![]() Three austenitic base metals were studied: Type 310 stainless steel, Ni-based Alloy 690, and super-austenitic Alloy AL-6XN. The test is robust and allows for changes in the testing parameters and material condition to develop a fundamental understanding of factors that affect cracking. Threshold strain for fracture (ε min) and the ductility dip temperature range (DTR) can then be extracted from these envelopes and used to compare susceptibility among materials. Samples are tested over a range of temperature and strains, producing temperature-strain cracking envelopes. The strain-to-fracture (STF) test has been developed to determine susceptibility to ductility dip cracking (DDC) and other elevated-temperatures cracking phenomena. ![]() CRACKED WROBOT CRACKIn addition to a ranking of materials and processes, interim results regarding the crack types and the metallurgical causes of cracking are discussed. In order to gain further knowledge regarding formation and propagation of the hot cracks, optical microscopy and EDX-analyses were performed. Hot cracking tests are performed by PVR test (deformation crack test), using GTA-welded externally loaded specimens to rank the hot cracking sensitivity of the base metals. This paper presents a comparative overview of the hot cracking susceptibility of iron and nickel-based alloys type 1.4958 (alloy 800 H), 2.4663 Q (alloy 617), 2.4816 (alloy 600 H), 2.4856 (alloy 625) and 2.4605 (alloy 59). Their outstanding corrosion performance, however, is often accompanied by a limited weldability due to a high hot cracking sensitivity. Future research directions aiming at the reason of abnormal fracture mode, the effect of the state of applied stress, the influence of strain rate, and the development of the theory nonequilibrium grain boundary segregation, are suggested to provide a complete understanding of intermediate temperature embrittlement.ĭue to their good corrosion resistance in high-temperature and wet corrosive environments, nickel-based alloys are widely used as construction materials in the chemical industry, as well as in offshore applications and other energy and environmental technologies. ![]() It is shown that the mechanism of intermediate temperature embrittlement has not been satisfactorily explained yet and “nonequilibrium interface segregation” of impurities taking into account the effect of strain rate may be the origin of intermediate temperature embrittlement of Ni and Ni-based superalloys. Based on the generality, these interpretations are discussed through the representative investigations on intermediate temperature embrittlement. The existing interpretations of the mechanism are then outlined. To clarify this situation, the present article first confirms the generality of intermediate temperature embrittlement of Ni and Ni-based alloys by the experimental results reported in the literature. A comparison of published papers by various authors reveals considerable differences in understanding the mechanism of intermediate temperature embrittlement. However, many experiments demonstrated that these alloys as well as Ni always show ductility loss at intermediate temperature, which constrains further development. Ni-based superalloys play an important role in aircraft engine propulsion. In parallel, hot tensile tests following fast heating were performed to determine the DDC temperature range, to try and correlate DDC to the thermomechanical behavior. This test clearly demonstrates the effect of multiple passes on the occurrence of DDC. ![]() This test is based on multiple welding beads on a cuboidal mockup. To do this, we designed a simple hot crack susceptibility test. This work is undertaken to determine more precisely the thermomechanical conditions of the occurrence of DDC in two types of materials: filler metals 52M and 152. However 690 alloy, and the corresponding welding filler metals (types 52 and 152), can be sensitive to a solid state hot cracking phenomenon during welding, called “ductility dip cracking” (DDC) associated to grain boundary cracking. Inconel® alloy 690 is nowadays commonly used instead of 600 for the manufacturing of certain components of the primary circuit of pressurized water reactor (PWR) nuclear power plants, due to its superior resistance to corrosion and stress corrosion cracking. ![]()
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