Fabrication And Performances Of Brazed Diamond Wire Saw With Regular W-Coated Diamonds Distribution By Glue-Dispersion Method

Reinforced concrete has been widely used in the engineering of buildings,roads,bridges,tunnels and seaports,and it is believed that the demand for demolition and restoration of these reinforced concrete structures will keep high for a long term,with the in-depth development of country's urbanization.The diamond wire saw is one kind of diamond cutting tools,which is very suitable for cutting big-section,irregular-section,and underwater concrete units.However,some drawbacks have been exposed when traditional diamond wire saws(e.g.electroplated or hot-pressed beads)are utilized to destructure reinforced concretes.For instance,cutting chips of steel will probably stick to the bead surface,making it difficult to remove the iron chip.This phenomenon will result in a worse cooling performance for the heat dissipation of diamond wire saws.In order to solve these aforementioned problems,this dissertation introduces a novel method of brazing tungsten-coated diamonds onto the bead substrate,using glue-dispensing technique to fix diamond in a regular arrangement.The invented new wire saw has many superior advantages such as high bonding strength of diamonds,high protrusion of cutting edges,and enough space for chipping.Thus it is very likely to become a useful cutting tool for machining reinforced concretes with high efficiency.And here are some highlights achieved in this dissertation:(1)Four different kinds of diamonds were heated at high-temperatures for a thermal treatment,and then the friction-wear tests were carried out to evaluate their abrasion resistance based on the features of wear morphology.In addition,Raman spectrum was employed to compare the graphitization extent of brazed W-coated diamond and brazed Ti-coated diamond after the same brazing process.The results show that brazed W-coated diamonds suffer less chemical erosion than brazed Ti-coated diamonds,because the graphitization extent of brazed W-coated diamonds decreases approximately 50%than that of brazed Ti-coated diamonds,and the corresponding toughness index enhances by 12%.The element distribution at the metallurgical bonding interface between Ni-Cr filler alloy and W-coated diamond(or Ti-coated diamond)was studied by EDX map-scanning,which demonstrates that tungsten coatings still exist after the brazing process while titanium coatings have been destroyed or dissolved into the Ni-Cr molten alloy.(2)Three different patterns of grit distribution with distinct diamond concentrations and chipping space were designed through AutoCAD software.These patterns of diamond distribution include a highly aligned arrangement,a slanted arrangement at a30°angle,and a staggered arrangement.In addition,the brazing parameter of the glue-diamond bead were introduced.Moreover,the micro mechanism about how excessive brazing temperature influences the accuracy of grit distribution were also discussed.The desired dosages of filler alloys were calculated on the basis of a theoretical model.An ideal morphology of brazed diamonds was observed and nearly37~52% of the diamond grit was wrapped in the brazing layer,as the weight ratio of filler alloy to uncoated diamond was 3:1,or the weight ratio of filler alloy to W-coated diamond was 2:1.(3)According to above research results,several brazed diamond wire saws with different grit distributions were fabricated.The diamond distributions(highly aligned arrangement,tilted arrangement at a 30°angle,a staggered arrangement)are in line with glue dots patterns obtained by the glue-dispensing method.Besides,tungsten-coated diamonds were applied to manufacture a brazed wire saw and W-coated diamonds were arranged in a slanted line.Subsequently,a series of field tests were carried out to investigate the application potential of this novel brazed diamond wire saw.The brazed wire saws with slanted-line diamonds or staggered diamonds showed a significant advantage on the cutting efficiency and tool lifespan than other wire saws with irregular diamond distribution.The highest cutting speed of the wire saw with slanted diamond pattern could reach0.10~0.12 m~2/min,and the longest lifespan of the wire saw with staggered diamond pattern could achieve 5.6 m~2.However,the brazed wire saw with highly aligned diamond pattern showed a poor wear resistance,probably due to its lowest diamond concentration.On the contrary,the wire saw using W-coated diamonds possessed the best performance in the aspect of abrasion resistance,whose lifespan was 20% higher than traditional brazed wire saws using uncoated diamonds.