Study On Powder Metallurgy Nickel - Based Alloy For Extrusion Die Material

The extrusion die always works under the condition of high temperature, high pressur e, complex friction and periodic variable load. Then it is high demand for the performance of the die, but the general extrusion die can not meet the requirements with the low use life and the rough internal structure,which making the extrusion profiles producing defects that rough surface and crack.It is especially easy to making the extrusion die producing defects,such as crack,strain,wear damage and deformation,when the extrusion profile has complex section,thin wall and long cantilever.The nickel alloy has been widely used in many fields,especially the high temperature alloy field.the alloy has the good comprehensive performan ce,such as hardness,creep properties,oxidation resistance, fatigue resistance fracture tough ness and plasticity,under the high temperature condition.what is more, the nickel alloy has t he excellent performance of corrosion resistance under the oily condition.The high temperat ure nickel alloy will be the material of the extrusion die from the above excellent comprehe nsive performance.The alloy studied in the paper was prepared by powder metallurgy and vacuum sintering. The effect rule of different ball-milling,vacuum sintering and heat treatment parameters were studied by mechanics performance tests at room and high temperature,tensile tests at room temperature, XRD, OM, SEM, and EDS tests. The comprehensive research results are as follows.(1) when the milling time goes 48 h and the milling rotating speed goes 320r/min, with different specifications of the big and middle of balls. we can obtain the powder that owns better particle size. And the powder can be pressed directly without any forming agent.During the ball milling process, the powder can be polluted by nylon jar mill and the grinding ball material.To be controlled,the result show that using the nylon jar mill is the best choice.(2) The microstructure of the sintered Nickel base alloy is mainly composed ofγ,γ’,MC and a few harmful phase σ, γ’dispersed in the γ matrix.With the prolongation of milling time and the increase of sintering temperature, the crystal grain to be tinier,the uniform distribution of second phase becomes more uniform and the densities hardness, compressive strength of the alloy increase.When the sinteringtemperature up to1330℃,then while at 800℃, the result show that the frictional and the wear rate of the alloy are the minimum and that the hardness,compressive strength of the alloy are the best.(3)Hardness changes with the increase ofγ’ phase(first reduce then increase).The influence of solution time onγ’ and hardness is slight.Through influence the morphology and volume fraction ofγ’ phase cooling manner after solution treatment influence hardness strongly.Afterageing treatment the changes of hardness is similar with before-ageing treatment.