Role of phase transition in the unusual microwear behavior of superelastic NiTi shape memory alloy

The excellent microwear performance of nano-grained superelastic nickel titanium (NiTi) polycrystalline shape memory alloy (SMA) is reported in this paper. The microwear test was conducted at temperatures ranging from 22 to 120 °C by a Hysitron triboindenter. The results showed that the NiTi SMA has superior microwear resistance compared to traditional tribo-materials such as stainless steel AISI 304 and that the material exhibits unusual hardness dependence of wear within certain temperature regimes. With the increase in temperature from 22 to 120 °C, wear resistance was found to decrease anomalously with an increase in hardness. Further investigation and analysis confirmed that the stress-induced phase transition during contact and wear play an essential role in the material's high wear resistance. It is demonstrated through contact mechanics analysis that the increase of hardness with temperature was mainly due to the increase in the phase transition stress. The observed applied threshold load that corresponds to the onset of the plastic deformation in the contact area was strongly influenced by the phase transition process at the tip region. For the investigated superelastic NiTi, the temperature-dependent interplay between reversible phase transition and irreversible plastic yielding plays a key role in the temperature dependence of the wear performance and is responsible for the observed apparent unusual hardness–wear relationships.     

On the Deformation of Superelastic TiNi Alloy

Superelastic properties of TiNi alloy have made it a potential candidate for high wear resistance applications. Unfortunately, deformation and wear behavior of superelastic TiNi is not well-understood and more work is needed to fully exploit its wear properties for tribological applications. In the present study, an attempt is made to identify factors affecting the deformation and wear of superelastic TiNi and compare to stainless steel through a series of sliding wear, scratch, and indentation experiments.     

Tribological Behavior of New Martensitic Stainless Steels Using Scratch and Dry Wear Test

This paper focuses on the tribological characterization of new martensitic stainless steels by two different tribological methods (scratch and dry wear tests) and their comparison to the austenitic standard stainless steel AISI 316L. The scratch test allows obtaining critical loads, scratch friction coefficients, scratch hardness and specific scratch wear rate, and the dry wear test to quantify wear volumes. The damage has been studied by ex situ scanning electron microscopy. Wear resistance was related to the hardness and the microstructure of the studied materials, where martensitic stainless steels exhibit higher scratch wear resistance than the austenitic one, but higher hardness of the martensitic alloys did not give better scratch resistance when comparing with themselves. It has been proved it is possible to evaluate the scratch wear resistance of bulk stainless steels using scratch test. The austenitic material presented lower wear volume than the martensitic ones after the dry wear test due to phase transformation and the hardening during sliding.     

Effect of nitrogen on the corrosion-erosion synergism in an austenitic stainless steel

High temperature gas nitrided AISI 304L austenitic stainless steel containing 0.55 wt% N in solid solution, was corrosion, erosion and corrosion-erosion tested in a jet-like device, using slurry composed of 3.5% NaCl and quartz particles. Scanning electron microscopy analysis of the damaged surfaces, mass loss measurements and electrochemical test results were used to understand the effect of nitrogen on the degradation mechanisms. Increasing the nitrogen content improved the corrosion, erosion and corrosion-erosion resistance of the AISI 304L austenitic stainless steel. Smoother wear mark contours observed on the nitrided surfaces indicate a positive effect of nitrogen on the reduction of the corrosion-erosion synergism.     

Laser composite surfacing of AISI 304 stainless steel with titanium boride for improved wear resistance

The present study concerns development of a hard in situ boride-dispersed composite layer on the surface of AISI 304 stainless steel substrate to improve the wear resistance property. Laser processing was carried out by melting the surface of sand-blasted AISI 304 stainless steel substrate using a continuous wave CO₂ laser and simultaneous deposition of a mixture of K₂TiF₆ (potassium titanium hexafluoride) and KBF₆ (potassium hexafloroborate) (in the weight ratio of 2:1) using Ar as shrouding environment. Powder feed rate was maintained constant at 4 g/min. Irradiation results in dissociation of a pre-deposited mixture along with a part of the stainless steel substrate, intermixing and rapid solidification to form the composite layer on the surface. The micro-structure of composite layer consists of dispersion of titanium boride particles in AISI 304 stainless steel matrix. Volume fraction of particles is found to be uniform throughout the composite layer, though varied with laser parameters. The micro-hardness of the surface was improved 250–350 VHN as compared to 220 VHN of the AISI 304 stainless steel substrate with a significant improvement in wear resistance property. The mechanism of wear was found to be a combination of adhesive and abrasive in as-received stainless steel. However, it was predominantly abrasive for laser composite surfaced stainless steel.     

Wear and corrosion wear of medium carbon steel and 304 stainless steel

Wear and corrosive wear involve mechanical and chemical mechanisms and the combination of these mechanisms often results in significant mutual effects. In this paper, tribological behavior, X-ray peak broadening, and microstructure changes of carbon steel AISI 1045 and stainless steel AISI 304 samples under simultaneous wear and corrosion were investigated and the results were compared with those obtained from dry wear tests. 3.5 wt.% NaCl solution was used as the corrosion agent and a pin-on-disk tribometer was employed to perform wear and corrosive wear tests.X-ray diffraction measurements have shown that by increasing the applied load, the worn surfaces of carbon steel samples reached a constant strain at which fracture and wear occurred. Whereas in 304 stainless steel samples, by increasing the applied load, broadening of X-ray diffraction peaks was decreased.Wear tests of carbon steel and stainless steel samples have shown smaller weight losses and lower friction coefficient in the presence of corrosive environment. Study of worn surfaces suggested that depending on wear environment and applied load, different features of wear mechanisms were involved.     

Comparative Study of Wear Behaviors of a Selected Titanium Alloy and AISI H13 Steel as a Function of Temperature and Load

A comparative study of the wear behaviors of a selected titanium alloy and AISI H13 steel as a function of temperature and load was performed on a high-temperature wear tester. The titanium alloy and H13 steel presented totally different wear behaviors with the variation in temperature and load. Their behaviors are suggested to be attributed to the protective ability of tribo-oxides and the thermal softening resistance of the matrix. Compared to H13 steel, the titanium alloy presented poor room-temperature wear resistance, excellent high-temperature wear resistance, and an extremely protective function of tribo-oxides.     

Strain Hardening: Can it Affect Abrasion Resistance?

It has been largely reported in the literature that previous strain hardening has none or negligible effect on abrasive wear resistance. Those results are mainly obtained using sand rubber wheel tests and pin-on-disk tests, and have been attributed to the large strain hardening promoted by the abrasion phenomena themselves. The stresses involved in those tests are very high and the stress distributions spread toward subsurface regions at large depths. This work investigates the effects of strain hardening on low-severity (low stress at low depth) abrasive wear resistance. Microabrasion tests, normally regarded as lower stress tests, were used in order to impose low severity. Two types of stainless steels were tested: an austenitic AISI 304 steel and a ferritic AISI 430 steel. Strain hardening was obtained via thickness reduction (20%) of stainless steel sheets in a laboratory cold rolling mill. The microabrasion wear tests were carried out in a fixed-ball microabrasion tester with a three-axis load cell to continuously and simultaneously monitor the forces involved in the tests. Contrary to many findings so far in the literature, previous strain hardening increased abrasion wear resistance (55 and 63%, respectively) for both materials. Hertz calculations, simulations using Finite Element Program with explicit solution, conventional mechanical tests, microhardness profiles, microstructural analysis, and X-ray diffraction analysis were used to explain this paradigm shift for the case of microabrasion tests.     

AISI 304不锈钢的车削加工

针对AISI 304奥氏体不锈钢的特点,分析了AISI 304不锈钢材料的物理性能和切削加工性能,从刀具材料、切削用量和冷却液的选择等方面研究了AISI 304不锈钢车削加工的影响因素,通过合理选择和优化相关参数等方法有效解决了AISI 304不锈钢的加工难题,获得了较好的车削加工效果,提高了生产效率。     

基于多微凸体有限元分析的超弹TiNi合金磨损机制

对三种不同超弹性的TiNi合金及20MnV钢表面多微凸体在法向栽荷作用下的模型进行了有限元分析，并对超弹TiNi合金的磨损机制进行了探讨。结果表明，由于TiNi合金具有较高的最大弹性变形量，在相同栽荷下，表面上参加接触的微凸体数目随着超弹性的增加而增多,产生的弹性接触面积及最大Mises弹性应变要明显大于20MnV；塑性接触面积及最大Mises塑性应变相对减小。弹性变形能力的增强和塑性应变的减小可以使TiNi合金缓解外部的冲击并能够在磨损过程中抵抗较多的循环栽荷，从而表现出良好的耐磨性。     

马氏体相变温度对NiTi形状记忆合金抗磨损性能的影响

为了弄清楚N iTi形状记忆合金相与磨损性能之间的关系以及合金的磨损特征,研究了6种N iTi合金在相同条件下马氏体相变温度对磨损量的影响。结果表明:合金在没有发生永久性损坏带来的磨损的情况下,热弹性马氏体的转变,马氏体片的重新取向、合并及阻尼效应都能提高合金适应大变形量的能力,所以在粘着磨损过程中,弹性变形就会累积;对于6种合金来说,抗磨损性能主要取决于Ms转变温度,N i原子的析出和合金的硬度对合金的抗磨损性能也有显著影响。     

Effect of Silicon Nitride Ball on Adhesive Wear of Martensitic Stainless Steel Pyrowear 675 and AISI M-50 Races with Type II Ester Oil

Advanced bearing materials for future military and commercial gas turbines are required to operate at high speeds, high temperature, and higher thrust loads. At elevated operating conditions, the bearing and gear materials must be able to operate with ultrathin oil films without suffering detrimental effects of adhesive wear. The development of materials with rolling-element fatigue and corrosion resistance properties without deterioration in adhesive wear attributes is a significant challenge. To meet those performance requirements, the forerunner, martensitic stainless steel Pyrowear 675 (AMS 5930), has been in development for aerospace bearing and gear applications. This article addresses the adhesive wear performance of three variants of Pyrowear 675 with silicon nitride ball material simulating a hybrid bearing evaluated using a WAM8 machine. Baseline testing was conducted using conventional bearing steel AISI M-50. Adhesive wear testing was conducted at a temperature of 200°C and at different contact slips (15, 30, 50, and 70%) and entraining velocities (1.3 to 10.2 m/s). Posttest specimens were analyzed by scanning electron microscopy (SEM) and auger electron spectroscopy (AES). All the hybrid material pairs demonstrated very good adhesive wear performance compared to the baseline AISI M-50–AISI M-50 pair.     

Tribocorrosion behavior of Ni-17.5Si-29.3Cr alloy in sulfuric acid solution

The tribocorrosion property of a Ni-17.5Si-29.3Cr alloy against a Si₃N₄ ball was studied in comparison with AISI321 stainless steel using a ball-on-disk reciprocating tribotester in 1 M sulfuric acid (H₂SO₄) solution. The effects of load and sliding speed on the tribocorrosion properties of the alloy were investigated. The results indicated that the wear rate of the alloy increased while the friction coefficient decreased with increasing load. The wear rate of the alloy increased linearly with increasing sliding speed and the friction coefficient increased in the initial stages and then remained constant with increasing sliding speed. The wear mechanisms were mainly microploughing, uniform corrosion and pitting corrosion. Under the experimental conditions of the present study, the Ni-17.5Si-29.3Cr alloy showed excellent corrosion-resistence and anti-wear ability compared with AISI321 stainless steel.     

On the Tribocorrosion Responses of Two Stainless Steels

Tribocorrosion has considerable effects on AISI 304L used in olive processing equipment. In fact, some investigations have been conducted to compare the tribocorrosion behavior of AISI 304L to UNS 2205 stainless steels sliding against alumina in olive pomace–tap water filtrate. The active and passive surface states involved in tribocorrosion mechanisms of the steels have accordingly been analyzed. Mechanical and corrosion wear components were quantified. It was revealed that the tribocorrosion mechanism was dominated by mechanical removal. The mechanical resistance of UNS 2205 proved to be more important than that of AISI 304L. Furthermore, UNS 2205 was more sensitive to corrosion under sliding than AISI 304L due to its two-phase microstructure.     

加载速率对超弹性TiNi形状记忆合金棒材力学行为的影响

通过超弹性TiNi形状记忆合金棒材在不同加载速率下的力学性能试验,以相变应力、弹性模量、残余应变、耗能能力等作为该合金棒材的超弹性特征参数,分析了这些特征参数与加载速率的相关性。结果表明:该合金棒材在静态和非静态条件下的室温超弹性能存在一定差异。     

Fretting wear behavior of superelastic nickel titanium shape memory alloy

The fretting behavior of superelastic nickel titanium (NiTi) shape memory alloy was studied at various displacement amplitudes on a serve-hydraulic dynamic test machine. The results showed that the superelastic properties of the material played a key role in the observed excellent fretting behavior of NiTi alloy. Due to the low phase transition stress (only 1/4 the value of its plastic yield stress) and the large recoverable phase transition strain (5%) of NiTi, the friction force of NiTi/GCr15 stainless steel pair is smaller than the value of GCr15/GCr15 pair and at the same time the Rabinowicz wear coefficient of NiTi plate is about 1/9 the value of GCr15 plate under the same fretting conditions. For NiTi/GCr15 pair, even NiTi has a much lower hardness than GCr15, the superelastic NiTi alloy exhibits superior fretting wear property than GCr15 steel. It was found that the weak ploughing was the main wear mechanism of NiTi alloy in the partial slip regime. While in the mixed regime and gross slip regime, the wear of NiTi was mainly caused by the abrasive wear of the GCr15 debris in the three-body wear mode.     

Investigation of mechanical properties of friction-welded AISI 304 with AISI 1021 dissimilar steels

Austenitic stainless steel and low alloy steels are extensively used in various automotive, aerospace, nuclear, chemical, and other general purpose applications. Joining of dissimilar metals is one of the challenging tasks and most essential need of the present-day industry. It has been observed that a wide range of dissimilar materials can be easily integrated by friction welding. The objectives of the present investigation were obtaining weldments between austenitic stainless steel (AISI 304) with low alloy steel (AISI 1021) and optimizing the friction welding parameters in order to establish the weld quality. In the present study, an experimental setup was designed in order to achieve friction welding of plastically deformed austenitic stainless steel and low alloy steel. AISI 304 and AISI 1021 steels were welded by friction welding using five different axial pressures at 1,430 rpm. The joining performances of friction-welded dissimilar joints were studied, and influences of these process parameters on the mechanical properties of the friction-welded joints were estimated. The joint strength was determined with tensile testing, and the fracture behavior was examined by scanning electron microscopy (SEM) and was supported and backed by energy dispersive spectroscopy (EDS) analysis. Furthermore, the proposed joints were tested for impact strength, and the microhardness across the joint was also evaluated.     

Oil-Lubricated Fretting Behaviors of 304 Stainless Steels under Different Fretting Strokes and Normal Loads

The influence of oil lubrication on the fretting wear behaviors of 304 stainless steel flat specimens under different fretting strokes and normal loads has been investigated. The results proved that fretting regimes and fretting wear behaviors of 304 stainless steels were closely related to the fretting conditions. In general, the increase in normal load could increase wear damage during sliding wear. However, according to the results, a significant reduction in wear volume and increase in friction coefficient was observed when the normal load was increased to critical values of 40 and 50 N at a fretting stroke of 50 μm due to the transformation of the fretting regime from a gross slip regime to partial slip regime. Only when the fretting stroke further increased to a higher value of 70 μm at 50 N, fretting could enter the gross slip regime. There was low wear volume and a high friction coefficient when fretting was in the partial slip regime, because oil penetration was poor. The wear mechanisms were fatigue damage and plastic deformation. There was high wear volume and low friction coefficient when fretting was in the gross slip regime, because the oil could penetrate into the contact surfaces. Unlike the wear mechanisms in the partial slip regime, fretting damage of 304 stainless steels was mainly caused by abrasive wear in the gross slip regime.     

Steel machining chips as reinforcements to improve sliding wear resistance of metal alloys: Study of a model Zn-based alloy system

Two new steel-reinforced, metal-matrix composites (MMCs), Kirksite+1080 and Kirksite+M2 are developed by adding 25 wt% of AISI 1080/AISI M2 steel machining chips to a zinc-based alloy, Kirksite (4% Al and 3% Cu). The sliding wear resistance of the Zn alloy and the two MMCs, against AISI 52100 steel, is determined under increasing normal load (1–10 N) and temperature (25–150 °C), using a pin-on-disc configuration. The MMCs are found to exhibit superior wear performance under all test conditions. At room temperature, a maximum wear reduction in excess of 70% is obtained for the composites relative to the Zn-alloy at the highest load of 10 N. This reduction is as much as 86% at 150 °C and 1 N for the Kirksite+M2. The wear-reducing ability of the steel reinforcements is generally greater at the more severe contact conditions. The stability of the MMC matrices and recommended limits to the MMC operating temperatures are established using deformation measurements made via dynamic mechanical analysis. The principal wear mechanisms are analysed based on the sliding wear measurements, complemented by optical microscopy and SEM observations, and EDX microanalysis. The results show that the steel chip reinforcements are effective in improving the wear resistance of Zn alloys under severe conditions. Implications for use of low-cost machining chips as reinforcements to create MMCs for improved wear performance, and for recycling/reuse of these chips in advanced structural material systems are discussed.     

Tribological Behavior of Tin-Based Babbitt Alloy Lubricated by Seawater

In this article, the tribological behaviors of tin-based Babbitt alloy ZChSnSb 8–8 sliding against AISI 302 stainless steel lubricated by seawater were investigated. The results indicated that the friction coefficient decreases with increasing load and sliding speed, and the wear rate increases slightly with load but decreases with sliding speed. The low friction coefficient and wear rate are attributed to the unique “concrete structure” and seawater. As a lubrication medium, seawater has lubricating, cooling, and corrosive effects on the sliding couple.