Study On The Influence Law And Mechanism Of Crystal Phase Structure On Micro-wear Of Single Crystal Alloy DD6

Single crystal nickel-based superalloy DD6 has a wide range of applications in aerospace hot-end components due to its excellent high temperature resistance and fatigue resistance.Its material damage behavior will directly affect the reliability of the engine,and fatigue wear is one of the main reasons for material failure.Its complex multi-element combination and crystal phase structure show great differences in its properties at different scales,So it is urgent to carry out research on the fatigue and wear laws and mechanisms of nickel-based single crystal alloys at the micro-scale.This article focuses on the study of DD6 wear laws and mechanisms from the microscopic scale.The main research contents and innovations of this paper are summarized as follows:(1)The two microscopic wear forms derived from the nickel-based single crystal superalloy DD6 is summarized.By comparing the microscopic wear results of different loads and cycles in the DD6 crystal phase,it is found that the DD6 crystal phase wear can be divided into two types according to the different failure modes.Under the action of large load,the wear behaviour at the crystal phase of DD6 is mainly manifested as the material removal under the mechanical leading action,and the groove structure is produced;when the wear experiment is carried out with low load and large number of cycles,it form a protruding structure.(2)The influence of DD6 crystal anisotropy and working condition on microscopic wear is studied.With a larger number of cycles,the protrusion structure at the DD6 crystal phase increases first and then decreases with the increase in load,and finally a groove structure is formed.Under the action of a small load,the volume of the protrusion structure at the DD6 crystal phase increase with the increase of the number of cycles.when the number of cycles reaches the critical number of cycles,groove wear will be produced on the protrusion structure;the change of the needle tip sliding speed in the low speed range has a greater impact on the protrusion structure;the critical contact stress for the transformation of the protrusion and groove structure is calculated through the Hertz contact model.Finally,the relationship between the critical wear load and DD6 and the sliding angle of the tip was determined.(3)The mechanism of the protrusion structure originating from the microscopic crystal phase of DD6 is proposed.In the same working conditions,the protrusion structure of the ? phase is higher than the protrusion structure of the ?' phase,and the groove structure of the ? phase is deeper than the groove structure of the ?' phase.After measurement,it is found that the reason is that the elastic modulus of ? phase is smaller,and the actual action area is larger.it is speculated that the production of the protrusion structure is related to the structural change inside the crystal.Experiments under different atmospheres prove that the protrusion structure of DD6 material is not greatly affected by oxidation and tribochemical reactions.Further combining with the results of natural aging treatment and heat treatment of the existing protrusion structure,it can be inferred that the generation mechanism of the protrusion structure is the amorphization and phase change inside the crystalline material under the action of stress,which leads to the volume expansion of the base material,and finally produces the protrusion structure.