Study On Microstructure And Properties Of Laser Additive Gun Drill Blank Composite

The precision gun drill for processing deep hole is divided into drill shank,drill pipe and drill bit.At present,the split welding method is used for manufacturing,but there are many problems such as long manufacturing cycle,unstable performance of gun drill,poor single-side welding and double-side forming.Increase material manufacturing technology is a high-end equipment manufacturing industry in the 21st century and one of the core technology in the field of new materials,this paper adopts laser rapid integration of composite material manufacturing process synthesis of gun drill blank,can reduce the manufacturing cost,saving metal resources,research work will provide efficient high-quality eventually increase material manufacturing technology foundation,gun drill Finally realize the rapid integration of the long life gun drill laser additive manufacturing.In this paper,45 steel is used as the base material to manufacture drill pipe and drill blank successively,and VC and WC are added to improve the comprehensive performance of gun drill.H13 alloy powder was used as the laser additive manufacturing material and VC as the reinforcing phase.Stellite12alloy powder was used as the laser additive manufacturing material and WC as the reinforcing phase.The laser additive manufacturing layer of H13 alloy with2%,5%and 10%VC content was prepared on the surface of 45 steel substrate by using semiconductor laser and synchronous powder feeding laser additive manufacturing equipment,and then the laser additive manufacturing layer of Stellite12 alloy with 10%,20%and 30%WC content was prepared.Experimental study on laser additive manufacturing technology of H13 alloy powder and Stellite12 alloy powder was carried out,and the effects of VC and WC addition amount on microstructure and properties of H13 alloy laser additive manufacturing layer and Stellite12 alloy laser additive manufacturing layer were discussed.The microstructure and phase composition of laser additive manufacturing layer were characterized by OM,SEM,EDS and XRD.The microhardness,friction and wear and electrochemical corrosion of laser additive manufacturing layer were tested and analyzed.The results show that the optimal parameters of laser additive manufacturing layer for H13 alloy are as follows:laser power 600W,scanning speed 8mm·s^-1,powder feeding capacity 6g·min^-1.The optimized additive manufacturing process parameters of Stellite12 alloy laser additive manufacturing layer are as follows:laser power 750W,scanning speed 6mm·s^-1,powder feeding capacity 4g·min^-1.Other constant parameters are:shielding gas flow 15L/min,lap rate 50%,focal length 12mm.The microstructure of the laser additive manufacturing layer of H13 alloy is mainly composed of dendrites,cellular crystals and equiaxed crystals.When the amount of VC is 10%,the microstructure morphology of the laser additive manufacturing layer changes obviously compared with other layers,and the conventional dendrite morphology disappears completely,and granular precipitates appear.Not add VC layer laser gain material manufacturing phase is mainly composed of martensite,residual austenite and the composition of M₂₃C₆,along with the increase in content of VC particles,diffraction peak of phase of VC and M₂₃C₆ gradually strengthened,because the original ultrafine VC produced after hard phase decomposition V and C elements,in the subsequent chemical metallurgy reaction,precipitation of VC particles and M₂₃C₆ again.The microstructure of Stellite12 alloy laser additive manufacturing layer is mainly composed of coarse dendrites and fine cellular crystals.The addition of WC refines the grain size.When the addition amount is 30%,the microstructure is mainly composed of a small number of cellular crystals and fine dendritic crystals.The phases of laser additive manufacturing layer of Stellite12 alloy are mainly composed ofα-Co,M₂₃C₆ and Cr₇C₃,and CCo₂W₄ and W₂C phases are added when the addition amount is 10%WC.When the WC addition amount is20%,WC phase increases in the laser additive manufacturing layer,and unmelted WC particles appear.With the increase of VC and WC supplemental levels,the microhardness and wear resistance of the laser additive manufacturing layer of drill rod and drill bit are gradually improved,and the average microhardness of H13-10%VC reaches 740.41HV_0.3,1.47 times of that without VC addition.The average microhardness of Stellite12-30%WC is 1340.66HV_0.1,1.73 times that of no WC added.With the increase of VC supplemental level,the wear mechanism changes from adhesive wear to abrasive wear and oxidation wear,furrow becomes shallow,the wear amount decreases,and the wear resistance of 10%VC is the best.The wear mechanism of Stellite12 laser additive manufacturing layer is mainly abrasive wear and adhesive wear,and the wear resistance is small.With the increase of WC addition amount,the wear mechanism changes from abrasive wear and adhesive wear to oxidation wear.The furrow becomes shallower,the oxide scale increases,and the wear rate is slowed down.The wear resistance of 30%WC is the best.With the increase of WC addition amount,the corrosion rate of laser additive manufacturing layer decreases firstly and then increases.The addition amount of 20%WC has the worst corrosion resistance.Due to the existence of WC particles,cracks and other defects are easy to produce small hole corrosion and gap corrosion.The addition of 10%and 30%WC has better corrosion resistance.The influence of VC and WC addition amount on forming quality,structure and performance of drill pipe and drill bit blank laser additive manufacturing layer was comprehensively analyzed.In this paper,VC was used to add 10%in drill pipe blank laser additive manufacturing layer,and WC was used to add 30%in drill bit laser additive manufacturing layer.