S.Z. Li

Wear behavior of a TiNi alloy

The wear behavior of a TiNi alloy after various heat treatments has been studied in three conditions: sliding wear, impact abrasion and sand-blasting erosion. The results show that for all three conditions, the TiNi in a pseudoplastic state shows much better wear resistance as compared with that in a pseudoelastic state. The wear resistance of a TiNi alloy is mainly dependent on the recoverable strain limit, i.e. the sum of the pseudoelastic and pseudoplastic strain limits.

Some developments for single-pass pendulum scratching

By using a single-pass pendulum impact scratch tester to study wear behavior of several commercial materials, some developments have been made for this testing technique. From the results, four criteria, i.e. specific energy e(=E/V), tangential dynamic hardness H-T(=F-T/A(T)), normal dynamic hardness H-N(=F-N/A(N)) and the scratching friction coefficient mu(=F-T/F-N), were obtained, where the specific energy and the tangential dynamic hardness presented a good linear relationship and were adopted as two equivalent measures of abrasion resistance of a material in single-pass pendulum scratching. The normal dynamic hardness H,corresponded well with the microhardness H-V, and could present wear properties of a material in abrasive wear with a steady load, instead of the microhardness. By comparison of single-pass pendulum scratching with sliding abrasion and sand-blasting erosion tests, it is found that the single-pass pendulum scratching is a form of impact abrasion between sliding abrasion and sand-blasting erosion, and more similar to the sand-blasting erosion with a low impingement angle.

A study of the corrosive wear of Ti-6Al-4V in acidic medium

Abstract The corrosive wear behaviour of Ti-6Al-4V was examined using a pin-on-disc wear device and potentiostat in 1N H 2 SO 4 at different polarized potentials. The morphology of the debris and wear scars was investigated using scanning electron microscopy and metallography. The hydrogen content in both the debris and the subsurface of the specimen was determined using the inert gas fusion method and secondary ion mass spectrometry respectively. The experiment shows that the wear losses may be partially controlled by cathodic protection but wear increases with over protection. The unusual wear losses can be explained by hydrogen embrittlement of the titanium alloy because of hydrogen evolution on the specimen surface.

Acceleration of corrosive wear of duplex stainless steel by chloride in 69% H3PO4 solution

Plots of corrosive wear loss with load and anodic polarization curves during friction were examined for duplex stainless steel (DSS) in 69% H2PO4 solution with or without Cl- by a pin-on-ring apparatus. Morphology of tracks and debris was observed in a scanning electron microscope. Variation of Vicker hardness of worn surface was also tested. The defects in wear subsurface were analysed by means of the positron annihilation technique (PAT) and a transmission electron microscope (TEM). The results show that the acceleration of chloride on corrosive wear of the steel is due to the brittle-fracture of the worn surface.

Evaluation of abradability of porous seal materials in a single-pendulum scratch device

The abradability of porous seal materials has been evaluated using a single-pendulum scratch device. The results shows that the specific energy e (= E/V) and the tangential dynamic hardness H(T)(= F(T)/A(T)) for small incursion depth are obviously higher than those for greater incursion. The specific energy e and tangential dynamic hardness H(T) have been proposed as two equivalent criteria of abradability of seal materials. The abradability of porous seal materials is dependent on both mechanical properties of the materials and extent of densification. A careful balance between them is the key to a satisfactory seal material.

Hydrogen-Induced Embrittlement Wear of a High-Strength, Low-Alloy Steel in an Acidic Environment

Abstract Corrosive wear of a high-strength, low-alloy steel (HSLA) was examined in 0.02 mol/L sulfuric acid (H2SO4) solution at different polarized potentials and loads using apin-on-disc wear devi...

Corrosion wear of duplex stainless steels in sulfuric acid solution containing chloride

Abstract The corrosion rate, wear rate, corrosion wear rate, variation of Vickers hardness of the worn surface, and the recovery time of passive film were determined for α + γ duplex stainless steel (DSS) in sulfuric acid (H2SO4) or H2SO4 + sodium chloride (NaCl) solution. In the chloride (Cl−) solution, the wear-induced corrosion and the corrosion-induced wear were ∼ 4% and 70% of the total damage, respectively. Damage was less in the absence of Cl−. Morphologies of tracks and debris also were observed. Results showed Cl− embrittled the worn surface of the metal.

Wear resistance of Ni-hard 4 and high-chromium cast iron re-evaluated

A comparison of the wear resistances of Ni-hard 4 and high-chromium (15-3) cast irons has been made under different testing conditions. Several kinds of wear tester were employed (reciprocating grooving tester, dry sand rubber wheel tester, single-pass pendulum impact grooving tester, and blasting erosion tester). The results show that whereas Ni-bard 4 seems to be more suitable to resist blasting erosion, high-chromium cast iron is better at resisting grooving wear, the ranking of materials changing with testing conditions. The measured wear resistance of the irons has been explained in terms of microstructure and hardness. Material removal occurred as a result of different mechanisms. For grooving wear, a harder metal surface is preferable, under blasting erosion conditions, material removal is mainly determined by the matrix.

Impact abrasive behavior of SiCp/2024Al composites in single pendulum scratch testing

Impact abrasive behavior of SiCp/2024Al composites has been investigated using a single pendulum scratch device. The results show that most of the composites exhibit better abrasive resistance than the unreinforced matrix alloy except the one containing 15 vol.% particles of 20 mu m in size. The impact abrasive resistance of the composites increases with decreasing particle size and increasing volume fraction. The matrix ahoy presents a thin softened layer immediately under the scratch bottom, succeeded by a hardened one for greater depth. The scratching process of the composites containing large particles was that the surface particles were compressed into a surface layer, shocked fragmentally or debonded from the matrix at interfaces, and finally pulled out. For composites containing small particles, the particles could coordinate with the matrix in deformation and were subjected together with the matrix to being ploughed, cut and finally removed.

Effect of fiber orientation on a graphite fiber composite in single pendulum scratching

Impact abrasive behavior of a graphite (T300)/polyamide composite was investigated by using a single pendulum scratching device. The results showed that the wear resistance of the composites decreased as the orientation angle beta between the fiber axis and the scratching direction increased; the friction coefficient decreased linearly as beta increased from 0 to 60 degrees, but increased as beta increased from 60 to 90 degrees. The scratching mechanism was analyzed by scanning electron microscopy, and the effect of the fiber orientation on wear and friction of the composite was explained in terms of ploughing, interface friction and breakage of fibers.