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In this study, experimental analysis and finite element modeling (FEM) were employed to investigate the microstructure and mechanical properties of duplex coatings composed of a Cr 3 C 2 –NiCr interlayer and a top AlCrN film in comparison with these of a single AlCrN film. Results showed a significant improvement in the adhesive strength, load-bearing capacity, H/E, and H3/E2 ratios, and hardness of the AlCrN/Cr 3 C 2 –NiCr duplex coatings compared to the single AlCrN film, especially the wear resistance that increased by nearly eight times under heavy loads. Moreover, FEM analysis revealed that the duplex design reduced the stress concentration area on the surface of AlCrN film and kept it far away from the contact interface during load-bearing. [ABSTRACT FROM AUTHOR]

Tribological behaviors of three typical kinds of diamond‐like carbon (DLC) films (a‐C, a‐C:Cr, and a‐C:H) in sulfuric acid and sodium hydroxide solutions were investigated. The a‐C film showed the lowest stable coefficients of friction (COF) in both sulfuric acid and sodium hydroxide solutions but the worst wear resistance in sulfuric acid solution. The a‐C:H film showed the highest COF in sulfuric acid solution and the best wear resistance in both sulfuric acid and sodium hydroxide solutions. The a‐C:Cr film exhibited superior comprehensive tribological performance in sulfuric acid solution, while in sodium hydroxide solution, high COF and very poor wear resistance was observed. What is more, friction and wear mechanism was revealed by investigating the friction‐induced material evolutions on the sliding surface. [ABSTRACT FROM AUTHOR]

• Textured DLC films were in-situ deposited by masking substrate with metallic meshes. • Covered region became concave part while exposed region became protruding part. • In-situ surface texturing improved film hardness, elastic modulus and lipophilicity. • DLC-T52% reached the lowest COF and wear rate under dry and lubricated conditions. Surface texturing is emerging as one of the viable means that can be applied to improve the tribological properties of diamond like carbon (DLC) films. In this study, textured DLC films were in-situ fabricated by masking the substrate with metallic meshes during the deposition process. The tribological behaviors of the textured DLC films with micro-dimples densities of 39%, 52% and 58% were studied and compared with that of the un-textured DLC films under dry friction and liquid lubrication conditions. The results showed that the textured DLC films with micro-dimples density of 52% exhibited the lowest average coefficient of friction (COF) and wear rate both under dry friction and liquid lubrication conditions. The improved tribological performance of the textured DLC films with optimum micro-dimples density (52%) under dry friction could be attributed to the friction-induced graphitization of the textured layer and entrapment of wear debris in the micro-dimples. Under liquid lubrication condition, the micro-dimples played the double role of wear debris and lubricating oil reservoirs, then the graphitized textured layer on the worn surface combined with the liquid lubrication film formed a solid-liquid duplex lubricating, thus achieving significantly lower friction and wear. [ABSTRACT FROM AUTHOR]

Fe-based amorphous coating is deposited on invar steel substrates using detonation spray and then through the cryogenic cycling (CCT) treatment from 0 to 60 cycles with the interval 10 cycles. Effects of CCT on microstructure, thermal properties, mechanical and tribological properties were investigated. It was found that, all the coated samples with CCT are still well bonded with the invar steel substrate, except for the surface of C60 appears local cracks. Moreover, it also found that although CCT did not significantly change the phase structure of the amorphous coating, CCT promoted the rejuvenation behavior in the amorphous coating, which also led to the heterogeneity of the internal structure. Attributed to this heterogeneity, it promotes the generation of a large amount of free volume in the amorphous coating, which results in a significant change in the toughness and resistance to crack propagation of the amorphous coating. And after 50 CCT cycles, the amorphous coating has undergone an obvious ductile-brittle transition, which has the highest fracture toughness K IC and plastic work W p value. The COF and wear rate of coatings increased initially, then followed by a decrease, but then again increased with the increase of CCT cycles. The 50-cycles coatings exhibited the lowest COF (0.60) and wear rate (0.56 × 10−5 mm3N−1 m−1). The wear mechanism of all the samples is mainly delamination wear with oxidative wear, but the degree of delamination wear is obviously different, showing a trend corresponding to the tribological behavior of the amorphous coating. Therefore, the CCT method could be an effectively strategy to ameliorate the toughness and then enhance the wear performance of the Fe-based amorphous coating. • Fe-based amorphous coatings were deposited by detonation spraying. • The coated samples were treated by cryogenic thermal cycling from 0– 60 cycles. • The cryogenic thermal cycling treated samples undergo a brittle-tough transition. • C50 coatings exhibit the best friction and wear properties. [ABSTRACT FROM AUTHOR]

Duplex coating, composing of a thick Cr 3 C 2 -NiCr interlayer and a top CrN film, were deposited by high velocity oxy-fuel (HVOF) and arc ion plating technologies, and the microstructure, mechanical properties and thermal shock resistance of the duplex coating were investigated compared to those of the single CrN film, as well as tribological behaviors at elevated temperatures. Results showed that the duplex coating exhibited high surface hardness, H / E and H 3/ E 2 ratios, load-bearing capacity and adhesive strength due to the supporting of the Cr 3 C 2 -NiCr interlayer, which contributed to improve the wear properties of duplex coating sliding against Al 2 O 3 ball. At 25 °C, the duplex coating had a higher friction coefficient and a relatively low wear loss, and the main wear mechanism was abrasive wear. As the temperature increased to 350 °C, the top CrN film of duplex coating was worn out totally. The severe mismatch of coefficient of thermal expansion (CTE) between Cr 3 C 2 -NiCr interlayer and substrate that might have a negative impact on wear resistance of duplex coating at high temperature. In addition, a large number of debris produced due to oxidation peeling of the coatings were compacted to form a thick transfer film during the sliding process, resulting in badly adhesive wear. The wear mechanisms were adhesive and oxidation wear accompanied with abrasive wear at high temperature (from 150 °C to 550 °C). • The CrN/Cr 3 C 2 -NiCr duplex coatings are fabricated by PVD/HVOF. • Duplex coatings show superior mechanical properties than single PVD film. • Cr 3 C 2 -NiCr interlayer significantly improves wear resistance of CrN film at 25 °C. • Mismatch of CTE in duplex coating and friction induced oxidation results in severe wear above 150 °C. [ABSTRACT FROM AUTHOR]