Diamond is added into hard alloy to increase its abrasive resistance. But the key problem of diamond-hard alloy composite is its low bending strength and low impact resistance, and that confined its practical use. In this dissertation, the factors influencing the strength and impact resistance of diamond–hard alloy composite are studied by analyzing the relationship between diamond and WC size, diamond concentration and fibrous reinforcement mechanism. At the base of theoretical analysis and experimental investigation, it is realized that the relationship between diamond and WC size should meet a certain confined condition to increase composite’s strength and impact resistance. Diamond concentration should be controlled in a certain range according to the impact energy. Carbon nanotube can increase the bending strength and hardness of micron diamond-hard alloy composite. First, the influence of diamond concentration on the bending strength of diamond-hard alloy composite was studied. With the diamond concentration increases, the bending strength will be lowered sharply. When the concentration increases from 50% to 100%, the bending strength will reduce by 50%. But the wearing resistance will continually increase. In the light of production requirement, the bending strength and wear resistance of diamond-hard alloy composite will be required, and then diamond concentration is defined .For wear resistant material, diamond concentration can be increased to 100% or more. For shock resistant material, the concentration should be decreased to meet the requirement of the bending strength and impact resistance. Second, the influence of diamond and WC sizes on the bending strength was studied from the point of packing and the replacement theory. The relationship between diamond and WC size had obvious influence on diamond-hard alloy composite’s bending strength, the packing model was adopted suitably. The bigger the ratio of diameter of WC granule to the diameter of diamond was, the less the influence of the composite’s bending strength was. When the ratio of the WC granularity to the diamond granularity was changed from 1: 1 to 750: 1, the bending strength of the composite can be enhanced by 24.6%. In order to maintain the WC framework of hard alloy invariable, the biggest diameter of the enhancement material (diamond) should not be bigger than dB .It is given by: d≤dB =0.45dA where, d– the diamond particle size; dB–the void diameter between framework materials; dA– the WC particle size. Diamond particle replacing WC particle certainly cannot improve the composite’s bending strength. The reasons are as following. 1.After the diamond particle substituting for crystal lattice position of the WC particle, there are not the good chemical bond relations between the diamond particle and other WC particle, and original chemical bond is destroyed between the original WC particles. 2、It is easy to form the crack because the diamond particle shape is irregular . Third, the diamond-hard alloy composite enhanced with carbon nanotube was theoretically analyzed and the sintering experiments were carried out. According to the usage, the composite can be divided into structural composite and functional composite. The structural composite is basically composed of strengthen body and matrix. According to shape, strengthen body can be distinguished with particle (zero dimension), fiber (one dimension), sheet (two dimension) and woven material (three-dimension),etc.. 1. On condition that accord with the fiber and the strengthen theory for the material requirement, when the carbon nanometer tube CNT2 is added to 0.3%, it can improve the bending strength of micro powder diamond - hard alloy composite effectively, the improved amplitude reaches 24.9% . And it also can improve its hardness solidness, the improved amplitude reaches 5.1% . However, when the addition exceeding 1%, it results in the bending strength of composite dropping (author"s early experiment instead, the adding amount of the carbon nanotube is 1%, 3%, 5%, 7%, the bending strength of the carbon nanotube-diamond-hard alloy composite is reduced sharply, when the joining amount of the carbon nanotube is 7%, the composition of the sintered body is mainly a carbon nanotube, the bending strength at this moment can be ignored, the sintered body present fragility and black). 2. Fine particle cobalt whose granularity is 1-3μm and carbonyl cobalt powder can improve diamond-hard alloy composite performance. The granularity and performance of cobalt powder, nickel powder have more influence on sintered body. 3. The compounding way has very important influence on enhancement effectiveness of the carbon nanotube. Firstly, there is a depurated and decentralized processing to deal with the carbon nanotube. Secondly, rerolling or shaking is used, in this way, the length of carbon nanotube can be controlled effectively. At present, the quality, purification, coating and decentralization of the carbon nanotube are still the subject which is studied continually both at home and abroad. Generally speaking, WC size is changed from thickly to thinly, then the bending strength of hard alloy drops, and the abrasive resistance is improved. But except to the nanometer material, the nanometer material can improve intensity and hardness of the material at the same time, therefore ,it is a better way to use carbon nanotube for strengthening nanometer diamond--nanometer WC hard alloy composite. 4. Along the quality, purification, coating and decentralization of the carbon nanotube are improced, the enhancing action becomes better and better . Carbon nanotube can bear 1,500℃high temperatures, and displays the high wearing resistance in the superficial project application. Carbon nanotube can be used to strengthen the cobalt-base tungsten carbide hard mental alloy. 5. The mechanism of carbon nanotube to strengthen micron diamond-hard alloy composite has been studied. The mechanism include conventional fibrous reinforcement’s crack bridge association, crack deflection and extraction effect, and it also has some special effects. Long carbon nanotube enhancement function is conventional, but the one that is shorter than basal body’s WC size also has the better enhancement function. The main crack’s original of micron diamond-hard alloy composite is micron diamond, micron diamond’s adding results in hard mental alloy’s bending strength falling down rapidly. The distribution zone of micron diamond is the composite’s chief strength weak area, and the crack starting area. The micron diamond size is 0.1μm, which is shorter than the tungsten carbide’s size 6~8μm. If short carbon nanometer tube can reach above 0.1μm, it can cross the micron diamond strength weak area and play the enhancement role. (1)As for materials mechanics, micron diamond results in the bending strength falling, high-strength short fiber crosses the weak strength area caused by micron diamond , which has the action of enhancing. (2)As for fracture mechanics, the crack tip caused by 0.1μm (namely 100nm) micron diamond is very small, high-strength short fiber can weaken the tip crack expanding and heighten fracture toughness property by crossing the crack tip. (3)As for the spatial structure, high-strength short fiber separates like stereo reticulation by joining, overlapping, contacting; Carbon nanometer tube’s tubular structure and large slenderness ratio are propitious to combine with agglomerant. Its high-strength performance makes it become sintered body’high-strength part. It has important meaning that carbon nanotube enhances diamond-hard alloy composite, and it is also a effective new method . The method should be researched more, the technology measure is improved to control carbon nanotube’s length and decentralization and advance enhancing effect. Forth, carbon nanotube- micron diamond-hard alloy composite button insert is studied. Carbon nanotube-micron diamond-hard alloy composite button insert is manufactured elementarily, whose diameter is 12mm and highness is 14mm. The performance of sintered button insert is tested: (1) The performance test is compared between the composite’s superhard part and cylinder basal part. The abrasive resistance of the head superdrd part is 3 times of button insert hard alloy part. (2) The button insert sintered thirdly is put in the impact resistance tasting equipment which is made oneself to test the performance. On condition that the surface is not disposed and polished, has helicoids, and pits exists in the head, its abrasive resistance is 17J. From composite button insert crack form to see , 8 button inserts is cracked , the superhard part is combined with basal body perfectly ,they are both cracked vertically. From the fracture to see, preferable alloying is actualized for button insert. (3) Both upper and lower heading dies are improved, which makes them use dependably, be propitious to remove from mould, and can be reused. They also can improve the sintered performance effectively. (4) The delamination phenomenon is overcomed.(a) The cobalt content of superhard part is a little higher than basal body,the difference of the cobalt content reduces the gap of the bending strength .(b) In the process of sintering , upper and lower heading dies are confined with superhard part perfectly ,which can reduce the gap of the basal body’s bending strength.(c) Upper and lower heading dies are pressed equably at the same time and are contacted by spheric face, which can get over superdard part’s delamination phenomenon. (5) The impact resistance of“superhard part”approaches with cylindrical part, they both appear splitting fracture. (6) Carbon nanotube strengthening action increases the bending strength of superhard part, meanwhile, the difference of the bending strength is reduced between superhard part and cylindrical part. Owing to Carbon nanotube adding in composite, superhard part presents deep color, its color is lively compared with basal body. So it is approved that Carbon nanotube exists in sintered body from macroscopic view. Through the performance parameter measured compressively ,it is declared that diamond-hard metal alloy new composite button insert should be studied meticulously, and its performance should be enhanced.