The reach of tribology has expanded in diverse fields and tribology related research activities have seen immense growth during the last decade. This review takes stock of the recent advances in research pertaining to different aspects of tribology within the last 2 to 3 years. Different aspects of tribology that have been reviewed including lubrication, wear and surface engineering, biotribology, high temperature tribology, and computational tribology. This review attempts to highlight recent research and also presents future outlook pertaining to these aspects. It may however be noted that there are limitations of this review. One of the most important of these is that tribology being a highly multidisciplinary field, the research results are widely spread across various disciplines and there can be omissions because of this. Secondly, the topics dealt with in the field of tribology include only some of the salient topics (such as lubrication, wear, surface engineering, biotribology, high temperature tribology, and computational tribology) but there are many more aspects of tribology that have not been covered in this review. Despite these limitations it is hoped that such a review will bring the most recent salient research in focus and will be beneficial for the growing community of tribology researchers.

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A review of recent advances in tribology

Research and progress of laser cladding on engineering alloys: A review

The electrodeposition of composite coatings: Diversity, applications and challenges

In this work, we show that selective laser melting (SLM), apart from producing complex structures, can also act as a metallurgical method to modify the Ni/Ti ratio of NiTi shape memory alloys, and thus providing a feasible approach to tailor the transformation temperatures and to modify the mechanical performance of NiTi alloys. NiTi samples were fabricated by SLM with a large variation of process parameters, e.g. scanning speed (v) from 400 to 1200 mm s−1, hatch spacing (h) from 40 to 110 μm, and laser power (P) from 60 to 200 W. It is found that the martensite transformation temperature changes monotonously with the respective change of v, h or P. The composition analysis suggests that the different amount of Ni-loss under various SLM process conditions is the main reason for the evolution of transformation temperatures. Most importantly, good mechanical (total elongation >10 %) and functional properties under tensile mode have been obtained despite of the large variation of SLM process parameters and the presence of extensive defects. The good tensile properties and tailorable phase transformation temperatures will provide great potential to make novel NiTi smart structures.

Effect of process parameters on the phase transformation behavior and tensile properties of NiTi shape memory alloys fabricated by selective laser melting

A review on laser cladding of high-entropy alloys, their recent trends and potential applications

Design and characterization of FeCrCoAlMn0.5Mo0.1 high-entropy alloy coating by ultrasonic assisted laser cladding

In this work, a novel Ni1.5CrCoFe0.5Mo0.1Nb0.68 eutectic HEA coating with nano-lamellar microstructure was successfully designed by binary eutectic compositions strategy, thermodynamic calculation and simple experimental approach. Compared with the predicted eutectic compositions, the actual eutectic composition had a higher Nb content due to the increased solid solubility of Nb in the FCC phase. The Ni1.5CrCoFe0.5Mo0.1Nbx (x = 0.55 hypoeutectic, 0.68 eutectic, 0.8 hypereutectic) HEA coatings were prepared by laser cladding, which were composed of FCC phase with lattice parameter of a = ~3.59 A and Laves phase with lattice parameter of a = b = ~4.82 A and c = ~7.80 A. The FCC phase was enriched in Ni, Cr, Co and Fe elements, while the Laves phase was enriched in Nb and Mo elements. Typical eutectic lamellar and hypoeutectic/hypereutectic microstructures were obtained at the central regions, while the columnar crystals formed at the interfacial regions. The average micro-hardness of Nb0.55, Nb0.68 and Nb0.8 coatings were calculated as ~573.5 HV, ~665.8 HV and ~715.6 HV respectively. From x = 0.55 to x = 0.8, the wear resistance of Ni1.5CrCoFe0.5Mo0.1Nbx HEA coatings are increased, and the dominant wear mechanism of the HEA coatings transforms from adhesive wear to abrasive wear.

In-situ synthesis of nano-lamellar Ni1.5CrCoFe0.5Mo0.1Nbx eutectic high-entropy alloy coatings by laser cladding: Alloy design and microstructure evolution

Corrosion and tribo-corrosion behaviors of nano-lamellar Ni1.5CrCoFe0.5Mo0.1Nbx eutectic high-entropy alloy coatings: The role of dual-phase microstructure

Grain morphology control is a challenging issue for additive manufactured NiTi alloy, which directly affects the functional properties. In this work, La2O3 addition was applied to control microstructure and improve functional properties of directed energy deposited (DED) NiTi alloy. The results showed that the DEDed NiTi alloy mainly consisted of NiTi (B2) columnar grains and some coarse NiTi2 phases within and at the boundaries of NiTi grains. The addition of La2O3 led to the promotion of columnar-to-equiaxed transition and grain refinement of NiTi (B2) phase. La2O3 and LaNi secondary phases can be found in the DEDed NiTi alloy with La2O3 addition. The La2O3 precipitate could act as the effective heterogeneous nucleation site and the NiTi2 or LaNi precipitates could pin the grain boundaries contributing to the grain refinement and the formation of equiaxed grains of NiTi(B2) phase. The introduction of La2O3 could also refine the phase size and adjust morphology of NiTi2 phase, which was attributed to the increase of nucleation sites and more dispersed L(Ti-rich).The temperatures and latent heat of phase transformation evidently increase with La2O3 addition due to the decrease in the Ni content and La dissolved into NiTi(B2) phase. Improved superelasticity property was achieved after La2O3 addition owing to the promotion of grain order and yield strength of NiTi(B2) phase and the reduction of resistance from NiTi2 phase for the interface movement.

Yongchao Fang

Papers

Design and characterization of FeCrCoAlMn0.5Mo0.1 high-entropy alloy coating by ultrasonic assisted laser cladding

In-situ synthesis of nano-lamellar Ni1.5CrCoFe0.5Mo0.1Nbx eutectic high-entropy alloy coatings by laser cladding: Alloy design and microstructure evolution

Corrosion and tribo-corrosion behaviors of nano-lamellar Ni1.5CrCoFe0.5Mo0.1Nbx eutectic high-entropy alloy coatings: The role of dual-phase microstructure

Promoting the heterogeneous nucleation and the functional properties of directed energy deposited NiTi alloy by addition of La2O3

Influence of SiC fiber on thermal cycling lifetime of SiC fibers /YSZ thermal barrier coatings by atmospheric plasma spraying