Study On Microstructures And Properties Of P-TIG Welded Joint In Inconel601H Nickel-based Alloy

Inconel601H nickel-base superalloy is one kind of solution strengthening type. It hasexcellent mechanical properties and corrosion resistance performance in high temperature,so having been widely applied in many fields, such as petrochemical industry, aerospace,thermal energy and electric fields. In this paper, the Inconel601H nickel-base superalloyswere welded by P-TIG (pulsed tungsten argon welding). Microstructure of welded jointswas observed and mechanical properties of welded joints were tested, finally therelationships between the microstructure and properties of welded joints with weldingprocess were analysed. The findings of research were shown as following：(1)Weld macromoldings are better and there are no the appearance of welding defects when the weldingheat input ranging from5.4KJ·cm-1to6.08KJ·cm-1.(2)The microstructures of base metalare mainly austenitic phase and a small amount of the γ ’phase in the base of the γ phase;Microstructures of weld were mainly coarse austenite columnar grains, but when thewelding heat input increases to5.4KJ·cm-1, equiaxed grains appear in the center of theweld; Precipitated phases of weld are mainly γ′phase and only a few MC carbides. γ′phasestrengthened the matrix.(3)Knowing from orthogonal experiment analysis of the specimenstensile strength，peak current has the biggest effect on the specimens tensile strength in allof the weld parameters, and then welding speed at the second place. The theoretical optimalwelding parameters obtained by orthogonal experiment is that peak current is160A, thewelding speed is12cm·min-1, pulse current frequency is2Hz, the duty cycle of the pulsecurrent is30%, and the wire is ERNiCrMo-3. Knowing from the fracture morphologys,welded joints of eight sets specimens are ductile fracture， showing good toughness.Welding heat input has a significant effect on the tensile strength of welded joints.Following welding heat input increasing, the tensile strength of welded joints first increaseand then decrease. Owing to the increasing of the welding heat input, the equiaxialstructures exists in the central portion of the weld, and then improve the tensile strength ofwelded joint. However, coarse grains appear in heat affected zone, resulting in lower tensilestrength of welded joints, when the welding heat input increase to7.6KJ cm-1.（4）Thehardness of the welds has a certain improvement than the hardness of the base material,hardness of the heat affected zones has a slightly lower than the hardness of base material. With welding heat input changing, hardness distributions of the welded joints show acertain regularity: The hardness near the fusion line is harder than the center of the weld，and this change is more obvious with the increase of the welding heat input. This is due tothe formation of larger size equiaxed grains at the center of weld; When the welding heatinput increase to7.6KJ cm-1, the hardness of the heat affected zone shows obviouslydecline, resulting from coarse grains existed in the heat affected zone.