Experimental Research On Cutting Performance Of Cobalt-base Alloy By Surfacing And Tool Wear

Surfacing cobalt-base superalloy is characterized by a strong resistance against wear,high temperature and corrosion,thus be wide applications for workpieces with special requirements of surface quality.However,this does not mean that surfacing cobalt-base superalloy has no defects.The high hardness,uneven organization of the surfacing layer and poor thermal conductivity turn it into one of materials which are hard to process.In order to realize efficient and high-hardness cutting and processing of surfacing cobalt-base superalloy,this paper performs the cutting and processing experiment to study the reasonable tool materials and scope of cutting parameters for different processes of rough machining and finish machining.Meanwhile,revolving around finish machining,the rules of the influence of cutting parameters on the cutting force,degree of surface roughness,and wear loss of the flank surface of cutting tools are studied.Also,the wear process,wear form and wear mechanism are examined.First of all,the mono-factor analysis is performed to study the reasonable tool materials and cutting parameter scope for different processes of rough and finish machining.Results show that,during the process of rough machining,hard alloy cutting tools with a favorable toughness and impact resistance should be adopted.At certain cutting speed and back engagement of the cutting edge,it is more reasonable to reduce the circular arc radius of tool edge and feed;on the contrary,cubic boron nitride(CBN)tools with a high hardness and resistance towards high temperature should be adopted,which demonstrate a favorable cutting performance at a fast cutting speed.Following that,the CBN tools are employed and the orthogonal experiment is performed to study how the cutting condition and the edge circular arc radius can influence the cutting force,surface roughness and wear loss of the flank surface of cutting tools.Results indicate that,with the increase of the back engagement of the cutting edge,the surface roughness first maintains unchanged,and then changes,which increasing turns to decreasing;on the whole,the cutting force has been on the whole increasing but does not constitute a positive proportion;the wear loss of the flank surface of cutting tools is on an upward trend.With the increase of the cutting speed,the surface roughness first decreases and then increases;the cutting force is generally on a downward trend.The wear loss of the flank surface of cutting tools first decreases and then increases.With the increase of feed,the surface roughness andthe cutting force both rise,but the increase rate of the cutting force is relatively small;the wear loss of the back engagement of the cutting edge first decreases and then increases.With the increase of edge circular arc radius,the surface roughness rises accordingly,the change rules of the cutting force coincide with the traditional cutting theories.The wear loss of the flank surface of cutting tools first increases and then decreases.At the same time,the range analysis is conducted to study the influence extent of various factors on the cutting force,surface roughness,and wear of the flank surface of cutting tools,respectively.On that basis,the model predicting the cutting force and the surface roughness is built.Finally,the wear process of CBN tools at different cutting speeds is examined,and the SEM(scanning electron microscope)and energy spectrum analysis are performed to discuss the microscopic wear appearance and wear mechanism of tools.Analysis results indicate that,at an intermediate speed and at the medium and high speed,the curve showing the wear process of the rake and flank surface of cutting tools consists of three wear periods.At a high speed,the curve of the wear process demonstrates no significant normal wear stage.At an intermediate speed,the normal wear stage of the rake face of cutting tools is longer than the normal wear stage of the flank surface of cutting tools.The wear reason of cutting tools mainly includes the mechanical wear,bonding wear,diffusion wear,oxidative wear,micro-destruction,etc.