The Research About Repair Welding The Foundry Defects That Delicate Casting Of Alloy K423A

Nickel-based high-temperature alloy has good corrosion resistance, high melting point, good features such as high performance.so it is the most widely used in aviation engine parts manufacturing process of high temperature resistant material.A domestic aviation enterprise with nickel based high temperature alloy K423 A as raw materials of parts in the process of casting, prone to defects such as cracks, loose,porosity.In the current casting technology under the condition of these defects are hard to avoid completely, only by the method of repair welding to repair the defective castings, but the effect is not ideal in the actual production process, when the repair welding is easy craze, percent of pass is very low.In order to meet the demand of enterprise production, must raise K423 A casting repair welding repair rate.Therefore,study of K423 A casting repair welding repair is of great significance.The current application of the welding of nickel-based superalloy welding methods mainly include electron beam welding, laser welding, brazing, argon arc welding, etc. But the test was on hand of argon arc welding(TIG welding) welding method for studying the weld, using different welding filler material and welding parameters for welding test, through X-ray nondestructive flaw detection to test the welding joint determine the best filling material and process parameters. Test by optical microscope, scanning electron microscopy and energy spectrometer, X-ray diffractometer, etc of the welded joint crack morphology, microstructure, phase structure and composition analysis, studies the forming mechanism of K423 A alloy welding hot crack. In this paper, the following is the experimental results:(1) By HGH3030, HGH625, HGH3113 three solder repair welding result analysis found that the three kinds of solder can be qualified welds welded joint, but after two better compatibility with the parent metal welding, solder welding qualified rate is quite high. Determine the appropriate welding process parameters: the welding current is 40 ~ 50 a, the welding voltage of 10 v, argon gas flow positive 8 L/min, the back 15 L/min.(2) For repair welding qualified K423 A alloy welded joint was studied to eliminate stress after welding heat treatment, the experiment adopted two kinds of heat treatment scheme, respectively is solution 1) : 1065 ℃ heat preservation 2 h, argon filling with furnace cooling, the scheme 2) : 1190 ℃ heat preservation 2 h, air coolingto 1065 ℃ heat preservation 2 h, argon filling with furnace cooling. The results show that using plan 1) heat treatment of welded joint crack of all, and adopts the scheme 2)heat treatment of welded joint is not appear crack. For heat treatment after welding of the welding joint microstructure analysis found that heat treatment followed by a large number of gamma, and carbide precipitation, carbide has the characteristics of grain boundary precipitates, this is the main cause of weld crack after heat treatment.(3) K423 A superalloy repair welding process of main liquefied crack, crack solidification crack, crack, strain aging is one of the most vulnerable to strain aging crack. Most is at the center of the weld solidification crack, there are a few in the heat affected zone and near the fusion line. And did not produce cracks in weld solidification crack area, respectively, the energy spectrum analysis, the results showed that the crack area of alloy composition and parent metal, and the crack element composition change, C, Ti, Mo, is three kinds of elements.(4) K423 A superalloy liquefied cracks appearing in the welding process was due to the low melting point eutectic composition of liquid membrane, which make organization liquefaction, when limited stress liquid membrane were cracking caused liquefied crack.Liquefied crack formation mainly related to material composition,general heat affected zone, the intergranular cracking characteristics.Crack shape of continuous and intermittent, each crack are characterized by end for coarse and dull,the other end of the fine, sharp, thin and one end of the crack tip end is more easy to extend.Through the microstructure analysis, found that the coarse grains and clear direction of the columnar crystal area more prone to crack.The crack energy spectrum analysis found that cracks in C, Ti, Nb gathered the most three elements.