Preparation Of WC-Ni₃Al-Si₃N₄ Composites And Laser Micro Machining Performance Study

The surface micro-texture of the cutting tool in the cutting process can reduce the cutting temperature,the cold welding,adhesion and diffusion,so it is very suitable for cutting aluminum and titanium alloy which is easy to make the tool wear and tear.However,the requirement that cutting tool with surface micro-texture towards the intensity of the texture is extremely high,therefore,we must first ensure that the substrate material of tool has sufficient high temperature hardness,strength and chemical stability,secondly,the defects of micro-texture caused in the processing should be eliminated as far as possible.WC-Co cemented carbide is the most widely used base material for the preparation of surface micro-texture tools,however,the addition of Co decreases the hardness,wear resistance,corrosion resistance and chemical stability of the cemented carbide at high temperature.Ni₃ Al intermetallic compounds with better properties were selected as the WC binder phase,and WC-Ni₃ Al composites were strengthened and strengthened by ?-Si₃N₄ whisker to further improve the comprehensive properties of the composites.Secondly,laser processing in water,liquid nitrogen and ice layer is used instead of air processing to improve the surface micro-texture processing quality.In this paper,in-situ ?-Si₃N₄ whiskers were first introduced to toughening composites,and the WC-6 wt.% Ni₃Al-4 wt.% Si₃N₄ composite was used as the research object.Using two-step SPS sintering process?1800?-0min-0MPa?1400?-10min-30MPa?,the phase transformation of ???-Si₃N₄ and phase growth of ?-Si₃N₄ can not be achieved due to the low density of the material at high temperature sintering;Using multi-step SPS sintering process?1400?-2min-30MPa?1800?-0min-0MPa?1400?-10min-30MPa?,due to the overflow of a amount of sintering liquid phase at high temperature sintering,leading to ???-Si₃N₄ transformation and phase growth lack of liquid phase conditions,so only a small part of the?-Si₃N₄ phase complete the phase transition and phase growth;Using SPS sintering and hot pressing sintering process?1400?-2min-30MPa-SPS?1700?-1h-0MPa-hot pressing?,1700? heat for 1h without pressure,due to the poor chemical affinity of the Ni₃ Al liquid phase and the Si₃N₄ phase,although the phase transformation of ???-Si₃N₄ is substantiallycompleted,the phase of ?-Si₃N₄ produced by the phase transformation do not grow into whiskers.The feasibility of the in-situ ?-Si₃N₄ whiskers is difficult to be achieved,then the toughening of composites was carried out by adding ?-Si₃N₄ whisker directly,the densification process,phase composition,microstructure and mechanical properties of WC-6wt.% Ni₃Al-x wt.% Si₃N₄?x = 0,2,4,6,8?composites were investigated.It is found that the trend of density,hardness,fracture toughness and transverse rupture strength of the composites are almost the same,they are first reduced and then increased with the addition of?-Si₃N₄ phase and the increase of the content of ?-Si₃N₄ phase.WC-6 wt.% Ni₃ Al composites have the best comprehensive mechanical properties,while for the composites added with?-Si₃N₄ phase,the obtained bulk WC-6 wt.% Ni₃Al-6 wt.% Si₃N₄ possesses a high hardness,fracture toughness and transverse rupture strength of 18.01 GPa,9.26 MPa×m1/2,1423 MPa,respectively.Study on micro-texture laser processing and defect suppression of composite surface of WC-6 wt.% Ni₃Al-x wt.% Si₃N₄?x=0,4,6,8?.The effect of different laser power on the surface micro-texture morphology and properties was investigated,it was found that the surface micro-structure with the laser power of 20 W had the largest aspect ratio;The effects of Si₃N₄ content on the micro-structure and properties was investigated,the results show that the micro-structure of the composites without Si₃N₄ phase has the largest aspect ratio;Laser processing in water,liquid nitrogen and ice layer is used instead of air processing to improve the surface micro-texture processing quality,it was found that the surface micro-textures were well machined under the 0.5mm ice layer,and the Vickers hardness in the vicinity of the grooves was larger than that near the surface micro-texture in the air.