How can metal 3D printed parts improve their surface wear resistance?

一,Optimizing process parameters: preventing microstructural flaws at their origin
1. Cooperative management of scanning approach and laser power
The dynamic behaviour of the melt pool in the Selective Laser Melting (SLM) process is directly impacted by the alignment of laser power and scanning speed. For instance, when the laser power is 250W and the scanning speed is 1000mm/s, the melt pool can cool at a rate of 10 K/s, forming small strengthening precipitates of γ 'and γ' 'phases. This raises the surface hardness of the printed part to 450 HV, which is 30% higher than that of traditional castings. This is the case for Inconel 718, a nickel-based alloy. A checkerboard scanning approach, on the other hand, can efficiently distribute heat stress, diminish the density of surface cracks, and lessen the likelihood of peeling during wear.
2. Precise alignment of energy density and layer thickness
According to experimental data, the surface roughness of 316L stainless steel printed parts can be decreased from Ra 8.2 μ m to Ra 4.5 μ m when the layer thickness is decreased from 50 μ m to 30 μ m. The surface density of titanium alloy printed parts can approach 99.95% by combining the energy density formula (E=P/(v × h × t), where P is power, v is velocity, h is spot diameter, and t is layer thickness), and optimizing parameter combinations. This greatly reduces abrasive wear caused by pores.
3. Design innovation for supporting structures
Using tree-like supports rather than conventional grid supports for hanging structures can prevent surface damage during post-processing and reduce the contact area of supports by over 30%. Boeing's adaptive support method provides a high-quality substrate for a subsequent wear-resistant treatment by dynamically adjusting the support density to lower the surface defect rate of printed aviation engine blades to 0.3%.
Surface densification and microstructure reconstruction are two post-processing strengthening technologies.
Densification procedure using hot isostatic pressing (HIP)
HIP technology uses the combined effects of high pressure (100–150 MPa) and high temperature (1000–1200 °C) to remove almost 99% of the pores found in printed objects. Following HIP treatment, the rolling contact fatigue life was raised by 2.3 times and the surface hardness of turbine discs made of cobalt chromium alloy increased from 380 HV to 520 HV. Even in an atmosphere with temperatures as high as 1500 °C, the LEAP engine fuel nozzle treated by GE Aviation utilizing this technique retains consistent wear resistance.
二,Surface modification via Friction Stir Processing (FSP)
FSP can refine grain size to 0.5-1 μm by using high-speed rotating stirring heads to create plastic deformation. When compared to untreated components, FSP treatment can raise the surface hardness of printed aluminium alloy parts to 180 HV and boost wear resistance by 40%. For complex internal flow channel configurations, such as the wear-resistant treatment of cooling channels in aircraft thrusters, this technology is especially well-suited for surface strengthening.
LSP, or laser shock peening
LSP creates a residual compressive stress layer on the material surface up to 1 mm deep by using high-energy pulsed laser-induced plasma shock waves. Following LSP treatment, the fatigue wear life of printed parts made of TC4 titanium alloy was tripled and the surface microhardness rose to 520 HV. Key landing gear components of the C919 airplane have had their surfaces strengthened using this technology.
三,A multi-scale protection system is constructed using functional coating technology.
1. Hard coating using physical vapour deposition (PVD)
The friction coefficient can be lowered to 0.15 and the surface hardness of 316L stainless steel printed parts can approach 2200 HV by applying a CrN coating utilizing multi-arc ion plating technology. At a high temperature of 1000 °C, Siemens Energy decreased the oxidation wear rate of gas turbine blades by 80% as compared to the substrate material after applying TiAlN coating.
2. Gradient coating using laser cladding
Synchronous powder feeding laser cladding technology can be used to create FeCrAlY/YSZ gradient thermal barrier coatings on the surface of nickel-based alloys. At a high temperature of 1400 °C, the coating maintains a low thermal expansion coefficient of 0.5%, extending the thermal fatigue life of turbine blades in aviation engines to 2000 cycles-five times longer than that of uncoated parts.
3. Electroplating coating of nano composite
In comparison to pure nickel coatings, the hardness of the coating may be raised to 650 HV and its wear resistance can be improved by 60% by adding 0.5 weight percent nano SiC particles to the nickel-based electroplating solution. The service life of this technology has been increased to three years in sandy seawater settings, and it has been used to protect the surface of drilling pump shafts on offshore platforms.
四,Common use cases and performance evaluation
1. Turbine disc for aircraft engines
After 1000 hours of high-temperature wear testing, the Inconel 718 turbine disc made by Rolls-Royce utilizing the SLM+HIP+PVD composite process shown a notable improvement in surface roughness, increasing by only 0.2 μm as opposed to 0.8 μm for typical forged parts.
2. Deep-sea drilling platform gearbox
The SLM+FSP+laser cladding composite used to treat the 316L stainless steel gear created by CSIC raises the pitting potential to +0.3V (SCE) in a 3.5% NaCl solution and provides 2.5 times the wear resistance needed to meet API 6A standards.
3. Piston rings for automobile engines
At a high temperature of 200 °C, the friction coefficient of the steel-based piston ring produced by SLM is lowered to 0.08 and the fuel consumption rate is decreased by 3.2% following laser shock strengthening and diamond-like carbon (DLC) coating treatment.