Study On Heat Treatment Process And Mechanical Properties Of GH4169 Alloy Used As Stir Tool

GH4169 alloy is a precipitation-strengthened nickel-based superalloy with good hightemperature stability and processing properties,and is widely used in aerospace,chemical,and marine fields.Due to the good comprehensive mechanical properties,GH4169 alloy is listed as one of the main candidate materials for the stirrer head in friction stir welding,but there is currently no systematic research on this alloy combined with this special service condition,therefore,this article takes GH4169 alloy as the research object,comprehensively considered its service performance requirements,the microstructure and performance have been adjusted through different heat treatment processes;considered the over-temperature service conditions involved in this application method,the effects of short-term high-temperature aging on its mechanical properties have been studied;combined with the wear status of the application,the effects of load and temperature on its friction and wear performance have been studied,and the wear mechanism has been analyzed.These studies provide theoretical support for the practical engineering application of the candidate material GH4169 alloy.The main research results of this article are as follows:The effects of different heat treatment parameters on the microstructure and mechanical properties of GH4169 alloy have been studied.The results show that as the temperature of the solution treatment increases,the ? phase begins to dissolve,the pinning effect on the grain boundaries gradually weakens until it disappears,the grains begin to coarsen,the hardness and tensile strength of the alloy continue to decrease,and the impact toughness increases.Among them,the hardness value of GH4169 alloy after heat treatment at 1010 ? × 1 h(WC)+ 720 ? × 8 h(50 ? / h,FC)+ 620 ? × 8 h(AC)process(CST)is 43.2~44.9 HRC,and the grain size grade is 8.5.The absorbed impact energy is 106.6~109.2 J,the tensile strength is 1340~1343 MPa,the fracture is a typical dimple fracture,and the comprehensive performance is more suitable.After the heat treatment(CST),with the extension of the holding time at 900 ?,the strengthening phase dissolves,and the ? phase continuously precipitates,starting from the grain boundary and finally covering the entire crystal.The morphology changes from the initial short rods and particles to long needles,and the hardness of the alloy decreases.Precipitation of an appropriate amount of ? phase along the grain boundary can improve the tensile strength and elongation of the alloy.When a large amount of ? phase is precipitated in a needle shape,it will adversely affect the high temperature strength and high temperature plasticity of the alloy.Dry sliding friction and wear tests have been performed on the GH4169 alloy before and after heat treatment at room temperature.The wear mechanism of the alloy before heat treatment is mainly adhesive wear,and the wear mechanism of the alloy after heat treatment(CST)is mainly abrasive wear,both of which are accompanied by slight oxidative wear.The friction coefficient of the alloy after heat treatment(CST)is significantly reduced and the overall fluctuation range becomes smaller,the friction process is more stable,the wear rate is reduced from 1.56 mm3 / mm to 0.67 mm3 / mm,and the wear resistance is significantly improved.The effect of load and temperature on the friction and wear properties of GH4169 alloy after heat treatment(CST)have been studied.The results show that at room temperature,a slight-severe wear transition will occur with increasing load,the friction coefficient of the material decreases from 0.34(5 N)to 0.29(15 N)as the load increases,the wear rate increases from 0.13 mm3 / mm(5 N)to 2.01 mm3 / mm(15 N).When the load is 5 N,the wear mechanism is mainly abrasive wear,accompanied by a small amount of oxidative wear characteristics.As the load increases to 10 N and 15 N,the oxidative wear mechanism is more significant.Under the condition of constant load,a slight-severe-slight abrasion transition occurs with the increase of temperature.The small amount of oxides generated at 300 ? can not alleviate the negative effects of high temperature softening of the sample.When more dense oxide layer is formed at 500 ?,it can significantly protect the friction contact surface and reduce the wear rate.When the load is 5 N,the wear mechanism at room temperature is mainly abrasive wear,at 300 ° C and 500 ° C,oxidative wear is the main wear mechanism.