image: Interface friction
Credit: Qianqian Cheng and Jie Jin form Tsinghua University.
Research teams from Tsinghua University and Anhui University of Technology have developed a novel post-processing technique using hot isostatic pressing (HIP) to improve the microstructure and wear resistance of titanium alloy surfaces. Through a careful combination of temperature and pressure, the team achieved remarkable reductions in residual stress-up to eightfold-and enhanced mechanical properties, including increased hardness and ductility. This fabrication process promotes better phase stability and interfacial bonding, enabling the coated titanium components to withstand extreme temperatures and harsh environments more effectively. This technology effectively overcomes the long-standing challenge of poor wear resistance in titanium alloys, offering a solid theoretical foundation and valuable technical guidance for the laser in-situ fabrication of TiN/Ti composite surface modification layers. The outcomes of this work hold significant potential to transform industries such as aerospace, biomedical implants, and industrial tooling—paving the way for more durable, reliable, and high-performance titanium-based components.
Titanium alloys are widely used in critical fields such as aerospace, marine engineering, and biomedical applications due to their excellent strength-to-weight ratio and corrosion resistance. However, their inherent wear resistance limitations (wear rate approximately ×10⁻⁴ mm³N⁻¹m⁻¹) severely restrict their application scope in sliding contact and abrasive environments. While conventional laser surface modification techniques can produce cermet composite coatings, the ultra-rapid cooling during laser processing (10⁶-10⁸ K/s) generates numerous metastable phases, high-density dislocations, and residual stresses in non-equilibrium microstructures, limiting performance enhancement effects. Existing technologies lack effective post-processing methods to eliminate these structural defects. Although traditional heat treatment can relieve stress, it is accompanied by ceramic phase coarsening and decreased interfacial bonding strength, making it difficult to achieve structural optimization while maintaining strengthening effects, becoming a key bottleneck restricting industrial applications.
The Solution: A multidisciplinary research team from Tsinghua University and Anhui University of Technology has incorporated hot isostatic pressing (HIP) technology into the post-processing of laser in-situ prepared TiN/Ti composite materials. The core innovation lies in harnessing the synergistic effects of temperature and static pressure within the HIP process. At 900°C and 150 MPa, the high-temperature environment activates atomic diffusion, facilitating phase transformation and precipitation behaviors. Simultaneously, the uniform static pressure not only accelerates diffusion kinetics but also effectively eliminates high residual tensile stresses formed during laser processing by applying uniform compressive stress.
X-ray diffraction and transmission electron microscopy analysis revealed the microscopic mechanisms: HIP treatment induced transformation of metastable needle-like α′-Ti martensite and dislocation cell structures into thermodynamically stable homogenized α-Ti and β-Ti phases, eliminating dislocation cell structures. Meanwhile, supersaturated nitrogen atoms precipitated through diffusion to form nanoscale tetragonal secondary TiN particles, providing effective dispersion strengthening and improving hardness, reducing residual stress by approximately 8 times. Simultaneously, the original TiN/Ti interface stacking faults and defective structures were replaced by a reconstructed amorphous transition layer approximately 1 nanometer thick. This interface structure possesses higher bonding strength and crack resistance capability. Based on these microstructural changes, synergistic effects of strength and toughness were achieved, resulting in approximately 25% improvement in wear resistance at 25°C and about 3.6 times improvement at 500°C, attributed to TiN phase friction retention and robust friction glaze layers.
The Future: This research pioneered the introduction of HIP technology into post-processing of laser in-situ prepared TiN/Ti ceramic modification layers, creating new directions for technological applications. The study systematically revealed phase transformation mechanisms, diffusion behaviors, and interface reconstruction patterns during HIP treatment, providing experimental evidence and theoretical support for deep understanding of physical mechanisms in post-processing of laser-prepared composite materials. This research confirmed that precise control of phase transformation and interface structural changes can achieve synergistic enhancement of material strength and toughness, providing a technical pathway for transitioning titanium alloy surface modification technology from laboratory research to industrial applications. The research results not only provide practical and effective solutions for addressing the long-standing technical problem of insufficient wear resistance in titanium alloys that has troubled the engineering community, but also offer new development concepts for complete surface modification technology systems from in-situ laser processing to post-processing, while providing important methodological references and technical insights for the development and optimization of other ceramic-metal composite material systems.
The Impact: This research pioneered the use of hot isostatic pressing technology for post-processing of laser-prepared composite materials. Through synergistic effects of temperature and pressure inducing phase transformation, interface reconstruction, and dislocation elimination, it established simultaneous enhancement of material strength and plasticity, thereby achieving significant improvement in wear resistance performance across a wide temperature range.
The research has been recently published in the online edition of Materials Futures, an international journal in the field of interdisciplinary materials science research.
Reference: Qianqian Cheng, Jie Jin, Jun Zheng. HIP-driven microstructural evolution in TiN/Ti cermet-modified layers enhances wide temperature range wear resistance[J]. Materials Futures, 2025, 4(4): 045002. DOI: 10.1088/2752-5724/adf4fa