect of gradual addition of ESD interlayer on the chemical composition, microstructure and mechanical properties of Nb to 410 stainless steel dissimilar laser welding is investigated. The Nb plate with the ESD interlayer thickness equivalent to about 25%, 50%, and 100% of base plate thicknesses on its edge (produced by novel electrospark deposition process) was laser welded to 410 stainless steel by pulsed Nd:YAG laser. The welds were then subjected to metallographic, X-ray diffraction and mechanical tests. Results showed that with an increase in ESD interlayer thickness, the weldability increased due to reduction of brittle μ and ε-Laves intermetallic phases in the fusion zone. Tensile test results of dissimilar Nb to 410 stainless steel weld, showed that the chemical composition of the dissimilar weld zone determines the mechanical strength of the joint. Furthermore, in order to reach high mechanical strengths, contact of the weld pool and its solidification on the Nb also has to be avoided due to formation of brittle ε-Laves phase