The Effect Of Mould Types And Wall Thickness On The Microstructure And Properties Of K4169 Alloy

Ni-based superalloy K4169 was studied as the research subject in this paper. The step plate castings with different mould types and various thickness were casted by vacuum melting. The solution and aging heat treatments of 1095℃for 1h+air coolingâ†'955℃for 1h+air coolingâ†'720℃for 8h+furnace coolingâ†'620℃for 8h+air cooling were conducted orderly. The effect of mould types and casting thickness on grain size and secondary arm spacing of K4169 was investigated via optical microscopy. The effect of mould types and casting thickness on precipitated phase and composition segregation was analyzed through observing the morphologies, quantity, distribution and composition of the precipitated phase acquired by scanning electron microscope. The influence of mould types and casting thickness on mechanical properties of K4169 was researched by tensile test.In the condition of the same mould type, with the decreasing of the wall thickness, the as-cast grain size and secondary arm spacing decrease and the amount of precipitated phase between the dendrites also reduces. After the heat treatment, the grain growth and secondary arm spacing growth both occur. The degree of grain growth and secondary arm spacing growth gradually increase with the augment of wall thickness. With the decreasing of wall thickness castings, the ultimate tensile strength and yield strength in room temperature are gradually raised. The maximum of tensile strength is 787MPa and there is little difference in plasticity. After the heat treatment, the room temperature tensile strength and yield strength are improved and plasticity decreases with the decrescence of wall thickness, but the tensile property in high temperature decrease apparently in comparison with that in room temperature. The properties of castings with thin wall thickness decrease markedly.In the condition of the same wall thickness, the amount of precipitated phase between dendrites in the metal casting alloy is less than that in the sand casting alloy. The as-cast grain size and secondary arm spacing in the metal casting alloy are smaller than those in the sand casting alloy. After the heat treatment, the increment of grain growth and secondary arm spacing growth in the metal castings are bigger than those in the sand castings. But the quantity of is relatively less. The tensile strength of metal castings is higher than that of sand castings. After heat treatment, the properties of metal castings at room temperature is better than that of sand castings. And high temperature circumstance has greater effect on the properties of metal castings.