Research And Application Of Lubricating Coatings In Titanium Alloy Forging

Titanium alloys which have excellent performance were widely used in military and industrial production, of which 80% of the forgings are provided by the forging process, in particular the processing of large forgings shape. In the high temperature forging processing of titanium alloy, the alloy is easily oxide and gas permeability, results in surface hardening and brittle. That make the follow-up processing difficulty. After removing the oxidation layer, resulting in a large waste of resources; and In high temperature, the contact surface interaction of mold and metal deformation has been increasing, So the friction coefficient is increased, it is difficult for forging to stripping, which led to forging of poor quality, the mold life will be shorten. Thus, solving the problem of the oxidation and lubrication of titanium alloy when forging is crucial. At present, home and abroad have developed a variety of antioxidation coatings used for high-temperature forging of titanium alloys, but a general problem is the protective temperature is narrow and unreliable perormance of the coatings. The traditional lubricants can not meet the requirements of high temperature forging, due to it is liable to oxidation and carbonization in high temperature.The development of protective lubricant in this paper, is composed of two combined borosilicate glass powder which have high and low softening temperature. Through the join beteen the organic binder and glass powder to broaden the protective temperature. After the glass powder melted, it also has good lubrication. At the same time, the glass have heat preservation function because of its low thermal conductivity. It is very important for titanium which have high sensitivity deformation temperature. In the forging process heat insulation is also essential, It is significant for high strain rate forming and raising the utilization of the facilities. In this study, the borosilicate glass powder was prepared by melt quenching methods. SiO₂ and B₂O₃ are the basic component of the glass; Low-melting oxides such as Na₂O, K₂Oand Li₂O as flux; Al₂O₃, CaO and BaO as stabilizing agent, The composition get rid of toxic PbO. The glass protective lubricant which is prepared in this paper is non-toxic, non-ferrous contamination. Coating formed on surface is simple.Through comparing the oxidation behavior of the coated and uncoated protection Titanium alloy at high temperature to explore the protective performance of the protective lubricant. Two sample will be placed in the furnace at 600℃, 700℃, 800℃and 900℃to keep warm 1h, the two weighting increment of oxidation at different temperature are different; At 900℃with the increase of holding time to explore the weighting increment. By dint of microscope to observe the oxide layer thickness of the sample; The hardness changes from the center to the surface of the two titanium alloy is test by metallographic microscope, to further verify the protective effect; At last through ESEM line scanning to analysis the element of the titanium alloy surface. By high temperature friction testing machine to test the lubricant friction coefficient, and compare the coefficient of friction with non-protective lubricant results. The results show that Ti alloy can be protected well against oxidation and permeating gas by the glass coating during the heat treatment of 600℃⁹00℃. At 600℃has better lubricating effect.