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In the first part of this article in our last issue P. L. HURRICKS considered the wear resistance of sprayed coatings when subjected to adhesive and abrasive action. In this part he is concerned with the friction of sprayed coatings on bearing and journal surfaces.

The first part of this paper appeared in our November/December issue and dealt with fretting wear behaviour of mild steel from room temperature to 600°C in air. The general mechanism for fretting is discussed at all temperatures where normal oxidative processes become involved. The nature of fretting wear is also covered and the effects of temperature are described. In this part of the paper, the discussion is continued to include triboxidation, delamination theory, atmospheric environment, transition temperatures, activitation energy and other factors affecting the influence of temperature on fretting.

WEAR is one of the major ways by which a material part ceases to be useful, others are corrosion, obsolescence and breakage. It is the consequence of relative motion and in industrial plant and equipment it has always been accepted as inevitable that it should lead to heavy expenditure for maintenance and replacement. Historically, wear is a well established fact, yet our knowledge of the technology is extremely limited. It has become a way of life that we compensate for wear when it no longer can be tolerated, yet need this be so? This article examines the problem, and primarily from the unlubricated point of view, describes the various types of wear and the way material selection or modification can be used to limit wear.

The paper deals in some detail with the fretting wear behaviour of mild steel from room temperature to 600°C in an air atmosphere. The general mechanism of fretting for mild steel is discussed both at the lower temperatures and also at higher temperatures where normal oxidative processes become involved in the fretting mechanism. Both surface metallographic observations and surface SEM observations are presented in support of the wear processes involved. It is shown that there is a well defined wear transition temperature occurring in the region of 200°C together with the possibility of a second transition temperature occurring between 500 and 600°C. Finally, some consideration is given to the activation energy for tribo‐oxidation under fretting conditions and the manner in which the rate controlling factor changes from adhesion to oxidation as the temperature of wear increases.

The reduction of wear by the use of sprayed surface coatings holds considerable potential at a time when Industry is becoming more conscious of the need to reduce its operating costs. Control of wear is unlikely to become a true science due to the arbitrary nature of the conditions that produce the effect and although no truly economic solution exists for completely preventing surface degradation, it can be minimized to acceptable limits. It is the purpose of this article to present an approach to the use of sprayed surface coatings in tribological situations. Common wear types are briefly described and the philosophy behind the protective surface layer in relation to surface geometry is outlined. The performance of sprayed coatings in adhesive and abrasive wear situations is evaluated and discussed. In addition, the use of sprayed deposits for lubricated bearing surfaces is considered as well as the application of low friction coatings by the spray method.

AT THE Society of Automotive Engineers' Mid‐Year meeting at Detroit in May there were several papers presented which gave details of work that has been sparked off due to the reporting of thickening of crankcase oils in motor cars used at high speeds for long periods of time. This results from increasing use of motorways where it is now possible to travel hundreds of miles at speeds that rarely drop below 60 to 70 mph. Cases have been reported where the engine oil have thickened up to a grease consistency.

The purpose of this paper is to study the sliding and the vibrating fretting tests mechanism of h‐BN micro‐particles when used as a lubricating grease‐2 additive.

The fretting tests were conducted on steel/steel contacts using both vibrating fretting apparatus and the shaft‐sleeve slide fitted tester. The wear scars were characterized with profilometry. The tribological properties of grease‐2 compounded with h‐BN additive were also compared to those obtained for the commercial product Militec‐4.

The experiment showed significant differences between the results obtained from the vibrating fretting and the shaft‐sleeve sliding fitted tests. Adding h‐BN to the lubricant leads to a better performance in the shaft‐sleeve slide regime than in the steel/steel vibrating test condition.

The results of the experimental studies demonstrate the potential of h‐BN as an additive for preventing fretting sliding, and can very useful for further application of compound grease‐2 with h‐BN additive in industrial equipment.

The aim of the research is to investigate the influence of gas metal arc welding on the wear performance of worn concussor jaws.

Worn parts were welded using the gas metal arc welding process. Various wires were used for this purpose. These welded parts were subjected to wear tests under different loads, and changes in the hardness and microstructures were examined. A pin‐on‐disc wear test apparatus was used.

As a result of this study, the following findings are reported: wear rates were significantly increased with the increasing of load and wear distance; the hardness of the weld metal of the welded specimens changed depending upon the chemical composition of the weld wire; with the increasing carbon, manganese and chromium in the weld wire, wear resistance increased; in the present study, specimens B and C showed better wear resistance; therefore these specimens are suitable for using in concussor jaws.

Electrodes were limited with four wires, for welding gas arc welding methods were applied, loads were limited with 10, 25, 40 N, welded parts were subjected to wear test, hardness test, microstructures were examined.

For future work, instead of buying worn concussor jaws, they are repaired with the gas metal arc welding process using various weld wires. By this process, working life of the jaws can be extended and vast economical benefit may also be obtained.

This paper fulfils an identified information need and offers practical help to the industrial firms working with alunit ore and rock crasher and also to the academicians working on wear of materials.

This paper aims to research the tribological features of AISI 1035 steel, boronized at various parameters.

The samples were boronized via box boronizing method. By using Ekabor 2 powders, boronizing was conducted at 840, 880, 920, 960 and 1,000°C for two, four and six hours. Wear resistance of boronized samples at determined parameters were analysed. Wear experiments were conducted under 40 N constant load at pin‐on‐disk experiment setup. Also, microstructures and microhardness values of boronized samples were analysed to determine the most suitable boronizing parameters against wearing.

As a result of this study, the following findings are reported: it was determined as the temperature increased, the thicker the boride layer obtained during the boronizing. In the case of longer boronizing time, the distinct columnar structure was clearer. Whenever applying higher temperature and longer boronizing time, wear decreased and hardness values increased. It was also determined that when boronizing was conducted at 900 and 1,000°C for at least four to six hours, better results were obtained. Furthermore, the increment in the boronizing temperature and longer duration caused an increase in hardness from the surface to inwards and thus a decrease in wear ratio.

In the present study, only 40 N is used for a wear load and that is the limitation of the research.

Boronizing of the parts using 900 and 1,000°C temperature and four to six hours time, the better results can be obtained. Wear resistance can be improved in the determined temperature interval for boronizing process. Therefore, the industrial firms can be gained huge economical profits.

The outcome of the study will be beneficial for the academicians and industrial firms working on wear process. The service life of the steel parts can be extended via boronizing of steels working on quarries.