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CN-121972678-A - Heat treatment method for synchronously improving plasticity of zirconium-niobium alloy formed by laser powder bed fusion and performance of surface ceramic layer

CN121972678ACN 121972678 ACN121972678 ACN 121972678ACN-121972678-A

Abstract

The invention belongs to the technical field of zirconium-niobium alloy, and discloses a heat treatment method for synchronously improving the plasticity of zirconium-niobium alloy formed by melting a laser powder bed and the performance of a surface ceramic layer. The method comprises the steps of placing zirconium-niobium alloy formed by melting a laser powder bed in a heat treatment furnace, preserving heat at 650-750 ℃ for 10-30min under the atmospheric environment, cooling to 550-650 ℃, preserving heat for 20-60min, continuously cooling to 400-500 ℃, preserving heat for 20-60min, repeating the cycle, and cooling to room temperature along with the furnace. The invention synchronously realizes the strengthening and toughening of the alloy matrix and the preparation of the surface high-performance ceramic layer, the microhardness of the treated alloy surface is greatly improved, a thicker compact oxide layer is formed, the loss of tensile strength is reduced to the minimum, the elongation after fracture is greatly improved, and the difficult problem that the 'strong plasticity' and the 'wear resistance' of the zirconium-niobium alloy in the traditional process are difficult to cooperatively improve is solved.

Inventors

  • DU JUN
  • LI AIWEN
  • SONG CHANGHUI
  • LEI HAOYANG

Assignees

  • 华南理工大学

Dates

Publication Date
20260505
Application Date
20260106

Claims (8)

  1. 1. A heat treatment method for synchronously improving the plasticity of zirconium-niobium alloy formed by laser powder bed fusion and the performance of a surface ceramic layer is characterized by comprising the following steps: (1) Pretreating and initially oxidizing, namely placing zirconium-niobium alloy formed by melting a laser powder bed into a heat treatment furnace, and preserving heat at 650-750 ℃ for 10-30 min under the atmospheric environment; (2) Medium-temperature oxidation and tissue relaxation, namely cooling the alloy treated in the step (1) to 550-650 ℃ and preserving heat for 20-60min; (3) Regulating and controlling a circulating temperature field, namely continuously cooling the alloy treated in the step (2) to 400-500 ℃, and preserving heat for 20-60 min; (4) And (3) circularly repeating the steps (1) - (3), and cooling to room temperature along with the furnace after the last circulation step (3) is completed, so as to obtain the zirconium-niobium alloy with strong plasticity and high surface performance ceramic.
  2. 2. The heat treatment method for simultaneously improving the plasticity of the zirconium-niobium alloy and the performance of the surface ceramic layer by fusion forming of a laser powder bed according to claim 1, wherein the number of repetition in the step (4) is 3-5.
  3. 3. The heat treatment method for synchronously improving the plasticity of the zirconium-niobium alloy formed by melting a laser powder bed and the performance of a surface ceramic layer according to claim 1, which is characterized in that in the step (1), the temperature is kept at 650-750 ℃ for 10-30 min, the temperature is raised to 650-750 ℃ at a rate of 6-15 ℃ per minute, and then the temperature is kept for 10-30 min; The cooling rate in the step (2) is 2-7 ℃ per minute, specifically, cooling to 550-650 ℃ at 2-7 ℃ per minute, and then preserving heat for 20-60 minutes; The continuous cooling rate in the step (3) is 2-7 ℃ per minute, specifically, cooling to 400-500 ℃ at 2-7 ℃ per minute, and then preserving heat for 20-60 minutes.
  4. 4. The heat treatment method for synchronously improving the plasticity and the surface ceramic layer performance of the zirconium-niobium alloy formed by melting a laser powder bed according to claim 1, wherein the zirconium-niobium alloy in the step (1) is Zr-2.5Nb alloy.
  5. 5. The heat treatment method for simultaneously improving the plasticity of a laser powder bed melt-formed zirconium-niobium alloy and the performance of a surface ceramic layer according to claim 4, wherein the Zr-2.5Nb alloy contains the following components ：Nb 2.4~2.8%,O 0.09~0.12%,Hf < 0.005%,Fe < 0.015%,Ca < 0.002%,Cu < 0.002%,N < 0.003%,H < 0.002%,C < 0.003%, by mass percent, and the balance being Zr and unavoidable impurities.
  6. 6. The heat treatment method for synchronously improving the plasticity of the zirconium-niobium alloy formed by melting a laser powder bed and the performance of a surface ceramic layer according to claim 1 is characterized in that the whole heat treatment process is carried out in air without additional controllable atmosphere protection.
  7. 7. The heat treatment method for synchronously improving the plasticity of the zirconium-niobium alloy formed by melting the laser powder bed and the performance of the surface ceramic layer according to claim 1 is characterized in that the zirconium-niobium alloy formed by melting the laser powder bed is ground and polished and then placed in a heat treatment furnace; the Zr-2.5Nb alloy in step (1) is prepared by: s1, selecting Zr-2.5Nb alloy powder with the grain diameter of 20-150 mu m; and S2, adopting LPBF technology to print and mold layer by layer in a protective atmosphere to obtain a zirconium-niobium alloy sample.
  8. 8. A strong plastic and surface high performance ceramic zirconium niobium alloy obtained by the method of any one of claims 1to 7.

Description

Heat treatment method for synchronously improving plasticity of zirconium-niobium alloy formed by laser powder bed fusion and performance of surface ceramic layer Technical Field The invention belongs to the technical field of zirconium-niobium alloy materials, and particularly relates to a heat treatment method for synchronously improving the plasticity of LPBF formed zirconium-niobium alloy and the performance of a surface ceramic layer. Background Zirconium-niobium (Zr-Nb) alloys, particularly Zr-2.5Nb alloys, have been attracting attention more recently because of their elastic modulus closer to human bones, non-magnetic interference, excellent corrosion resistance in physiological environments, and the like. Zirconium niobium alloys are commonly used as implant materials. Existing implant materials often require custom implant devices that are complex in shape and precise in structure. Conventional subtractive manufacturing (e.g., machining) or casting techniques face challenges in such requirements that are costly, long-lived, low-material-utilization, or difficult to form. Laser Powder Bed Fusion (LPBF) is used as an advanced additive manufacturing technology, and provides an ideal solution for producing personalized zirconium-niobium alloy implants with the advantages of nearly unlimited design freedom, efficient material utilization capability and manufacturing complex integrated structures. However, LPBF techniques are based on the rapid-melting forming principle, which is a very high cooling rate and complex physical metallurgical changes during the process, resulting in a formed Zr-2.5Nb alloy ("as-printed") microstructure that is typically elongated needle-like α' martensite. Although the structure state gives higher strength to the material, the problem of insufficient plasticity and toughness is often accompanied, so that strong plastic mismatch is caused, and the mechanical reliability required by the zirconium-niobium alloy as an implant body in bearing is difficult to meet. Therefore, the subsequent heat treatment of the Zr-2.5Nb alloy in a printing state is an essential link for adjusting the microstructure and optimizing the mechanical property. On the other hand, the implant not only bears mechanical load in the service process, but also is exposed to body fluid rich in ions and proteins for a long time, and the severe test of abrasion and corrosion interaction is faced. For dynamic load components such as artificial joints, bone nails and the like, poor wear resistance can lead to continuous generation of wear debris, and the service life of the implant is obviously shortened. The Zr-2.5Nb alloy has limited hardness and wear resistance, which is a short plate used as a joint bearing surface material. In order to improve the surface performance, surface engineering techniques such as thermal oxidation, anodic oxidation, carburization, laser surface modification and the like are generally adopted. Among them, the thermal oxidation technique is favored because of its simple process, cost effectiveness, and the strong bonding of the resulting zirconia (ZrO 2) ceramic layer to the substrate. The process is characterized in that the alloy surface reacts with elements such as oxygen, nitrogen and the like by heating in a controllable atmosphere to form a hard ceramic layer, so that the surface hardness, the wear resistance and the corrosion resistance are obviously improved. The dense oxide layer can also effectively block the release of metal ions to the biological environment. In the prior art, a heat treatment process for regulating and controlling the performance of a zirconium-niobium alloy matrix and a thermal oxidation process for improving the surface performance of the zirconium-niobium alloy matrix are usually two separation steps which are independently carried out in different temperature intervals. For example, chinese patent application CN102260841B discloses a method aimed at obtaining an α/β bimodal structure to promote the strong plasticity of Zr705 alloy, the heat treatment temperature of which is between 800 and 900 ℃. At the higher temperature, the residual stress is eliminated, the phase change is promoted, and the plasticity and toughness of the alloy are improved. Whereas for surface thermal oxidation, as disclosed in chinese patent application CN104818409B, the treatment temperature is typically controlled in the lower range of 550-650 ℃. This is because zirconium has a high proportion of rolling-Bedworth, and has significant volume expansion during oxidation, and if oxidized for a long time at too high a temperature, the thickening of the oxide layer will accumulate huge internal stress too quickly, which is very liable to induce microcracking and even spalling of the coating, and adversely impair its protective function and service life. For the heat treatment process for regulating and controlling the mechanical properties of the zirconium-niobium alloy, as disclose