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An appreciation of the material from which modern printed circuit board drills are fabricated and an understanding of the salient geometric design features incorporated in such tooling will help those involved with the drilling process in determining optimum operating procedures and in identifying the underlying causes of hole deficiencies.

THIS paper shows briefly the origins and development of a comparatively new and certainly important branch of engineering science. For many years the alloys of the light metals, particularly of aluminium and magnesium, have been developed, until the term “light alloys” has come to be generally accepted as indicating the alloys of the light metals or any metallic alloy having a density of less than about 3·8. Towards the other end of the density scale are now being developed alloys of the heavy metals, mainly tungsten and tantalum. The techniques of production and manufacture of these two groups are very different: whereas the light alloys are produced and manipulated mainly by melting, casting, annealing, and forging, the heavy alloys are produced by various processes of powder metallurgy, resulting in substances with densities of 15 or more.

The name Dymet Alloys Ltd is familiar to everyone in the printed circuit industry; indeed it would be no exaggeration to say that they are the foremost UK producer of multilayer quality PCB drills.

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.

Machining operations on multilayer circuit boards play the two major roles of establishing the finished geometry of the board and leading to the interconnection of the various conductor layers and it is likely that for some considerable time carbide cutting tools will continue to be used in the machining process. Fundamental and detailed considerations of the parameters influencing machining are presented prior to analysing the two predominant areas of use. Mention is made of some advanced machining techniques, involving mechanical, chemical and laser methods.

This paper aims to improve the tribocorrosion properties of 316L, thus WC/Ni60 coated 316L was prepared by thermal spraying technique.

Composition and microstructure of WC/Ni60 coating was investigated, and tribological properties of 316 L and WC/Ni60 coating were studied under dry sliding, deionized water and artificial seawater.

The results showed that WC/Ni60 coating was lamellar structure, and the phase composition consisted of γ-Ni solid solution, carbides and borides. Furthermore, the hardness and corrosion resistance of 316 L in static seawater and wear resistance in dry sliding were improved by WC reinforced nickel-based coating. Furthermore, tribocorrosion results demonstrated that wear resistance of WC/Ni60 coating was also significantly better than 316 L, especially for higher load at artificial seawater. The reason can be attributed to the fact that the passive film of WC/Ni60 coating consisted of tungsten carbide, Ni(OH)2 and FeOOH for WC/Ni60 coating and only FeOOH for 316 L.

According to this study, it can be concluded that WC phases acted as a role in resisting the wear damages. Meanwhile, Ni-based materials performed well in corrosion resistance. Thus, the combined-effect Ni-based alloys and WC phases in WC/Ni60 coating showed better tribocorrosion performance than 316 L.

Taguchi's technique is best suited to optimize a single performance characteristic yielding an optimal setting of process parameters. A single setting of process parameters may be optimal for one quality characteristics but the same setting may yield detrimental results for other quality features. Thus the purpose of this paper is to describe simultaneous optimization of multi‐characteristics.

The multi‐machining characteristics have been optimized simultaneously using Taguchi's parameter design approach and the utility concept. The paper used a single performance index, utility value, as a combined response indicator of several responses.

A simplified model based on Taguchi's approach and utility concept is used to determine the optimal settings of the process parameters for a multi‐characteristic product. The model is used to predict optimal settings of turning process parameters to yield the optimum quality characteristics of En24 steel turned parts using TiC coated carbide inserts. The optimal values obtained using the multi‐characteristic optimization model have been validated by confirmation experiments. The model can be extended to any number of quality characteristics provided proper utility scales for the characteristics are available from the realistic data.

The proposed methodology can be applied to those industrial situations where a number of responses are to be optimized simultaneously.

The paper discusses a case study on En24 steel turned parts using titanium carbide coated tungsten carbide inserts. The material, En24 steel, has wide applications in aerospace, machine tools, automobiles, etc. The proposed algorithm is easy to apply.

This paper aims to compare the wear performance of carbon steel specimens clad with TiC, WC and TiN powders by the gas tungsten arc welding (GTAW) method under optimum processing conditions.

Various ceramic powders (TiC, WC and TiN) with equal percentages by weight were prepared for use as cladding materials to compare their effects on wear resistance. The wear behaviors of different cladding specimens were evaluated with a rotating-type tribometer under dry sliding conditions. The cladding microstructures were characterized by optical microscopy, scanning electron microscopy and X-ray energy dispersive spectrometry.

The experimental results confirmed that the hardness was also much higher in the carbon steel with cladding than in carbon steel without cladding. The pin-on-disc wear test showed that the wear-resistance of ceramics clad with TiC is better than that in ceramics clad with WC or TiN. The wear scar area of the specimen with TiC cladding was only one-tenth that of carbon steel without cladding.

The experiments confirm that the cladding surfaces of ceramic particles reduce wear rate and friction.

Metalworking fluids can significantly increase the tool life in titanium cutting, however, full-scale cutting tests to determine the performance of metalworking fluid are expensive. The aim of this study is therefore to introduce a reliable and inexpensive alternative testing method.

A newly developed in-process tribometer allows emulating the sliding conditions of the chip formed in cutting as closely as possible. It uses a cutting action in front of a pin to eliminate the influence of the oxidation layer. To observe the wear pattern on the pin, adhering workpiece material is removed by selective etching. A high temperature oxidation test is used to study the wear mechanism.

The wear pattern on the pin correlates well with the wear pattern observed on cutting tools when using the same metalworking fluid while being much more cost-effective than a tool life test. The high temperature oxidation test reveals that cobalt leaching is causing notch wear.

The correlation between pin and tool wear is verified for the case of roughing turning of titanium with cemented carbide tools and two metalworking fluids.

The method is applicable in an industrial context, potentially replacing the currently used tribological analyzes.

Submitted in connection with the special issue “young tribologists – insights into the work of the new generation”.

Methods tailored to model the tool wear in titanium cutting are rare. For the first time, an in-process tribometer, which is especially suited for the analysis of titanium cutting, is used to assess the wear behavior. The design of the high temperature oxidation test is new.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0311

GERMANY Metals in contact with aqueous solutions. When metals are brought into contact with aqueous solutions at room temperature there is said to be an initial or ‘incubation’ period which may be of extremely short duration, almost a transient. After this period corrosion may increase rapidly to a thousand times its initial value or more, or may decrease even more rapidly. The latter process can be followed only with a cathode ray oscilloscope. The formation of local elements is assumed to be the cause of the processes observed. The effect on corrosion is shown at the instance of aluminium of different degrees of purity. Dissolution speeds are 6 g./sq.m./day for Al 99.998% rising to 190,000 g./sq.m./day for Al 99.2%.— (F. Tödt, Werkstoffe & Korrosion, 1954, 5, (11), 430–433).