Search

Zinc (Zn) and its alloys have been proved to be promising candidate materials for biodegradable cardiovascular stents. In this study, a novel extruded Zn-0.02 Mg-0.02Cu alloy was prepared. Compared with pure Zn, the Zn-based alloy showed higher mechanical properties, and the Zn-based alloy could significantly accelerate Zn2+ release, reaching 0.61 ± 0.11 μg/mL at 15 days of immersion. In vitro biocompatibility studies demonstrated that the Zn-based alloy had excellent cytocompatibility and hemocompatibility, including low hemolysis rate (0.63 ± 0.12%) and strong inhibitory effect on platelet adhesion. Subsequently, the Zn-based alloy stent was implanted into the left carotid arteries of New Zealand white rabbits for 12 months. All the rabbits survived without any adverse clinical events, and all the stented arteries were patent during the study period. Rapid endothelialization at 1 week of implantation was observed, suggesting a low cytotoxicity and thrombosis risk. The stent corroded slowly and no obvious intimal hyperplasia was observed for 6 months, after which corrosion accelerated at 12 months. In addition, no obvious thrombosis and systemic toxicity during implantation period were observed, indicating its potential as the backbone of biodegradable cardiovascular stents. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1814-1823, 2019.

PurposeThe objectives of this paper are to assess the sliding wear response of a zinc‐based alloy over a range of sliding speeds and pressures in oil‐lubricated condition with respect to a cast iron, to understand the role of different microconstituents in controlling the observed wear behaviour and to examine various operating material removal mechanisms.Design/methodology/approachSliding wear tests have been carried out using a pin‐on‐disc machine in oil‐lubricated condition at different speeds and pressures. The wear response has been explained in terms of specific nature of various microconstituents of the specimen materials and substantiated through the characteristics of wear surfaces, subsurface regions and debris particles.FindingsThe wear rate increased with the sliding speed while load produced a mixed influence. Further, the friction coefficient and frictional heating were influenced by the test duration, load and speed in a mixed manner. Moreover, the zinc‐based alloy attained lower wear rate but higher friction coefficient than that of the cast iron while frictional heating followed a mixed trend.Practical implicationsThe paper further establishes a zinc‐based alloy as a potential substitute material system to a well‐known cast iron in tribological applications and enables further understanding of the wear mechanisms.Originality/valueThe present paper assesses the sliding wear performance of a lighter zinc‐based alloy as an effective potential substitute material system to cast iron in tribological applications. An attempt has also been made to understand the role played by different microconstituents in controlling the wear behavior and substantiate the wear response through the characteristics of wear surfaces, subsurface regions and debris.

The microstructures characteristics of interface and wear resistance Of ZnAl27 composite reinforced by SiC particles have been studied by means of SEM and HRTEM. The results shown that SiC particles could be distributed in ZnAl27 alloy uniformly, and the excellent combined interface between SiC particles and ZA27 matrix is formed. CuZn4 could nucleate on SiC particles and grow up at higher speed along SiC particles than at the vertical direction. The wear resistance of the ZnAl27 alloy could be increased remarkably due to the addition of SiC particles. When the SiC particles are added to 30％, the wear resistance was raised by 126.5 times

This study pertains to the observations made during the sliding wear response of a zinc-based alloy in different test conditions. The effects of sliding speed and load on the wear behaviour of the alloy have been studied. The properties evaluated were wear rate, frictional heating and coefficient of friction. The wear performance of the zinc-based alloy has been compared with that of a conventional cast iron in identical test conditions. The wear rate of the samples increased with applied load and sliding speed while the seizure resistance (load) deteriorated with speed. The zinc-based alloy exhibited less wear rate and reduced frictional heating than that of the cast iron while friction coefficient followed a reverse trend. Observed wear response of the samples has been discussed in terms of specific features like lubricating, load carrying, microcracking and thermal stability of various microconstituents of the samples, and substantiated further through the features of wear surfaces, subsurface regions and debris.

This investigation presents the observations made pertaining to the lubricated sliding wear response of a zinc-based alloy containing nickel over a range of applied pressures and sliding speeds. Properties studied were wear rate and frictional heating. The varying wear response of the samples under different material and test conditions has been substantiated through the features of wear surfaces, subsurface regions, and debris. The role of various microconstituents in the material and their specific features have been correlated with the observed wear behaviour of the alloy in different material and test conditions. The wear rate and frictional heating increased with pressure and speed. The data plots in general comprised initially low slope followed by a higher slope at larger applied pressures. Heat-treated samples performed better than the as-cast one except at the maximum sliding speed; a reverse trend was noted in the latter case. The study suggests the benefits of heat treatment in terms of improved wear response of the alloy under specific test conditions. Moreover, the wear behaviour of the samples for different material and test conditions could be explained in terms of the features of their microconstituents and the predominance of one set of factors causing improved wear behaviour over the other producing a reverse effect.

This investigation deals with the observations made pertaining to the influence of the duration of heat treatment (ageing) on the sliding wear response of a zinc-based alloy. The heat treatment comprised of solutionizing followed by artificial ageing for different durations. Partially lubricated sliding wear tests were carried out at a fixed applied pressure, speed and distance. The heat-treated samples attained less strength and hardness but more elongation over the as-cast one. The wear rate and frictional heating initially decreased with increasing ageing duration. This was followed by the attainment of the minimum and then a reversal in the trend at longer durations of ageing. The tensile strength and hardness decreased with increasing duration of ageing and became stable beyond certain ageing period while elongation followed a reverse trend. The response of the samples has been substantiated through the fractographic features and characteristics of wear surfaces, subsurface regions and debris.

An attempt has been made in this investigation to assess the wear behavior of a zinc-based alloy in slurry. The influence of the sand content of the slurry and traversal speed and distance on the wear response of the alloy has been examined. Tests were also conducted in the liquid-only medium to assess the role played by the suspended sand particles in the medium. Testing the samples in the liquid-only medium (i.e., without sand particles) caused maximum wear rate. It was also observed that an intermediate sand concentration in the liquid exists wherein the samples experienced maximum wear rate (although less than in the liquid-only medium). Further, increasing the speed of rotation of the specimens in the liquid plus sand environments led to higher wear rate while the trend tended to reverse in the sand-free liquid environment. The alloy initially displayed increased wear rate with increasing traversal distance. This was followed by the attainment of the maximum, a decrease in the wear rate and then a steady state value at longer traversal distances. Wear behavior of the alloy under different experimental conditions was further substantiated through the features of the affected wear surfaces and subsurface regions (perpendicular below the affected surfaces).

Observations pertaining to the influence of microstructural alterations brought about through heat treatment on the sliding wear behaviour of a zinc based alloy comprising of silicon have been analysed in this study. The effects of sliding conditions such as pressure and speed on the wear response of the alloy in as cast and heat treated conditions have also been investigated. The as cast alloy revealed dendritic structure consisting of primary α, eutectoid α + η, and ϵ phase. Silicon was present in the alloy microstructure as discrete particles. Heat treatment caused breaking of the dendritic structure and more homogeneous distribution of various microconstituents without affecting the morphology and mode of distribution of the silicon particles. The heat treated alloy attained superior wear response as compared with the as cast one especially under more severe wear conditions. Wear rate versus pressure plots revealed two slopes wherein the slope was low at low pressures and increased considerabl...

This investigation deals with the observations made pertaining to the sliding wear behaviour of a zinc-based alloy containing nickel and silicon in partially lubricated condition. Wear tests were conducted over a range of applied pressures and sliding speeds. The effect of microstructural changes brought about through T6 heat treatment involving solutionizing followed by artificial ageing on wear behaviour was also investigated. The wear rate increased with pressure. The slope of the wear rate versus pressure plots was low initially up to a specific pressure. This was followed by a higher slope beyond the (specific) pressure. In some cases, the rate of change in wear rate, i.e. the slope, decreased at still higher pressures. Moreover, the (specific) pressure decreased with sliding speed in general. Increasing sliding speed caused the wear rate of the as-cast zinc-based alloy to increase up to a sliding speed of 2.68 m/s. The trend reversed at a still higher speed of 4.60 m/s. However, increasing wear rate with speed was noted for the heat-treated alloy over the entire speed range. Heat treatment led to reduced wear rate up to a sliding speed of 2.68 m/s. An opposite trend was observed at a higher speed of 4.60 m/s in this case. Specimen seizure was noted at speeds above 2.68 m/s in the case of the as-cast alloy whereas seizure took place only at 4.60 m/s for the heat-treated alloy samples. Frictional heating increased with pressure and speed. The specific response and changing mode of distribution of various phases were thought to be responsible for the typical wear behaviour of the alloy in specific material and test conditions. The predominance of parameters like thermal stability and cracking tendency over each other is suggested to lead to the varying wear behaviour of the alloy in different (material and sliding) conditions. The wear response of the samples has been substantiated through characteristics of their wear surfaces, subsurface regions and debris.

This study discusses the sliding wear response of a zinc-based alloy (conforming to ZA 27) in mixed lubrication conditions at different sliding pressures and speeds. A conventional bearing bronze (conforming to SAE 660) was also tested under identical test conditions for comparison purposes.Wear rate increased with speed and pressure. Further, the zinc-based alloy attained superior wear response (less wear rate and frictional heating) than the bronze at all test speeds except prior to seizure (occurring at 7.0 MPa) at the speed of 4.60 m/s. The trend reversed in the latter case. Wear rate of the specimens also agreed with the degree of frictional heating experienced by them. A higher wear rate corresponded to larger frictional heating and vice versa. Wear behaviour of the samples improved considerably in the present study due to the presence of the oil lubricant as compared to the study in dry conditions.Wear behaviour of the samples has been discussed in terms of the nature and response of their ...

This investigation deals with the observations made during the sliding wear behaviour of a zinc-based alloy in the as-cast and heat-treated conditions. Partially lubricated wear tests were conducted over a range of sliding speeds and applied pressures. Wear rate versus pressure plots assumed lower slope initially. This was followed by a larger slope at higher applied pressures. Increasing speed/pressure led to inferior wear response of the alloy. Also, specimen seizure was noticed only when sliding took place at high speeds. Interestingly, in spite of the deteriorating strength and hardness properties, the heat-treated alloy performed superior to that of the as-cast variety irrespective of the test condition except at the maximum speed of sliding. The trend reversed in the latter case. Wear behaviour of the samples has been further substantiated with the features of their wear surfaces, subsurface regions and debris particles.

The present paper deals with the dry sliding wear behaviour of a zinc-based alloy against a stainless steel (grade 304) disc (counterface). The performance of the zinc-based alloy has been compared with that of a conventionally used leaded-tin bronze under identical test conditions. Wear tests have been conducted over a range of pressure and speed. The results revealed that the zinc-based alloy performs better than the bronze over the entire range of speed and pressure. Further, the bronze attained improved wear response at the higher sliding speed. At the lower speed, material chipping off caused the tests to be stopped beyond a specific pressure in the case of the bronze, while material seizure was observed at the higher speed. The zinc-based alloy attained comparable wear rates at both the speeds, while seizure pressure reduced at the higher speed.

ZA22-Al 2 O 3 composites were prepared by means of a squeeze casting process. The effects of fibre volume friction ( V f ), applied load, time and fibre orientation on the dry friction and wear behaviour were studied. The results show that the wear resistance and the coefficient of friction of the composites increased with V p . The wear weight loss of the composite during wear testing increased with the applied load or the wearing time. The weight loss and the coefficient of friction were related to the fibre orientation. Both the weight loss and the coefficient of friction were smaller when fibres were normal to the friction surface than when fibres were parallel to it. The coefficient of friction decreased with load, and increased with time. An Fe-rich layer about 10 μm thick on the wear surface was found by means of scanning electron microscopy (SEM) and an energy spectrometer. The wear mode of the ZA22 alloy is mainly ploughing groove and adhesion, while the wear mode of the ZA22-Al 2 O 3 composite is mainly slight ploughing groove and oxidization.