In Situ Synthesized TiC /ti-matrix Composites With Hollow Cathode Sintering Process

Titanium matrix composites have caused a wide range of attention in recent years for its high specific strength, high specific modulus and high temperature properties. However, the high cost and the difficulty in processing have restricted the mass application of titanium matrix composites alloys. As a new process, in-situ synthesis of particulate reinforced titanium matrix composites has exhibited a great attrictivity, due to excellent high despersity of reinforcements, compatibility between reinforcements and matrix that results a strong bonding, lower cost, well as easy hangdling. With characteristics of rapid heating to high temperature, hollow cathode plasma sintering is a promising novele powder metallurgy sintering technology. Currently, the research that uses hollow cathode sintering to produce Particulate Reinforced Titanium Matrix Composites has not yet been reported.Adopting hollow cathode plasma sitering, a TiC/Ti-6Al composite was preparated by ways of in-situ synthesiz. The reinforcement TiC was synthesized through the adding of fine graphite powder and then reacting with matrix Ti during sintering. According to the fundmental theory of hollow cathode discharge, the effects of process parameters on the sintering temperature and density of compacts were dicussed. Then a special assistant cathode structure was designed to produce a suitable hollow cathode discharge that a homogenius distribution of temperature was guaranteed.Hollow cathode discharge plasma sintering titanium alloy process can be divided into three stages: preparing, heating and preservating. In the process of sintering, the density of sample increased with the elevating of sintering temperature. It was also found that holding time had a remarkable influence to the final density of the compacts.Through seriers experiments, the optimium process parameters were concluded as below: the content of added graphite is 0.9 wt%, the working pressure is about 30Pa, the distance between the assistant cathode and compacts is about 10mm sintered at 1300℃for 6h. SEM observation indicated a well interfacial bonding between in-situ synthesized TiC particulates and Ti matrix was obtaimed. The bending tests showed that the fractureing in is in a feature of brittle mechanism.A set of wear experiments for composites with different graphite contents were also carried out. The results showed that owing to the existence of the in-situ synthesized TiC particles. The hardness of titanium matrix composites has been increased, and the wear resistances were also greatly improved.