| Wear is one of the main forms of material failure.80%of the mechanical materials cons?med on the wear,the equipment on the vicious accidents due to the transition wear and lubrication failure.Therefore,the development of high-performance wear-resistant steel materials,to reduce the loss of material wear process,improve the life of mechanical equipment has a vital significance.Low-alloy wear-resistant steel plate as an important wear-resistant steel materials,alloy content is low,good overall performance,production flexibility and cheap and so hold,is widely used in construction machinery,mining machinery and metallurgical machinery and other equipment production manufacture.The wear failure and strength-harden mechanism of Cr-Ni-Mo and Mo-Ti-B high strength-toughness martensite steels as well as high nitrogen austenitic steel have been studied.Both microstructure and micro-hardness of longitudinal section of maxim?m deformation area vertical partwith wear surface have been tested by SEM,TEM,EBSD and HV micro-hardness.The mechanism of material hardening and wear failure were discussed.(1)The impact wear experiments of Cr-Ni-Mo and Mo-Ti-B high strength-toughness martensite steels were examined using an MLD-10 dynamic load impact wear testing machine.The hardening degree of subsurface was characterized.The results showed the wear resistance of material gradually decreased with the increase of wear time under 2.5 J impacting energy.However,the wear resistance of Cr-Ni-Mo steel is superior to Mo-Ti-B steel with the increase of wear time under 3.5 J impacting energy.Cr-Ni-Mo steel in the hard abrasive(white corund?m)wear a larger amount under low impact load,while under high impact loads,the wear almost the same.Sub-surface hardness was significantly higher than the hardness of the matrix,with the sub-surface depth increases,the degree of work hardening gradually reduced.(2)The microstructural variation under 2.5 J impacting energy with 2 hours has been analysis by EBSD.The statistical results indicated the high and low angle grain boundary is 63.6%and 36.4%of the Cr-Ni-Mo steal,the high and low angle grain boundary is 61.2%and 38.8%of the Mo-Ti-B steal,the high and low angle grain boundary is 47.4%and 52.6%of the Cr-Ni-Mo steel after wearing.And Mo-Ti-B steel is 61.2%and 38.8%respectively.The increase of the small angle density of Cr-Ni-Mo steel leads to the improvement of the material strength and the improvement of the wear resistance of the material.While the grain boundary angle of Mo-Ti-B steel is not obvious.(3)The wear resistance of Cr-Ni-Mo steel decreased first and then increased under 3.5 J impacting energy.The maximal deformation zone of sub-surface was observed by SEM and TEM.The experimental results show that the matrix showed the character of low temperature tempering,martensite structure gradually decomposed into ferrite matrix and massive hard carbides under a size of 500 nm.The hard carbides were confirmed as epsilon-carbide by TEM diffraction pattern.Andcarbides played a skeleton support effect by reducing the contact between matrix and abrasive,so as to improve the wear resistance of materials.However,martensitic matrix in wear surface area was fast decomposed into ferrite and cementite of Mo-Ti-B steel under 2.5 J impacting energy.With the further increase of wear time,carbide grew up continuously,and broke away from coherent relationship with matrix.The weak connection between carbide and matrix leaded to the formation of micro cracks to decrease continually the wear resistance of material.(4)The strength-harden mechanism of different deformation strengthening high nitrogen austenitic steel have been studied by the variation of micro-hardness and microstructure in longitudinal section with wear morphology in wear surface.The results showed that the subsurface hardening range of 10mm thickness high nitrogen steel was 438.45HV to 497.09HV under 1.5 J,2.5 J and 3.5 J impacting energy,and the hardening depth was closed to 1400 ?m.The subsurface hardening range of 50mm thickness high nitrogen steel was 438.45HV to 497.09HV,and the hardening depth was closed to 1000 ?m.The work hardening degree was enhanced gradually,cutting mark and furrow decreased,and fatigue spalling pit increased with the increased of impacting energy.The EBSD statistical results indicated 10mm high nitrogen steel grain angle increased from 59.4%to 73.7%,and50mm high nitrogen steel grain angle increased from 68.6%to 73.6%after 3.5 J impacting energy.And the high angle grain boundary of 50 mm high nitrogen steel was less than 10 mm high nitrogen steel,resulted in a worse toughness of the material. |
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