摘要:

AbstractThe laser surface cladding technique was used to form in situ Fe–Cr–Mn–C alloys on AISI 1016 steel substrate. In this process, mixed powders containing Cr, Mn, and C in the weight ratio 10: 1 : 1 were delivered using a screw feed, gravity flow, carrier gas aided system into the melt pool generated by a 10 kW CO2laser. This technique produced an ultrafine microstructure in the clad alloy layer. The microstructure of the laser surface clad region was investigated by optical, scanning and transmission electron microscopy, and X-ray microanalysis techniques. Microstructural study showed a high degree of grain refinement and an increase in solid solubility of alloying elements which, in turn, produced a fine distribution of complex types of carbide precipitates in the ferrite matrix because of the high cooling rate. An alloy of this composition does not show any martensitic transformation or retained austenite phase.MST/356

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.7.709

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractComposition varies sufficiently widely within an alloy specification to allow significant variations in the temperature ranges within which the austenite phase transforms to martensite. It has been suggested that such variations in composition are associated with anomolous fluctuations in the distortions produced in quenched components of a particular alloy. In the present work, a plane stress infinite plate mathematical model was used to conduct a quantitative examination of the connection between these compositional variations, the associated changes in the Msand Mftemperatures, and the amount of residual stress and strain after quenching. The residual strains at the end of a water quench increased substantially as the Mstemperature increased. However, the corresponding stresses after the same water quench and both the residual stresses and strains at the end of an oil quench were only slightly affected by such changes in the Mstemperature. This displacement in the temperature range within which transformation occurred reduced the absolute value of the transformation strain, one of the components contributing to total strain. At the end of the quench the sum of the other strain components was positive and larger than the negative transformation strain, so the reduction in the absolute value of the latter, associated with the increase in the Mstemperature, led to the increase in the residual strain at the end of the quench. The results obtained support the suggestion that the limitations of fluctuations in composition within the alloy specification are beneficial to the control of distortion in quenched components, although the most desirable compositions are those that produce a lower rather than a higher Mstemperature.MST/367

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.7.714

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe cost of failures in gas turbine discs, both in human life and financial terms, is particularly high, and it has always been recognized that the component must be fully specified against the design requirement, and totally predictable in operation. This was originally achieved by making a reproducible forging consistent with the design strength assumptions and which approached the engineer's model of the material as‘elastic, isotropic, and free from defects’. Today's improved understanding of materials behaviour in terms of the relationship between material property and microstructure, together with the designer's need for higher–strength materials, has led to an approach which now recognizes the role of both structure and‘defects’within the forging. This, and the need to improve the cyclic properties of components, is now imposing on the forger complex microstructural and quality requirements that can be met only by process control and by a move towards closer-to-size and more complex shape requirements. Future material needs are discussed in relation to controlling the discontinuity behaviour, together with the change in philosophy that this is bringing to the control of the manufacturing process.MST/255

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.7.721

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractDuring the past forty years, a range of forged nickel–base alloys with progressively increasing strength and alloying complexity has been developed. They are used in a variety of arduous applications which demand the highest standards of billet integrity. Some of the possible manufacturing techniques are reviewed in this paper, along with the control of various defect types. To ensure quality and consistency of product integrity, a system of review and verification of process control data is outlined, along with the usual inspection and product testing techniques.MST/256

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.7.728

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe characteristics of press forging techniques for superalloys are reviewed in the context of the available equipment. The use of thermomechanical processing to meet specific microstructural and ultrasonic requirements is discussed in some detail, and examples are given which cover a wide range of superalloy compositions and structural requirements. Data are presented which demonstrate the all-important factors of repeatability and consistency in manufacture which can be obtained by press forging. The influence of die temperature on forging surface characteristics is outlined.MST/257

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.7.733

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.7.741

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractForging technology has been developed to the point where wrought nickel alloy turbine blades can be manufactured to accurate dimensional tolerances and consistent metallurgical characteristics. Metallurgists and engineers have utilized theoretical knowledge and practical understanding of nickel superalloys and the forging process to meet the ever-increasing temperature and stress demands of turbine engines. New materials, forging techniques, and the use of computer-aided design and manufacturing systems are being developed to compete with advanced casting technology.MST/259

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.7.742

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.7.748

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

摘要:

AbstractThe main superalloy forgings required for gas turbine engines (engine discs and blades) are currently made by well established processes. These‘conventional’techniques have been developed to a high degree of effectiveness, but further advances are still required. The achievement of controlled microstructures and the avoidance of defects necessitates strict control of the forging process. Some ways of improving control beyond the present capability are indicated; these will be largely through increased automation and improved computer modelling. If achievable, such improvements could lead to great changes in non–destructive test procedures. Various less conventional forging processes are considered, and are grouped according to their main characteristics: size, speed, temperature, and environment. Some specialized techniques are likely to be required for the production of newer materials, whether superalloys or alternative materials. It is probable, however, that the widely used forging processes of the future will be recognizably derived from those of the present.MST/261

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.7.749

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor

ISSN:0267-0836    

DOI:10.1179/mst.1986.2.7.755

出版商:Taylor&Francis    

年代:1986

数据来源: Taylor