Filler metal

About: Filler metal is a research topic. Over the lifetime, 11152 publications have been published within this topic receiving 86590 citations.

Comparative Study of Friction Stir Welding and Tungsten Inert Gas Welding Process

Abstract: An experimental investigation has been carried out on microstructure, micro hardness distribution, tensile properties and fracture surface morphology of weld butt joints of 6061 T6 aluminum alloy. Two different welding processes have been considered: a conventional tungsten inert gas (TIG) process and an innovative solid state welding process known as friction stir welding (FSW) process. Micro hardness distribution results showed a general decay of mechanical properties of TIG joints, mainly due to high temperature experienced by the material. Instead, in FSW joint, lower temperatures are involved in the process due to severe plastic deformation induced by the tool motion and lower decay of mechanical properties. In the nugget zone a slight recovery of hardness is observed due to recrystallisation of very fine grain structure. Hence from industrial perspectives, FSW process is very competitive as it saves energy, has higher tensile strength and prevents the joints from fusion related defects.

Unmixed zone formation in austenitic stainless steel weldments. [18 Cr-8 Ni weldments]

Abstract: An investigation of the weld interface region in heterogeneous austenitic stainless steel weldments on an 18Cr-8Ni base metal indicates that a well-developed unmixed zone exists along the boundary separating the weld composite region from the partially-melted region. Since the unmixed zone exists as a laminar layer of base metal which has melted and resolidified in situ during the welding process, the average composition of this region is identical to that of the base metal. The duplex austenite-ferrite microstructure of the unmixed zone appears similar morphologically to the microstructure of autogenous 18Cr-8Ni weldments. Constant extension rate stress-corrosion cracking tests were performed on transverse-welded tensile specimens in room and elevated temperature chloride-containing solutions which readily produce stress-corrosion cracking in 18Cr-8Ni base materials. Test results indicate that the duplex unmixed zone can be preferentially susceptible to corrosion-induced attack. Preferential environmentally-induced cracking in the unmixed zone of both Type 310/Type 304L and Type 312/Type 304L weldments is particularly severe in low pH, room temperature solutions; it involves the combined and interrelated occurrence of stress-assisted ferrite dissolution and stress-corrosion cracking in the austenite. Designing a wholly austenitic weldment by simply using a high-nickel filler metal is not possible. It could lead to catastrophic results ifmore » such weldments are employed under conditions conducive to stress-corrosion cracking.« less

Study on hybrid heat source overlap welding of magnesium alloy AZ31B

Abstract: The magnesium alloy AZ31B was overlap welded by hybrid welding (laser-tungsten inert gas arc). According to the hybrid welding interaction principle, a new heat source model, hybrid welding heat source model, was developed with finite element analysis. At the same time, using a high-temperature metallographical microscope, the macro-appearance and microstructure characteristics of the joint after hybrid overlap welding were studied. The results indicate that the hybrid welding was superior to the single tungsten inert gas welding or laser welding on the aspects of improving the utilized efficiency of the arc and enhancing the absorptivity of materials to laser energy. Due to the energy characteristics of hybrid overlap welding the macro-appearance of the joint was cup-shaped, the top weld showed the hybrid welding microstructure, while, the lower weld showed the typical laser welding microstructure.

Strength and Microstructure of Silicon Nitride Ceramics Brazed with Nickel‐Chromium‐Silicon Alloys

Abstract: Joining of sintered Si{sub 3}N{sub 4} was performed using a high-temperature brazing technique. Ni-based brazing alloys having the same Ni:Cr ratio as AWS BNi-5 (Ni{center_dot}18Cr{center_dot}19Si (at.%)) but different Si content were used as the brazing filler metals. Joining experiments were performed at 1,220 C under a N{sub 2} partial pressure of 15 Pa for different times between 5 to 15 min. The highest room-temperature four-point bend strength of the joints was 115 MPa, whereas 220 MPa was achieved when the joints were tested at 900 C. The high strength of the experimental joints was attributed to the reduction in residual stresses and formation of a CrN reaction layer at the ceramic/filler metal interface.