CN-121988515-A - Preparation method of graphite coating on surface of titanium tube

Abstract

The invention relates to a preparation method of a graphite coating on the surface of a titanium tube. The method comprises the steps of (1) cleaning the outer side of a titanium pipe, inserting a core rod with the diameter being the same as the inner diameter of the titanium pipe into the titanium pipe, (2) carrying out low-temperature pressureless sintering on the titanium pipe with the core rod inserted therein, coating graphite slurry on the outer surface of the titanium pipe, and then drying in air, (3) placing the titanium pipe with the core rod inserted therein and the graphite slurry coated on the outer surface thereof into hot isostatic pressing equipment for constant-temperature and constant-pressure sintering, and (4) cooling the titanium pipe to room temperature along with a furnace after the sintering is completed, extracting the core rod, thereby obtaining the graphite coating on the surface of the titanium pipe with a compact titanium/graphite interface. The preparation method provided by the invention realizes the preparation of the graphite coating on the surface of the titanium tube through a simple and feasible sintering process, is quick, efficient, short in process and low in cost, and can prolong the service life of the die while improving the quality of the titanium tube product.

Inventors

• LI JINGKUN
• WU BOWEN
• FU BINGUO
• DONG TIANSHUN
• ZHAO XUEBO
• LI GUOLU

Assignees

• 河北工业大学

Dates

Publication Date

20260508

Application Date

20260309

Claims (5)

1. 1. The preparation method of the graphite coating on the surface of the titanium tube is characterized by comprising the following steps: (1) Cleaning the outer side of a titanium pipe, and then inserting a core rod with the diameter the same as the inner diameter of the titanium pipe into the inner side of the titanium pipe; (2) Carrying out low-temperature pressureless sintering on the titanium pipe with the mandrel inserted therein obtained in the previous step at 300-400 ℃ for 30-60 min, coating graphite slurry on the outer surface of the titanium pipe, and then drying in air; the thickness of the graphite slurry coated on the outer surface of the titanium tube is 200-300 mu m; (3) Placing the titanium tube with the core rod inserted into the titanium tube and the graphite slurry coated on the outer surface of the titanium tube into hot isostatic pressing equipment, and sintering the titanium tube for 30-60 min at a constant temperature and a constant pressure of 300-500 ℃ and 100-200 MPa; (4) And after sintering, cooling the titanium tube along with a furnace to room temperature, taking out the core rod, and extracting the core rod to obtain the graphite coating on the surface of the titanium tube with a compact titanium/graphite interface.
2. 2. The method for preparing a graphite coating on the surface of a titanium tube according to claim 1, wherein in the step (2), the volume fraction of graphite in the graphite slurry is 10% -25%.
3. 3. The method for preparing a graphite coating on the surface of a titanium tube according to claim 1, wherein the titanium tube is a pure titanium or titanium alloy tube.
4. 4. The method for preparing a graphite coating on the surface of a titanium tube according to claim 1, wherein the mandrel is a high-hardness hard alloy or a high-strength tool steel.
5. 5. The method for preparing the graphite coating on the surface of the titanium tube according to claim 1, wherein the thickness of the graphite coating on the surface of the titanium tube obtained in the step (4) is 50-150 μm.

Description

Preparation method of graphite coating on surface of titanium tube Technical Field The invention belongs to the technical field of coating preparation, and particularly relates to a preparation method of a graphite coating on the surface of a titanium tube. Background Titanium and its alloy have excellent comprehensive mechanical property, high fatigue strength, good corrosion resistance and biocompatibility, and are widely used in the fields of aerospace, mechanical automation, biomedical engineering and the like. Titanium and its alloy tubing (hereinafter referred to as "titanium tubing") have been widely used in the aerospace industry, including the manufacture of aircraft skeletons, engine core components, and complex hydraulic systems, by virtue of their high strength, low density, and excellent corrosion resistance. Currently, extrusion and rolling are critical processes for manufacturing titanium tubes. Titanium is extremely easy to react with an iron-based die at high temperature to generate brittle intermetallic compounds, so that the die is worn and the product is cracked. Therefore, a graphite layer is usually required to be added between the titanium tube and the die, and the titanium and the die are effectively isolated by virtue of excellent high temperature resistance and chemical inertness of graphite, so that the damage of the die and products is prevented, the quality of the titanium tube product is improved, and the service life of the die can be prolonged. Meanwhile, graphite can play a role in lubrication in the pressurizing process. The method for adding graphite on the surface of a titanium tube is mainly to spray graphite spray (Cui Qinglong, chen Jian, zhao Qianqian, he Xiaofeng, yang Min, cong Yupeng, wang Haojiang, zhang Qun, li Zhongyuan) on the surface of the titanium tube, a non-standard titanium alloy special-shaped tube and a processing method thereof [ P ] application number 202311827615.7, application date 2023-12-27), and then drying in air to form a graphite coating. However, the thickness of the graphite layer on the surface of the titanium tube is limited by the spraying method, and the thick graphite layer is difficult to prepare, so that the graphite layer is frequently fallen off in subsequent processing, the titanium tube and the die are directly rubbed, the surface quality of the titanium tube is reduced, and the service life of the die is shortened. In order to prepare a thick graphite layer on the surface of a titanium tube, researchers uniformly smear a graphite lubricant on the surface of the titanium tube (Gao Jie, gao Yuguang, wang Jinyong, liu Fujiang, ji Xilun. Extrusion forming method of titanium alloy seamless tube and its product [ P ]. Application number: 20241929593. X, application day: 2024-12-26), graphite emulsion (Xue Gongjun. A high-strength corrosion-resistant titanium copper composite rod and its manufacturing method [ P ]. Application number: 202111299949.2, application day: 2021-11-4), and then dry in air to make the graphite layer with a thickness of about 30 μm adhere to the surface of the titanium tube, but during the subsequent extrusion processing, the graphite layer on the surface of the titanium tube often breaks away from the surface of the titanium tube due to friction, causing direct contact and friction between the titanium tube and the mold, thereby losing the protective effect of graphite. The method is characterized in that a thicker graphite layer is difficult to combine with a titanium tube substrate by conventional methods of spraying, smearing, and the like, the main reasons are that the surface roughness of the titanium tube is low, so that the graphite is difficult to adhere, and the interface bonding strength of the graphite and the titanium tube is low due to the fact that the graphite layer naturally dried in an air environment is not tightly combined with the titanium tube substrate. Therefore, a method for preparing a graphite layer with dense interface bonding on the surface of a titanium tube is highly demanded. Disclosure of Invention The invention aims at providing a preparation method of a graphite coating on the surface of a titanium tube aiming at the limitation of the prior art. The method adopts a twice low-temperature sintering process, forms a layer of rough oxide film on the outer surface of the titanium tube through low-temperature pressureless sintering, is more beneficial to the adhesion of the subsequent graphite, uniformly coats graphite slurry on the outer surface of the titanium tube, and adopts low-temperature hot isostatic pressing sintering to realize densification of the graphite layer and a graphite/titanium interface. The preparation of the graphite coating on the surface of the titanium tube is realized by a simple and feasible sintering process, and the preparation method is quick, efficient, short in process and low in cost, so that the graphite layer attached to the surface of the titanium