Thermal spray applications in powertrain contribute to the saving of energy and material resources

Thermal spray technology has found its way into the automotive industry and is widely used for an expanding range of applications. A variety of thermal spray processes are available for coating applications on parts of the piston group, the clutch, the gearbox and the valve train.More than six years ago a leading European manufacturer of passenger cars has put a thermal spray process into series production, to coat cylinder bore surfaces of aluminium engine blocks from high power diesel engines. The coating, with its particular surface topography, decreases the friction of the piston group significantly, leading to a reduction of fuel consumption of 2-4%. In addition to fuel savings the oil consumption can be reduced by a factor of 2-3 and therefore help to achieve lower emission values. Based on this cylinder bore coating technology Sulzer Metco has developed a range of materials to provide optimum solutions for the different types of engines with their specific requirements. These materials cover the needs for high corrosion resistance in marine engines or engines run on biofuels, abrasion resistance in heavy duty truck engines or very low friction in racing engines. This paper will focus on plasma spray coating of cylinder liners for heavy duty diesel (HDD) truck engines and highlight the technical feasibility for the measure of cost reduction in series production.     

Reviewing sulfidation corrosion—Yesterday and today

At one time, sulfidation corrosion threatened to severely limit the use of gas turbines in marine applications, markedly reduce the life of industrial gas turbines, and affect the performance of aircraft engines. Today, gas turbine engines drive U.S. naval ships, produce electricity, and power aircraft. However, the problem of sulfidation corrosion has not disappeared. The rapid rate of degradation of airfoil materials in the presence of condensed sulfates is still a concern for gas turbine engines that operate in industrial and marine environments.     

Thermal barrier coatings for industrial gas turbine applications: An industrial note

Thermal barrier coatings (TBCs) have been used in high-thrust aircraft engines for many years to pro-vide thermal protection and increase engine efficiencies. TBC life requirements for aircraft engines are typically less than those required for industrial gas turbines. This paper describes current and future ap-plications of TBCs in industrial gas turbine engines. Early testing and applications of TBCs are reviewed. Areas of concern from the engine designer’s and materials engineer’s perspective are identified and evaluated. This paper focuses on the key factors that are expected to influence utilization of TBCs in ad-vanced industrial gas turbine engines. It is anticipated that reliable, durable, and highly effective coating systems will be produced that will ultimately improve engine efficiency and performance.     

汽车发动机再制造效益分析及表面工程技术的应用

对3000台斯太尔发动机的统计分析表明，可直接利用的零件数量占23．7％，重量占14．4％，价值占12．3％；经再制造加工可以使用的零件数量占62％，重量占80．1％，价值占77．8％，说明对旧发动机进行再制造有良好的基础。按年产l万台再制造发动机统计，可回收附加值3．59亿元，节省金属8．5kt，创造税金0．36亿元，节电1600万度，减少CO2排放13～17kt，并可提供330人的就业机会；旧发动机中62％的失效零件可以运用表面工程技术进行修复，修复后的表面性能优于新品。先进表面工程技术在发动机再制造中的应用，提高了旧品利用率，降低了再制造成本，不仅使企业获得了经济效益，还为国家节能、节材、保护环境作出了贡献。     

The potential for CMCs to replace superalloys in engine exhaust ducts

The Materials Systems Laboratory at the Massachusetts Institute of Technology has conducted research to develop decision tools that can facilitate materials selection and provide a deeper understanding of the design tradeoffs that occur when choosing among advanced aerospace materials for high-temperature applications. As an illustration of the use of these tools, this paper describes research done to evaluate the material alternatives currently under consideration for exhaust ducts in aircraft gas turbine engines. Although nickel-based superalloys currently prevail for this application, the increasing temperatures of modern engines are necessitating the usage of higher temperature materials.     

Application of thermal spraying in the automobile industry

New advanced thermal spray technology, provides wear resistant coatings on the cylinder surface of aluminum or magnesium engines. The special surface topography obtained after the finishing allows us to decrease significantly the coefficient of friction and to decrease the fuel consumption by an amount of 2 to 4%.Engine tests on diesel and gasoline engines have confirmed the value of this technology for energy saving.This coating technology was introduced 4 years ago in Europe by the manufacturers of high power diesel and gasoline engines. The combination of different MMC coating materials allows the development of new specific solutions for each type of engine. Coatings with improved corrosion resistance and abrasion resistance were also developed and are available now. A brief overview of other applications of thermal spraying in the automotive industry will also be given.     

Selecting high-temperature structural intermetallic compounds: The materials science approach

Some 300 intermetallic compounds with high melting temperatures are candidate materials for the high-temperature turbines and engines of the future. Before these applications can be realized, however, the limited ductility of intermetallic materials must be overcome. Using melting temperature and density as figures of merit, and considering the effects of composition and crystal structure, the most likely candidates for these high-performance applications may be identified.     

涡轮叶片专用探头研制与应用

介绍叶片专用探头设计原理，及其与SMART97型智能双频涡流探伤仪配套使用的情况，专专用探头在飞机发动机二级涡轮叶片探伤中具有良好应用前景。     

Intermetallics: Why is it so difficult to introduce them in gas turbine engines?

The intermetallic systems are considered as potential substitutes to metallic alloys for aerospace applications. An enormous research activity was spend during the last 30 years to develop applications of NiAl and TiAl. Although successful technical results were obtained, no applications are yet visible in aero engines. This paper explains the main reasons of this situation. The first reasons are due to the materials’ intrinsic properties (brittleness, small range of operating temperature, unfavourable property balance, scattered properties). The other reasons are manufacturing related (difficult processing, high cost). This is illustrated by NiAl and TiAl applications; some criteria for successful applications are given.     

Overview of thermal barrier coatings in diesel engines

An understanding of delamination mechanisms in thermal barrier coatings (TBCs) has been developed for diesel engine applications through rig tests, structural analysis modeling, nondestructive evaluation, and engine evaluation of various TBCs. This knowledge has resulted in improved TBCs that survive se-vere cyclic fatigue tests in high-output diesel engines. Although much conflicting literature now exists regarding the impact of TBCs on engine performance and fuel consumption, changes in fuel consumption appear to be less than a few percent and can be nega-tive for state-of-the-art diesel engines. The ability of the TBC to improve fuel economy depends on a num-ber of factors, including the fuel injection system, combustion chamber design, and initial engine fuel economy. Limited investigations on state-of-the-art diesel engines have indicated that surface- connected porosity and coating surface roughness may influence engine fuel economy. Current research efforts on TBCs are primarily directed at reduction of in-cylinder heat rejection, ther-mal fatigue protection of underlying metal surfaces, and possible reduction of diesel engine emissions. Significant efforts are still required to improve the plasma spray processing capability and the economics for complex-geometry diesel engine components.     

热障涂层的研究动态及应用

对有关热障涂层系统的组成及材料性能进行了综述,讨论了陶瓷层和结合底层目前的不同制造方式,以及热障涂层的失效机理,介绍了热障涂层系统在燃气轮机和柴油机中的改进设计及其应用。     

Tribological Properties of Al Alloy Particle Composites

In recent years, a variety of particle dispersed aluminum alloy composites have been synthesized. The tribological properties of these materials include sliding wear, friction, seizure resistance and abrasive wear (of composites containing solid lubricant as well as hard ceramic particles). The potential high-performance applications of Al-alloy-graphite composites include pistons for internal combustion engines and bearings. For such applications, the low stress abrasive wear rates of composites, containing high volume fractions (0.20–0.35), are comparable to that of heat treated 1045 steel.     

Metal- and intermetallic-matrix composites for aerospace propulsion and power systems

Successful development and deployment of metal-matrix composites and intermetallic- matrix composites are critical to reaching the goals of many advanced aerospace propulsion and power development programs. The material requirements are based on the aerospace propulsion and power system requirements, economics, and other factors. Advanced military and civilian aircraft engines will require higher specific strength materials that operate at higher temperatures, and the civilian engines will also require long lifetimes. The specific space propulsion and power applications require hightemperature, high-thermal-conductivity, and high-strength materials. Metal-matrix composites and intermetallic-matrix composites either fulfill or have the potential of fulfilling these requirements.     

WROUGHT TiAl ALLOY DESIGN

１　ＩＮＴＲＯＤＵＣＴＩＯＮＳｉｎｃｅｔｈｅｆｉｒｓｔｍｅａｓｕｒｅｍｅｎｔｓｏｆｍｅｃｈａｎｉｃａｌｐｒｏｐｅｒｔｉｅｓａｎｄｏｘｉｄａｔｉｏｎｒｅｓｉｓｔａｎｃｅｉｎａｂｉｎａｒｙＴｉＡｌｃａｓｔａｌｌｏｙｉｎｔｈｅｅａｒｌｙ１９５０’ｓ，ｅｎｓｕｉｎｇｒｅｐｏｒｔｓ［１－４］ｈａｖｅｃｏｎｆｉｒｍｅｄｖａｒｉｏｕｓｐｒｏｐｅｒｔｉｅｓｂｅｎｅｆｉｃｉａｌｔｏｈｉｇｈｔｅｍｐｅｒａｔｕｒｅｓｔｒｕｃｔｕｒａｌａｐｐｌｉｃａｔｉｏｎｓｉｎｃｌｕｄｉｎｇｌｏｗｄｅｎｓｉｔｙ，ｅｘｃｅｌｌｅｎ…     

Development of coatings for protection in specific high temperature environments

Metallic and intermetallic coatings are widely used in jet engines and land-based gas turbines for oxidation and corrosion protection in the hotter parts of the engines. However there is a significant number of industrial processes where the use of protective coatings at high temperatures could contribute to a significant extension of life-time or an increase in operation temperature and thus efficiency. Examples of such industries are incineration and gasification of waste, biomass and coal, chemical process industries and petrochemical plants where highly aggressive environments are encountered containing species of e.g. carbon, chlorine, sulphur, vanadium or alcalines. Since most of these process environments contain only very low oxygen partial pressures or exhibit high concentrations of extremely aggressive compounds, the conventional, uncoated materials come to their limits. In recent years in laboratory work a number of new types of coatings have been developed for high-temperature applications which include diffusion coatings, overlay coatings and nanotechnological approaches for sealing porosity. In the paper the background of this development and the thermodynamic fundamentals are discussed together with some more recent solutions based on synergistic effects of multi-element coatings. Some results of performance tests of these coatings in sulfidizing, carburizing, chloridizing and vanadate environments will be presented. At the end conclusions can be drawn on the suitability of the different types of coatings for their specific applications.     

Structural honeycomb materials for advanced aerospace designs

With their high stiffness and low weight, honeycomb materials are becoming an increasingly important element of advanced aerospace design concepts. For example, honeycomb materials have found usage for noise damping and abradable seal applications in modern jet engines, and actively cooled honeycomb structures may be the basis of wing and fuselage design for the proposed national aerospace plane. Numerous factors influence the applicability of metallic-based honeycomb structural materials for different applications, including availability, manufacture and cost.     

Progress in structural materials for aerospace systems

This paper examines the progress in aircraft and aircraft engines from the standpoint of the role that better materials and processing has played. Such progress includes the relatively recent transformation of the aircraft industry from purely performance driven products to products that are driven by customer value. It is demonstrated that advances in materials and processing technology and understanding has enabled much of the progress that has been made since the inception of manned, heavier than air flight. The recent constraints of cost, as determined by customer value, have changed the way new materials are introduced and these trends appear to be the new paradigm for the aircraft and aircraft engine industry.While the focus of this paper is aircraft and aircraft engines, the broader focus is on the role of materials in creating lightweight structures. There are examples used in this paper that are relevant to automotive applications once they are adjusted for cost. This matter is briefly discussed at the end of the paper.     

Assessment of the Oxidation Behavior of a Pt-Based Alloy for High Temperature Applications

Pt-based alloys are being developed as a possible future replacement for Ni-based superalloy components in the hottest section of turbine engines. The critical properties of these alloys are their ability to withstand higher thermal and mechanical stresses as well as to resist aggressive corrosive and oxidizing environments in applications. Oxidation properties of these alloys were investigated between 1150 and 1350 °C. The surface roughness of the as-polished samples was determined using atomic force microscopy, while the microstructures of both the as-polished and oxidized samples were examined using scanning electron microscopy. The alloy was found to be composed of a two-phase gamma/gamma prime microstructure, while the average surface roughness decreased from 5.78 nm after 1 μm diamond paste polishing to 4.13 nm with 0.25 μm diamond paste polishing. Microstructure examination of the oxidized alloy samples revealed the formation of compact and protective external oxide scale composed of α-alumina, as confirmed by the XRD and Raman spectroscopy. The results also showed that the oxide scale thickens with increased exposure time and temperatures according to parabolic kinetics. It was concluded from the results that the Pt-based alloys possess good oxidation resistance and thus will be suitable for high temperature applications, such as turbine engines.     

CermeTi® discontinuously reinforced Ti-matrix composites: Manufacturing,properties, and applications

Advanced powder-metallurgy technology has led to the development of the CermeTi® family of titanium metalmatrix composites. Reinforcing the titanium alloy matrix with titanium carbide or titanium boride particles results in superior properties. These discontinuously reinforced titanium composites have excellent room- and elevated-temperature properties and are exceptionally wear resistant. High quality, near-net shape CermeTi composite components are being produced commercially and are being evaluated for potential applications in military vehicles, commercial automotive engines, sporting goods, industrial tooling, and biomedical devices.     

Mo—Si—B合金的制备及性能研究现状

综述了Mo—Si—B合金的研究现状,分别从制备工艺、抗氧化性、断裂韧性、微观结构等方面进行了综述。Mo—Si—B合金可以作为新一代的航空发动机用结构材料和高温抗氧化涂层材料。研究表明,Mo—Si—B合金具有更加优异的高温力学性能和高温抗氧化性能。最后讨论了Mo—Si—B合金未来的发展方向。