The Effects Of Rare Earth Additives On The Properties Of Iron-based Diamond Composites

Sawing is a very important procedure in processing of natural stone from raw materials to end products. As a sawing tool, the properties of a diamond impregnated circular saw-blade are of special importance in determining the machining cost and production efficiency. Sawing is carried out by diamond grits which are embedded into a metal matrix, so whether diamond grits can be tightly held in the metal matrix, and whether their cutting abilities can be fulfilled directly determine the sawing performance and the life of the diamond saw-blade. However, due to the low adhesive strength between diamond particles and metal matrix, diamond grits are prematurely pulled out during cutting, which leads to an increase of tool cost and a decrease of machining efficiency. Therefore, improving and increasing the adhesive strength between diamond particles and metal matrix is one of the most important tasks to be solved in the investigation of diamond tools.Among many kinds of metal matrixes for diamond saw-blade segments, the application of iron powder has gained extensively attention in recent years due to its predominant advantages: plentiful supply and low price. However, iron powder is liable to oxidation, which will reduce the surface activities of the powder and hinder the sintering process. In addition, under high sintering temperatures, iron powder can result in the graphitization of diamonds. These two reasons will affect the mechanical properties of the metal bond and its retention capacity. As a result, the wear resistance of metal bond is poor and diamond grits can be easily pulled out from the matrix, thereby shortening the life of the saw-blade. Allowing for their particular physical and chemical properties, rare earth elements were added into metal matrixes in the present study to solve the problems as stated above. This dissertation aims at revealing the micro-mechanism of the rare earth's effects on improving the properties of iron-based diamond composites. In addition, to combine the investigation of the effects of rare earth with the effects of strong carbide-forming element Ti, TiH2, which has been widely used as a carbide-forming element, was also added to the iron-based matrix in order to evaluate its effects on the metal bond and diamond segments. The effects of different types and amount of rare earth, TiHi, different sintering temperature on the properties and micro-mechanism were systematic studied. The study of this dissertation can be summarized as follows:1. The effects of the types and amount of rare earth elements as well as hot-pressing sintering temperature on the mechanical properties of Fe-based metal bond and diamond composites either containing or not containing TiH2 were studied by means of orthogonal test and variance analysis. The significance of their effects was evaluated and the optimal National Natural Science Foundation of China (50175030) and Natural Science Foundation of Fujian Province in China (E0010025).sintering temperature, type and amount of rare earth were found.2. Optical microscope, SEM (including EDS) and XRD were used to study the microstructures and images of fractured surfaces of the metal bonds and diamond segments, the products formed at the diamond-matrix interface, the elements distribution and phases formed in the segments were also analyzed in order to reveal the micro-mechanism of the effects of rare earth elements and TiH2 on the mechanical properties of iron-based bond and diamond composites under different sintering temperatures.3. Saw-blades made of iron-based matrix with different additives were fabricated to carry out the sawing of granite. The consumed spindle power, cutting forces and the wear resistance of the saw-blades were measured. SEM observations on the worn surfaces of saw-blade segments were also carried out to reveal the wear characteristics of diamond grits and the metal matrix as well as the bonding at the diamond-matrix interface. The improving effects of different additives on the sawing performance were comprehe...