Effects Of Alloy Elements On The Microstrucutre And Properties Of Aluminum Bronze Coatings Fabricated By Laser Cladding

As the key units of roller hearth heat treatment furnace,the surface performance of annealing furnace roll plays a key role in the surface quality of steel plate after heat treatment and the service life of heat treatment furnace.Under the harsh service environment of a high temperature,the surface of annealing furnace roll is prone to nodulation,cracking and occurring other failure forms,resulting in the decline of product surface quality,prolonging production time and increasing production costs.This subject uses laser cladding technology to strengthen the surface of annealing furnace roll.The service life of annealing furnace roll can be prolonged and the cost also can be reduced.In this paper,aluminum bronze alloy powder with two different compositions were selected as laser cladding materials.The effects of alloy elements on the microstructure,high temperature resistance and thermal shock performance.Firstly,the effects of laser parameters on the wear and friction properties of modified aluminum bronze are considered to optimize the laser parameters which are used to fabricate the aluminum bronze.The cladding layers prepared under five different laser energy densities have good formability.Five coatings contain same phases,which areα-Cu,β′andκ.When the laser energy density decrease,the content ofα-Cu andκdecrease,the content ofβ′increase.And with the decrease of laser energy density,the microstructure of the coating become finer first and after become coarsen,which have effects on hardness and friction and wear properties of cladding layer.When the laser energy density is 42.4 J/mm²,the hardness of the cladding layer has the maximum value,up to 341.72 HV,and the wear rate reach a minimum value is4.37(10^-2mm³/N?m).It is concluded that the laser power density of 42.4 J/mm² is the best process parameter for the preparation of modified aluminum bronze cladding layer.The influence of the addition of alloy elements on the microstructure,high temperature oxidation resistance and thermal shock resistance are analyzed.It can be found from the XRD results that the addition of Fe and Ni inhibits the formation ofγ₂.Meanwhile the formation of the enhancementκphase are improved.The results of EBSD show that the addition of Fe and Ni refine the microstructure of aluminum bronze,i.e.,the grain size of modified aluminum bronze is decreased.The experimental results of high temperature oxidation test illustrate that the addition of Fe and Ni improve the high-temperature oxidation resistance of aluminum bronze.The oxidation rate constant of cladding layer is reduced from 0.11078 of pure aluminum bronze to 0.0876 of modified aluminum bronze.Meanwhile the thermal shock resistance of modified aluminum bronze is also improved.The number of cracks in the modified aluminum bronze laser cladding layer after 100 times thermal shock tests is less than that in pure aluminum bronze.