Fabrecation Of Ni-B-Si Alloy Powders And Their Sintering Properties

Nickel-based super-alloys occupy particularly important position in the whole field of high temperature alloy,and are widely used in the hottest end of various industrial gas turbine components,especially the engine blades.The reliability of super-alloy components is particularly prominent because of the poor working conditions.In order to effectively improve the working reliability and economy of aircraft engine,aircraft engine blades repairing technology has brought the attention.Powder metallurgy repairing of blades has been widely used in powder generation equipment manufacturing companies such as GE,Siemens,Westinghouse.The experiments mainly studied the influence of mechanical alloying process parameters,alloy elements and alloy content on the morphology,average particle size,micro-structure,initial melting temperature of MA powder particle.Vacuum sintering of nickel powder,nickel plate and alloy powder which was got under the optimum technological parameters vacuum sintering,then explore the impact of process parameters on the sintered micro-structure and properties at the interface,and make the foundation for the subsequent repair connection nickel-base super-alloy.Through the analysis of experiments,the conclusions are as follows:In the mechanical alloying process,the initial milled powder particle morphology of dendritic origin into overlapping lamellar surface.With the extension of milling time,the sub-stitutional solid solution formed between nickel and silicon,nickel and boron is formed between the interstitial solid solution,which make the alloy powder diffraction peak shifted and the average particle diameter refined,simultaneously the powder tends to a spherical particle morphology.Continue to increase the ball milling time,particle size leveled off,when the milling time was extended to 60h,the average particle size refined to 1?m,due to the specific surface energy increases rapidly,the powder particles gradually agglomeration,prone to amorphous transformation.The powder grain size refinement and lattice defects within the particles of the powder caused by external force in milling process are formed,which reduced atomic motion,transition resistance,so that the activation energy decreases.The continuous solid solution of boron and silicate alloying elements all reduce the phase transition temperature.With the extension of milling time,and the increasing content of alloying elements,the initial melting temperature decreased obviously.the phase transition temperature of the post-milled powder particles stabilized.Wherein the composition is 92%Ni-4%B-4%Si alloy powder in the planetary ball mill after milling 30h,the melting temperature was lowered to its 1038?.The alloy powder,nickel powder and nickel plate are conducted vacuum sintering,the experimental results show that with the increase of sintering temperature,the content of Ni₃B generated the eutectic reaction gradually decreased.The sintered organization densities,and the nickel powder is uniformly in the organization,when the sintering temperature is 1100? and the holding time extended to 120min,so that the modulus of elasticity is also stabilized.Diffuse distribution of hard phase Ni₃B strengthen the matrix,the connection strength at the interface can up to 2.189GPa,compared with the strength of the matrix(2.241GPa).When the sintering temperature up to 1200?,NiSi phase disappeared completely,while nickel substrate appears dendrite growth;continue to improve the sintering temperature,cracks appeared at the interface.