Titanium alloy part laser cladding crack defect control process method

Abstract

The invention belongs to the technical field of additive manufacturing, and provides a titanium alloy part laser cladding crack defect control process method which comprises the following steps that firstly, titanium alloy powder and a hard particle strengthening phase are conveyed to a powder feeding nozzle through a double-barrel powder feeder, a first powder barrel conveys the titanium alloy powder, and a second powder barrel conveys the hard particle strengthening phase; and secondly, the titanium alloy powder and hard particle strengthening phase is output through a powder feeding nozzle, the titanium alloy powder and hard particle strengthening phase and the thin layer on the surface of the base body are melted at the same time through laser irradiation, and a surface coating metallurgically bonded with the base body material is formed after rapid solidification. According to the technical scheme, the generation of crack defects during laser cladding can be greatly inhibited.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology, specifically relating to a process method for controlling crack defects in titanium alloy parts by laser cladding. Background Technology

[0002] Titanium alloys have low hardness and poor wear resistance. Titanium alloy moving friction components cannot meet the design life and reliability requirements of weaponry during use. Therefore, laser cladding is necessary to prepare a wear-resistant coating on their surface to improve their impact and wear resistance. The wear-resistant coating material mainly consists of titanium alloy powder plus hard particle reinforcing phases. Because the cladding coating material contains hard particle reinforcing phases, its physical properties differ from those of the titanium alloy matrix material, such as melting point, thermal conductivity, coefficient of thermal expansion, and density. Furthermore, laser cladding is a complex physical, chemical, and metallurgical process involving rapid heating and cooling. Temperature gradients and microstructure transformations can introduce significant thermal and microstructure transformation stresses, leading to cracks and defects in the cladding coating, severely affecting its quality. Summary of the Invention

[0003] (a) Technical problems to be solved The technical problem to be solved by this invention is: how to improve the crack defects that appear in the laser cladding coating of titanium alloy.

[0004] (II) Technical Solution To address the aforementioned technical problems, this invention provides a method for controlling laser cladding crack defects in titanium alloy parts, comprising the following steps: Step 1: Titanium alloy powder and hard particle reinforcing phase are conveyed to the powder feeding nozzles through a dual-cylinder powder feeder. Powder cylinder one conveys titanium alloy powder, and powder cylinder two conveys hard particle reinforcing phase.

[0005] Step 2: Titanium alloy powder + hard particle reinforcing phase is output through the powder feeding nozzle. Laser irradiation melts the titanium alloy powder and the thin layer on the substrate surface at the same time, and then solidifies rapidly to form a surface coating that is metallurgically bonded to the substrate material. Step 3: When performing the first layer of laser cladding, only powder cylinder one is turned on. When performing the second layer and subsequent laser cladding, powder cylinder one and powder cylinder two are turned on simultaneously. This allows the first layer of laser cladding to be clad only with pure titanium alloy as a transition layer, which serves as a preheating layer to reduce thermal stress and structural stress, improves the fluidity of the molten pool, and suppresses the generation of crack defects during laser cladding.

[0006] Furthermore, to ensure uniform powder feeding, both titanium alloy powder and hard particle reinforcing phase are split in two at the powder feeding nozzle and output through four powder feeding nozzles.

[0007] (III) Beneficial Effects Compared with the prior art, the present invention has the following beneficial effects: based on the fact that the first layer of laser cladding is made of pure titanium alloy as a transition layer, and both the transition layer and the substrate are titanium alloys, the thermal stress and structural stress between the coating and the substrate interface can be reduced. At the same time, the transition layer can play a preheating role to reduce the temperature difference between the coating and the substrate interface, that is, reduce thermal stress, and improve the fluidity of the molten pool to a certain extent. This process method can greatly suppress the generation of crack defects during laser cladding. Attached Figure Description

[0008] Figure 1 This is a schematic diagram of a powder feeder; Figure 2 Schematic diagram of a four-way powder delivery nozzle; Among them: 1. Powder tube one; 2. Powder tube two; 3. Powder feeder one; 4. Powder feeder two; 5. Powder feeder three; 6. Powder feeder four. Detailed Implementation

[0009] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0010] In the process of large-area laser cladding, due to the multi-pass, multi-layer overlapping cladding process, and the difference in physical properties between the coating material and the substrate, in order to reduce the structural stress and thermal expansion differential stress at the interface between the coating and the substrate, control the occurrence of crack defects, and ensure the bonding performance and anti-stripping performance of the laser cladding impact-wear resistant coating with the titanium substrate, as well as the comprehensive performance such as wear resistance and impact resistance, the surface material of the laser cladding coating needs to have high hardness and high wear resistance, and the bottom material of the coating needs to be as close as possible to the titanium alloy substrate material to reduce the difference in mechanical properties and thermal expansion coefficient.

[0011] Therefore, this method is mainly based on the fact that the first layer of laser cladding is made of pure titanium alloy as a transition layer. Both the transition layer and the substrate are titanium alloys, which can reduce the thermal stress and structural stress between the coating and the substrate interface. At the same time, the transition layer can play a preheating role to reduce the temperature difference between the coating and the substrate interface, thereby reducing thermal stress, and improve the fluidity of the molten pool to a certain extent. This process method can greatly suppress the generation of crack defects during laser cladding.

[0012] The specific steps are as follows: (1) First, titanium alloy powder and hard particle reinforcing phase are conveyed to the powder feeding nozzle by a double-cylinder powder feeder, wherein powder cylinder one conveys titanium alloy powder and powder cylinder two conveys hard particle reinforcing phase.

[0013] (2) Then, titanium alloy powder + hard particle reinforcing phase is output through the powder feeding nozzle. Laser irradiation melts the titanium alloy powder and the thin layer on the substrate surface simultaneously, and after rapid solidification, a surface coating with extremely low dilution rate and metallurgical bonding with the substrate material is formed. At the same time, in order to ensure the uniformity of powder feeding, both titanium alloy powder and hard particle reinforcing phase are split into two at the powder feeding nozzle. That is, titanium alloy powder is output from powder feeding nozzles three and four, and hard particle reinforcing phase is output from powder feeding nozzles one and two.

[0014] (3) Secondly, when performing the first layer of laser cladding, only powder cylinder one is turned on. When performing the second layer and subsequent laser cladding, powder cylinder one and powder cylinder two are turned on at the same time. This can achieve the effect of cladding pure titanium alloy as a transition layer in the first layer of laser cladding, which plays a preheating role, reduces thermal stress and structural stress, improves the fluidity of the molten pool, and suppresses the generation of crack defects during laser cladding.

[0015] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for controlling crack defects in titanium alloy parts through laser cladding, characterized in that, Includes the following steps: Step 1: Titanium alloy powder and hard particle reinforcing phase are conveyed to the powder feeding nozzles through a dual-cylinder powder feeder. Powder cylinder one conveys titanium alloy powder, and powder cylinder two conveys hard particle reinforcing phase. Step 2: Titanium alloy powder + hard particle reinforcing phase is output through the powder feeding nozzle. Laser irradiation melts the titanium alloy powder and the thin layer on the substrate surface at the same time, and then solidifies rapidly to form a surface coating that is metallurgically bonded to the substrate material. Step 3: When performing the first layer of laser cladding, only powder cylinder one is turned on. When performing the second layer and subsequent laser cladding, powder cylinder one and powder cylinder two are turned on simultaneously. This allows the first layer of laser cladding to be clad only with pure titanium alloy as a transition layer, which serves as a preheating layer to reduce thermal stress and structural stress, improves the fluidity of the molten pool, and suppresses the generation of crack defects during laser cladding.

2. The laser cladding crack defect control process method for titanium alloy parts as described in claim 1, characterized in that, To ensure uniform powder feeding, both titanium alloy powder and hard particle reinforcing phase are split in two at the powder feeding nozzle and output through four powder feeding nozzles.

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