Development and performance of heat insulation coatings for hot rolling of titanium alloy and superalloy rings

摘要

In recent years, with the continuous development of the equipment manufacturing industry, the seamless rings made of high-performance titanium alloys and superalloys have been widely used. These seamless rings mainly include aeroengine casing rings, carrier rocket capsule rings, gas turbine rings, oil/gas pipeline rings and so on. The metal ring hot rolling technology has become an irreplaceable manufacturing technology with its characteristics of low material consumption, high efficiency and high performance. However due to the special features of titanium alloys and superalloys, they have poor thermal processing plasticity and high processing sensitivity, thus cracks occur easily during metal temperature drop in hot rolling process. At the same time, the metal surface oxidation in the heating process also affects the surface quality and rolled parts performance. Therefore, using heat insulation and protective coatings is the most effective and easiest solution for the problem. In view of the above problems, Beijing Tianlichuang Glass Technology Development Co., Ltd. has successfully developed the water-based heat insulation coatings for titanium alloy & superalloy hot rolling at different rolling processes (different temperatures and different holding times). The coatings are coated on the metal surface at room temperature and dried before the billets are sent to furnace for heating. During the heating process, the coatings can prevent metal oxidation at high temperature and preserve heat during the billet transfer & rolling process without generating lubrication effect. These heating preservation coatings use a variety of crystalline non-metallic oxides, minerals and non-crystalline glass powders as major solid base materials, and blended with additives, adhesives and water to create suspensions, then applied to metal surface via brushing or spraying before heating. When design coating formulas, in order to realize good compatibility with the metals and right high temperature viscosity & expansion coefficient so as to achieve perfect match with different hot rolling processes, we should consider specific hot rolling process of titanium alloy & superalloy rings, that is, heating temperature, holding time, furnace atmosphere, and hot rolling condition. The heat insulation coatings can solve the problem of billet heat preservation & protection in the titanium alloy / superalloy ring hot rolling process, meanwhile reduce the surface cracks after hot rolling, making the metal easier to obtain even and fine microstructures. Also, the coatings are easy to use, non-toxic and environment friendly.