ISSN:0267-0844    

DOI:10.1179/sur.1991.7.3.171

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

ISSN:0267-0844    

DOI:10.1179/sur.1991.7.3.172

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

ISSN:0267-0844    

DOI:10.1179/sur.1991.7.3.175

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

ISSN:0267-0844    

DOI:10.1179/sur.1991.7.3.192

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

ISSN:0267-0844    

DOI:10.1179/sur.1991.7.3.197

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractAn investigation has been carried out on a series of 22 grey cast irons to determine the influence of carbon equivalent and sulphur content on tensile strength, and on the ability of cast iron to develop a roughened surface under the action of a high speed open arc weld deposition process. The tensile strength decreased linearly with increasing carbon equivalent, in the expected manner, but showed no significant dependence on sulphur content. The surface roughness, quantified as the mean aspect ratio of the deposited weld metal droplets, showed a significant dependence on carbon equivalent and a very strong dependence on sulphur content. The effect exerted by sulphur on the roughening phenomenon was shown to be consistent with a model developed earlier to account for the surface perturbations formed under the action of a gas tungsten arc. In the model, sulphur exerts a strong depressive influence on the surface tensions which exist in the system, but since its effect on the solid-vapour surface tension is greater than on the liquid-vapour surface tension, non-wetting tends to develop as the sulphur content increases. The results have been used to formulate a modified grey cast composition for the manufacture of sugar cane crushing roll shells, which possesses both adequate strength, by virtue of its lowered carbon equivalent, and an adequate roughening ability, by virtue of its enhanced sulphur content.

ISSN:0267-0844    

DOI:10.1179/sur.1991.7.3.201

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractWear resistant coatings produced by physical vapour deposition (PVD) techniques are gaining increasingly widespread industrial acceptance, particularly as a means of providing improvements in service life and product quality when used on cutting tools, on casting, moulding, and extrusion dies, and in a variety of other materials processing applications. Titanium nitride coatings are now widely used and second generation alloy coatings such as, for example, Ti(C,N), Ti(B,N), (Ti,Al)N, and (Ti,W)C are being considered for specific wear situations. The next stage in extending the applicability of plasma assisted P VD processing is likely to be in the area of third generation multicomponent coatings, which may incorporate multilayers and/or duplex diffusion/coating plasma treatments. These new combined treatments will primarily be designed to improve coating durability (particularly with regard to toughness and corrosion resistance). The use of alternative substrate materials which are cheaper, lighter, and/or more corrosion resistant than traditional tool steels will therefore also become increasingly important. In order to achieve good coating support with these 'new' materials, plasma diffusion or implantation treatments are likely to play a major role, especially if adequate coating-substrate adhesion is to be maintained. This paper investigates the duplex low pressure triode plasma diffusion/coating treatment of ASP 23 tool steel and demonstrates that plasma nitriding has the potential to provide substantial improvements in PVD coating support, if appropriate treatment conditions are employed. The plasma theory behind the suitability of low pressure triode plasmas for precoating diffusion treatments is examined, with particular regard to surface oxide removal by argon-hydrogen plasma precleaning and white layer control by adjustment of the nitriding discharge parameters. The performance of the nitrided/coated (TiN) system under scratch adhesion testing is also discussed.

ISSN:0267-0844    

DOI:10.1179/sur.1991.7.3.207

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractThe electrochemical behaviour of sediment electrodeposited nickel-silicon nitride composite coatings on mild steel has been studied. These composite coatings provide better corrosion resistance in both 3.5% NaCl and 0.5M H2SO4solution than nickel coatings. The higher the percentage of silicon nitride in the composite, the better is the corrosion resistance. Microstructural studies on these composite coatings have revealed the retention of silicon nitride particles in the coating after corrosion tests, which was indicative of very little or no galvanic corrosion. A reduced tendency to pitting of the composite coatings as compared to nickel coatings was also observed. X-ray analysis of composite coatings exposed to 0.5M H2SO4revealed the presence of silicon dioxide in them, leading to enhanced passivation of the composite coatings with respect to pure nickel.

ISSN:0267-0844    

DOI:10.1179/sur.1991.7.3.216

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractA method is presented to separate, for the purpose of residual stress analysis, superimposed X-ray diffraction patterns arising from thin surface layers and substrates with similar crystal structures or from multilayer coatings in which the individual layers are of similar structure. The method is also suitable for use on bulk materials in which the stress gradient is very steep. Residual stress determinations were carried out in single and multilayer electrodeposited chromium coatings on steel. In the single coating the maximum residual stress was found to exist in the centre of the coating, whereas in the three layered coating the maximum values were found close to the substrate.

ISSN:0267-0844    

DOI:10.1179/sur.1991.7.3.221

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor

摘要:

AbstractChemical vapour deposition of chromium using CrCl2produced by the reaction of FeCl3with metallic chromium has been examined both thermodynamically and kinetically. The chemical processes occurring during coating have been examined by thermodynamic calculations and verified by comparison with experimental results. Kinetic measurements have been made on chromium diffusion in titanium alloyed mild steel. The diffusion promoting effect of titanium is explained thermodynamically. Reaction of FeCl3and chromium occurs in two stages. Initially FeCl2and CrCl2are formed above 200°C and the FeCl2formed reacts above 500°C, forming metallic iron and CrCl2. The beginning of the coating process, which is mainly diffusion controlled, is determined by the evaporation of CrCl2. The interdiffusion coefficient of chromium in the steel has been determined by various methods. Enhanced diffusion wasfound below 860°C, but the diffusion rate is too low to allow these temperatures to be used in practice. A strong dependence of the interdiffusion coefficient on chromium concentration was found in the temperature range 860–980°C.

ISSN:0267-0844    

DOI:10.1179/sur.1991.7.3.225

出版商:Taylor&Francis    

年代:1991

数据来源: Taylor