摘要:

AbstractIn the present paper, an evaluation is made of the effect of the characteristics of raw materials on the characteristics of plasma sprayed WC–Co coatings and their abrasion wear performance. The raw materials and the coatings were characterised using X-ray diffraction techniques and metallography. The coatings were subjected to a standard ASTM abrasion wear test and their relative performances were explained based on their characteristics. Mainly, it was found that the coating characteristics were affected by the particle size, chemistry, phase composition, and porosity of the powder, factors which are dependent on the method of manufacture of the powder. In turn, it was found that the coating characteristics such as phase composition, porosity, and carbide size affected the abrasion wear performance. In general, it appears that better abrasion wear resistance is provided by denser coatings, which have a very fine distribution of hard phases (such asη-carbides) and an absence of softer phases.MST/790

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.4.382

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractContinuously cast copper and nickel samples were cooled using combined air and water jet. Temperatures close to the ingot surface were measured continuously during the cooling process and the coefficient of heat transfer from the ingot to the cooling water as a function of surface temperature was calculated with the aid of a suitable mathematical model. The experiments were carried out at spray water densities from 3·4×10−4to 2·72×10−3m3m−2s−lwith air pressures in the range 0·2–0·4 MPa. At lower flowrate or lower air pressure, no uniformity in droplet distribution within the spray cones could be achieved. It was found that the heat transfer coefficient when spraying an air and water mixture (air mist) is higher than that obtained for water spraying, densities being equal. As the water density is increased, the difference between the results obtained using the two methods is reduced. A formula was found by which the heat transfer coefficient can be calculated as a function of the surface temperature (above 250°C), the thermophysical properties of the material, and the water flux density (above 3·4×10−4m3m−2s−1).MST/844

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.4.389

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractAn extensive study of damage developed in a stretched spheroidised carbon steel sheet has been made. Bulge and punch stretching tests were employed. Damage of the stretched specimens was measured using a SEM. Nucleation strains for the different particles present in the sheet were determined. When damage is heterogeneously distributed within the sheet, a set of magnifications (so as to scan a large area) is strongly recommended. Area density (and volumetric fraction) of voids close to the sheet surface is at least 10 times greater than in the sheet thickness and increases exponentially with void size. A small proportion of MnS stringers (Vf=0·0005) plays a relevant role in the overall sheet damage. Necking and subsequent fracture in this type of sheet can be explained by a progressive tearing mechanism originating in the free surface and progressing deeper into the thickness of the sheet.MST/481

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.4.394

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractOn the basis of a theoretical analysis of published experimental data on the lengthening rate of sheaves of bainite in alloy steels, it is concluded that they lengthen at rates much faster than expected from paraequilibrium carbon diffusion controlled growth. The results are interpreted in terms of the mechanism of the bainite reaction and in the context of any solute atom–transformation interface interactions.MST/980

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.4.398

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractThe effect of the addition of 1 mol.-%MgO, BeO, or Y2O3on the dielectric behaviour of hot pressed AlN ceramic was studied in the temperature range 300–1000 K. It was observed that the dielectric constant and dielectric loss increase appreciably at all temperatures when these oxides are added to AlN. The effect of moisture on the dielectric behaviour was also studied for all the samples. It was observed that addition of the oxides increases the moisture absorption in pure AlN ceramic.MST/924

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.4.403

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

ISSN:0267-0836    

DOI:10.1179/mst.1989.5.4.407

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor