Wear resistance and microstructure of Zn-Al-Si and Zn-Al-Cu alloys

Two Zn-Al-based ternary alloys containing 2 and 5 wt.% Si and one containing 5 wt.% Cu were produced by casting. Their dimensional stability and microstructures were investigated in the as-cast and heat-treated conditions.In a lubricated sliding wear test, a comparison was made of the wear behaviour of these alloys with that of SAE 660 phosphor bronze. It was shown that the Zn-Al-Si alloys were the best materials of those tested in terms of dimensional stability and higher wear resistance under intermediate speed and high load conditions.     

Sliding wear of cast zinc-based alloy bearings under static and dynamic loading conditions

The lubricated wear behaviour of cast journal bearings, produced from a series of zinc-based alloys and SAE 660 bronze as a reference material, was investigated under both static and dynamic loading conditions using a bearing test rig. All of the zinc-based alloys had higher wear resistance than the SAE 660 bronze. Among the zinc-based alloys, the wear resistance of the monotectoid-based alloys was superior to those based on near-eutectoid composition, and the best wear performance under both static and dynamic loading conditions was obtained with ZnAl40Cu2Si1 alloy. Copper content affected the wear resistance of monotectoid zinc-based alloys. Under dynamic loading conditions, it increased with increasing copper content up to 2%, but declined thereafter. Tensile properties and hardness of the monotectoid alloys were also affected by their copper content. Loading conditions had a strong influence on the wear rate. Under static loading conditions, as-cast zinc-based alloys showed higher wear resistance than the equivalent heat-treated alloys, but this behaviour was reversed for dynamic loading. Possible reasons for this are briefly discussed.     

Mechanical and tribological properties of Al-40Zn-Cu alloys

One binary Al-40Zn and five ternary Al-40Zn-Cu alloys with different copper contents were prepared by permanent mould casting. Their microstructure and mechanical properties were investigated in as-cast state. Friction and wear properties of the ternary alloys were studied using a conforming block-on-disc type tester. The results obtained were compared with those of SAE 65 bearing bronze.The microstructure of Al-40Zn-Cu alloys consisted of aluminium-rich α dendrites surrounded by eutectoid α+η phases and θ (CuAl₂) particles. Hardness of the ternary alloys increased continuously with increasing copper content, but their tensile strength decreased above 3% Cu. Friction coefficient and temperature of the Al-40Zn-Cu alloys and bronze increased in the initial period of run. This was followed by a reduction in the properties and attainment of constant levels afterwards. However, volume loss of the alloys increased rapidly at the beginning of the test run and reached almost constant levels after a sliding distance of approximately 400 km. The Al-40Zn-Cu alloys were found to be much superior to the SAE 65 bronze, as far as their wear resistance is concerned. Among the alloys tested, highest strength and wear resistance were obtained with the Al-40Zn-3Cu alloy.     

Dry Sliding Friction and Wear Properties of Al–25Zn–3Cu–(0–5)Si Alloys in the As-Cast and Heat-Treated Conditions

Dry sliding friction and wear properties of ternary Al–25Zn–3Cu and quaternary Al–25Zn–3Cu–(1–5)Si alloys were investigated using a pin-on-disc test machine after examining their microstructures and mechanical properties. An alloy (Al–25Zn–3Cu–3Si), which exhibited the highest tensile and compressive strengths, was subjected to T7 heat treatment. Surface and subsurface of the wear samples were investigated using scanning electron microscopy (SEM). The hardness and both tensile and compressive strengths of the alloys increased with increasing silicon content, but the trend reversed for the latter ones above 3% Si. It was observed that T7 heat treatment reduced the hardness and both tensile and compressive strengths of the Al–25Zn–3Cu–3Si alloy, but increased its elongation to fracture greatly. Three distinct regions were observed underneath the surface of the wear samples of the Al–25Zn–3Cu–3Si alloy. The formation of these regions was related to the heavy deformation of surface material and mixing, oxidation and smearing of wear material. Al–25Zn-based ternary and quaternary alloys in both as-cast and heat-treated conditions were found to be superior to SAE 660 bronze as far as their mechanical and dry sliding wear properties are concerned.     

Mechanical wear behaviour of copper-base alloys

In an endeavour towards better understanding of the mechanical wear behaviour of copper and of the influence of the main contributing variables on it, wear test were carried out on some copper alloys with different percentages of alloying elements. The investigation concludes and confirms that mechanical wear increases with load and sliding speed both with and without lubricant. Results reveal that the resistance to wear of alloys may be improved by increasing their strength, toughness and hardness and by decreasing the Young's modulus of elasticity, which can be obtained by controlling the type and amount of alloying elements.     

The unlubricated adhesive wear resistance of metastable austenitic stainless steels containing silicon

The unlubricated adhesive wear resistance of metastable austenitic stainless steels can be improved by silicon additions. At low surface temperatures (under the M_d temperature) metastability appears helpful in maintaining the alloy in a state of mild wear. Silicon was not found to promote alloy metastability but did tend to strengthen the alloy by solid solution hardening. At lower temperatures the silicon had little effect on the mild wear rates of metastable alloys but did act to lower the severe wear rates of stable alloys. At high surface temperatures (above the M_d temperature) the silicon additions (2–4%) were found very beneficial in promoting mild wear rates while metastability had little or no effect. Silicon additions were also found to be beneficial to the oxidation resistance and did not increase the running-in period for the alloys. Improving the oxidation resistance of these alloys is more effective in promoting mild wear than is increasing the hardness through metastability.     

采煤机滑靴等离子熔覆高铬铁基合金的摩擦学性能

采煤机导向滑靴工作环境恶劣,受力复杂,导致其经常因为磨损和开裂而失效。为提高采煤机导向滑靴耐磨性,采用等离子熔覆技术在调质45#钢基材表面熔覆一层高铬铁基合金,在保持基体良好的综合机械性能的情况下,得到具有高强度、高硬度、高耐磨、耐腐蚀的高铬铁基合金熔覆层,既节省了合金材料的使用,又满足了煤矿复杂条件下对采煤机滑靴材料性能的要求。高铬铁基合金熔覆层在高载下具有较低的摩擦因数,可降低设备运转时的能量耗损;抗黏着磨损和磨粒磨损能力较强,可提高滑靴的使用寿命。     

Effect of microstructure and mechanical properties on the seizure resistance of cast aluminium alloys

Seizure resistance of several cast aluminium base alloys has been examined using a standard Hohman Wear Tester. Disks of aluminium base alloys were run against a standard aluminium 12% silicon base alloy. The seizure resistance of the alloys (as measured by the lowest bearing parameter reached before seizure) increased with hardness, yield and tensile strength. In Al-Si-Ni alloys where silicon and nickel have little solid solubility in α-aluminium and Si and Ni Al₃ hard phases are formed, the minimum bearing parameter decreased with the parameter V (The product of vol. % of hard phases in the disk and the shoe). Apparently the silicon and NiAl₃ particles provided discontinuities in the matrix and reduced the probability (1 ? V) of the α-aluminium phase in the disk coming into contact with the α-aluminium phase in the shoe. The copper and magnesium containing Al-Si-Ni alloys with lesser volumes of hard phases exhibit considerably better seizure resistance indicating that a slight increase in the solute content or the hardness of the primary α-phase leads to a considerable increase in seizure resistance. Deformation during wear and seizure leads to fragmentation of the original hard particles into considerably smaller particles uniformly dispersed in the deformed α-aluminium matrix.     

Effects of Silicon Content on the Mechanical Properties and Lubricated Wear Behaviour of Al–40Zn–3Cu–(0–5)Si Alloys

In this work, one ternary Al–40Zn–3Cu and seven quaternary Al–40Zn–3Cu–(0.25–5)Si alloys were synthesized by permanent mould casting. Their microstructure, mechanical and lubricated wear properties were investigated using appropriate test apparatus and techniques. As the silicon content increased the hardness of the alloys increased, but their elongation to fracture decreased. Tensile strength of the alloys decreased with increasing silicon content following a sharp decrease and a slight increase. Among the silicon-containing quaternary alloys the highest and the lowest tensile strength values (348 and 305 MPa) were obtained with the Al–40Zn–3Cu–2Si and Al–40Zn–3Cu–5Si alloys, respectively, while the base alloy (Al–40Zn–3Cu) exhibited a tensile strength of 390 MPa. However, the volume loss due to wear of the alloys increased with increasing silicon content after showing an initial increase and a sharp decrease. The lowest wear loss was obtained with the alloy containing approximately 2% Si which has the highest tensile strength among the quaternary alloys containing more than 0.25% Si. Wear surfaces of the alloys were characterized mainly by smearing indicating that adhesion is the dominant wear mechanism for the experimental alloys.     

Influence of Test Conditions on the Lubricated Friction and Wear Behaviour of Al–25Zn–3Cu Alloy

The friction and wear properties of Al–25Zn–3Cu alloy were investigated over a range of oil flow rate, pressure and sliding speed using a pin-on-disc machine, after examining its microstructure and mechanical properties. The results obtained were compared with those of a conventional-bearing material (SAE 65 bronze). It was observed that the microstructure of the Al–25Zn–3Cu alloy consisted of aluminium-rich α, eutectoid α + η and θ phases, while the microstructure of the SAE 65 bronze revealed copper-rich α, and eutectoid α + δ phases. It was found that the friction coefficient, temperature and wear volume of both the alloys decreased sharply with increasing oil flow rate and attained almost constant levels beyond a certain range of oil flow rate. It was also found that the friction coefficient and the wear volume of the alloys decreased with increasing pressure, but was observed to be almost independent of the sliding speed. The Al–25Zn–3Cu alloy exhibited higher wear resistance as compared to that of the bronze under all the test conditions. Smearing type of adhesion appeared to be the most effective wear mechanism for the Al–25Zn–3Cu alloy, while abrasion dominated one for the SAE 65 bronze.     

Effects of cold working and heat treatment on microstructure and wear behaviour of Cu–Be alloy C17200

The effects of cold work process between aging and solution heat treatment on the microstructure, hardness and the tribologic behaviour of a copper–beryllium (Cu–Be) alloy C17200 were investigated. The wear behaviour of the alloys was studied using ‘pin on disc’ method under dry conditions. The results show that the formation of fine grained structure and γ phase particles enhances the mechanical properties of the alloy; nonetheless, they do not reduce the wear rate. This is attributed to the capability of the softer specimens to maintain oxygen rich compounds during the dry sliding test.     

Effect of copper content on the mechanical and sliding wear properties of monotectoid-based zinc-aluminium-copper alloys

One binary zinc-aluminium monotectoid and five ternary zinc-aluminium-copper alloys were produced by permanent mould casting. Their wear properties were examined using a block-on-ring test machine. Hardness, tensile strength and percentage elongation of the alloys were also determined and microhardness of aluminium-rich α phase was measured.It was observed that the hardness of the alloys increased continuously with increasing copper content up to 5%. Their tensile strength also increased with increasing copper content up to 2%, but above this level the strength decreased as the copper content increased further. Microhardness of the aluminium-rich α phase was also affected by the copper content in a manner similar to that of the tensile strength. It was found that the wear loss of the alloys decreased with increasing copper content and reached a minimum at 2% Cu for a sliding distance of 700 km. However, the coefficient of friction and temperature due to frictional heating were found to be generally less for the copper containing alloys than the one without the element. The effect of copper on the wear behaviour of the alloys was explained in terms of their microstructure, hardness, tensile strength, percentage elongation and microhardness of the α phase.     

钛硼合金元素对特殊铜合金性能的影响

研究了加硼钛后铜合金的组织变化及力学和耐磨性能。结果表明 ,硼钛能明显细化铜合金的组织 ,提高其强度、硬度 ,改善其耐磨性 ,塑性虽有所降低 ,但不影响其综合性能。     

Dry Sliding Wear Behavior of Palmyra Shell Ash–Reinforced Aluminum Matrix (AlSi10Mg) Composites

High strength, light weight, ease of fabrication, excellent castability, and good wear resistance make aluminum alloy composites suitable for commercial applications. In this work, a silica-rich ash particle (palmyra shell ash) was reinforced with aluminum alloy (AlSi10Mg) composites and its mechanical and tribological properties were studied. The aluminum alloy was reinforced with 3, 6, and 9 wt% of palmyra shell ash particles, and its dry sliding wear behavior was studied using a pin-on-disc machine under different loading conditions. The result shows that the dry sliding wear resistance of Al–palmyra shell ash composites was almost similar to that of fly ash– and rice husk ash–reinforced Al-alloy composites and these composites exhibit better wear resistance compared to unreinforced alloy. The palmyra shell ash particle weight fraction significantly affects the wear and friction properties of the composites. Scanning electron microscopic examination of the worn surface reveals that at various loads palmyra shell ash particles act as load-bearing constituents and the wear resistance of the reinforced palmyra shell ash with a size range of 1–50 µm was superior to that of unreinforced alloy. Mechanical properties (hardness and tensile strength) were also studied and it was observed that the reinforced Al-alloy showed a significant increase in mechanical properties.     

Effect of reinforcement on wear behaviour of aluminium hybrid composites

Abstract

Aluminium metal matrix composites are among the recent developments in engineering applications to meet the present day need of light weight, high strength/weight ratio and good wear properties. In the present study, AlSi10Mg alloy reinforced with 3, 6 and 9 wt-% alumina with constant 3 wt-% graphite particles was produced by stir casting technique. Microstructural investigations as well as evaluation of mechanical properties such as hardness, tensile strength and double shear strength were conducted on composites and unreinforced alloy specimens. Tribological behaviour of hybrid composites was studied using pin on disc test machine. Wornout surfaces were analysed using scanning electron microscopy, and wear debris were analysed using X-ray diffraction. Results revealed that the mechanical properties of hybrid composites were higher than unreinforced alloy. Dry sliding wear test results indicated that the aluminium alloy reinforced with 9 wt-% alumina and 3 wt-% graphite has highest wear resistance compared to unreinforced alloy.     

Wear behavior of Al-Mg-Cu-based composites containing SiC particles

The friction and wear behavior of Al-Mg-Cu alloys and Al-Mg-Cu-based composites containing SiC particles were investigated at room conditions at a pressure of 3.18 MPa and a sliding speed of 0.393 m/s using a pin-on-disk wear testing machine. This study is an attempt to investigate the effects of adding copper as alloying element and silicon carbide as reinforcement particles to Al-4 wt% Mg metal matrix. The wear loss of the copper containing alloys was less than that for the copper free alloys. It was observed that the volume losses in wear test of Al-Mg-Cu alloy decrease continuously up to 5%. Also it was found that the silicon carbide particles play a significant role in improving wear resistance of the Al-Mg-Cu alloying system. The formation of mechanically mixed layer (MML) due to the transfer of Fe from counterface disk to the pin was observed in both Al-Mg-Cu alloys and Al-Mg-Cu/SiC composites.     

铜包石墨含量对铜锰铝复合材料摩擦磨损性能的影响

为改善铜锰铝合金的烧结性能,并提高其在干摩擦下的摩擦磨损性能,以铜包石墨作为自润滑相加入到铜锰铝合金中,采用等离子真空压力烧结方法制备铜锰铝/石墨复合材料,分析铜包石墨含量对复合材料的密度、硬度的影响,探讨不同复合材料在干摩擦和油润滑条件下的摩擦磨损性能.结果表明:相比真空和氢气还原气氛下的烧结方式,等离子体烧结铜锰铝...     

Cr5系堆焊合金碳、铬过渡形式对高温磨损性能影响的研究

在轧辊堆焊复合制造中,为节约贵重碳化物及提高堆焊材料的性价比,在堆焊熔敷金属成分基本保持不变的条件下,利用埋弧堆焊研究药芯焊丝碳、铬不同加入方式对堆焊合金微观组织与性能的影响。通过磨损试样前后硬度、高温拉伸、常温韧性与高温磨损量的量化,结合磨损前后金相组织、扫描电镜等辅助手段分析微观组织、加入方式与耐磨性之间的关系;结果表明:堆焊金属600℃的高温耐磨性能与合金高温强度及硬度呈正比,并随合金韧性的增加耐磨性能提高;直接加石墨和铬粉的药芯焊丝堆焊熔敷金属的耐磨性能优于在焊丝中直接加碳化铬的堆焊熔敷金属。高温磨损是合金氧化、切削、疲劳开裂与剥离等多种因素作用的结果,理想的高温耐磨堆焊材料不仅与采用的堆焊合金系有关,还与堆焊金属的显微组织、抗氧化性能及高温强韧性等因素有关。同时得出改变合金的加入方式是不添加变质剂及外加激振法外,能够促使组织均匀及强化熔敷金属的另一种方式。     

Effect of Copper Content on the Mechanical and Tribological Properties of ZnAl27-Based Alloys

One binary ZnAl27- and five ZnAl27-based ternary alloys containing 1–5% Cu were produced by permanent mould casting. Their friction and wear properties were examined using a block-on-ring test machine after determining their hardness and tensile strength. It was observed that the hardness and tensile strength of the ZnAl27-based ternary alloys increased with increasing copper content up to 2% due to solid-solution hardening, above which their tensile strength decreased, while hardness continued to increase. This is attributed to the formation of copper-rich and T phases, which reduce the solid-solution hardening of the alloys. It was found that the wear volume loss of the ZnAl27-based alloys decreased with increasing copper content up to 2% but showed a small increase above this level. Therefore, it was concluded that the wear resistance of ZnAl27-based alloys containing 1 to 5% Cu correlates well with their tensile strength. In addition, smearing and scratches were found to be the main features of the wear surfaces of the ZnAl27-based alloys under static loading and lubricated sliding conditions.     

7003合金双峰时效工艺研究

采用洛氏硬度计、显微硬度计、光学显微镜（OM）、拉伸试验机等技术对7003铝合金时效行为、力学性能及组织进行了研究。结果表明,7003合金的硬度及强度都具有时效双峰特征。两个时效峰的硬度和强度相差不多,在较低温度下,时效第二峰的强度、硬度、塑性、韧性较高。