| Valves,roll and other parts working in the environment of high temperature and highpressure for a long time,which wear is serious,how to further improve the wear resistance of these parts or to repair the worn parts is an urgent problem to be solved in production.with the help of plasma arc surfacing technology,the nickel-base alloy self fluxing powder are welding on the surface of part,which can reduce the wear of the parts significantly.Plasma arc surfacing nickel-base alloy,with high hardness and low thermal conductivity,is belonging to difficult-to-machine material.Compared with the widely used grinding process at present,the cutting process is more efficient,economical and environmentally friendly.Therefore,PCBN tools were used for the hard cutting of plasma arc surfacing nickel-base alloy in this paper,the effects of cutting parameters and corner radius on cutting force,surface roughness and tool flank wear were studied,the wear behavior and wear mechanism of the tool under different cutting conditions were explored,and the influence of cutting conditions on tool wear was investigated.Firstly,the cutting force was acquired by cutting force collecting system,and the effects of cutting parameters and corner radius on cutting force were studied: cutting force increases with the increase of cutting depth,but out of proportion;With the increase of cutting speed,the cutting force shows a large downward trend;The variation rule of cutting force with feed rate and corner radius is consistent with the traditional cutting theory.The back cutting force is about two times of the main cutting force,and the unit cutting force of plasma arc surfacing nickel-base alloy is 2~4 times of the hardened steel.The influence degree of cutting depth on cutting force is biggest,followed by the cutting speed,feed rate and corner radius.Secondly,using a portable roughness meter the surface roughness was collected,and the effect of various factors on surface roughness were obtained: surface roughness increases with the increase of feed and corner radius;with the increase of cutting speed,surface roughness decreases first and then increases;and the relationship between surface roughness and cutting depth is more complex.The degree of influence of cutting depth on surface roughness is biggest,followed by feed and corner radius,the influence of cutting speed is minimal.The surface roughness obtained by turning is less than 1.3μm,and the surface quality is good,which supported the process of turning instead of grinding.Thirdly,the flank wear of tool was observed by stereomicroscope and the influence of various factors on tool wear was acquired: with increase of cutting depth and the reduce of corner radius,the flank wear of tool increases;with the increase of cutting speed,flank wear decreases first and then increases;with the increase of feed,however,flank wear decreases.The degree of influence of cutting depth on surface roughness is biggest,followed by feed,corner radius and cutting speed.The wear morphology at medium and low speed is mainly flank wear and a slight chipping occurred on the edge of blade,the main wear mechanism of tool are mechanical wear and adhesive wear.In low speed,tool flank wear mainly occurred,and have serious bonding,wear area edge chipping tool,the main wear mechanism is mechanical wear and adhesion wear;at high speed,the main wear morphology of tool is crater wear and the main wear wear mechanism are oxidation wear and diffusion wear,phase transition wear.Finally,the influence of cutting condition on tool wear at different speed was compared :wet and semi dry cutting can effectively reduce tool wear,and the effect is more significant at high speed;Compared with wet cutting,semi dry cutting can not only be comparable to wet cutting in reducing wear at high speed,but also more environmentally friendly,therefore it is worthy of further study. |
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