INFLUENCE OF HOT ISOSTATIC PRESSING PARAMETERS ON STRUCTURE AND PROPERTIES OF COBALT-BASED ALLOYS OBTAINED BY SELECTIVE LASER MELTING

The paper examines the microstructure and mechanical properties of experimental compositions of a heat-resistant cobalt superalloy, produced by the method of selective laser melting (SLM). Strengthening in the studied materials is achieved by the formation of a fine-celled structure of a solid solution based on cobalt and highly dispersed intermetallic and carbide phases. By the EMPA (electron micro probe analysis) method, the ratio of chemical elements in these phases was evaluated and their type was determined. It was estimated that the tantalum content determines the strength properties of the alloy. It was found that dispersed particles formed during the synthesis have a positive effect on the creep resistance at 800 °C temperature, whereas at 1100 °C temperature the destruction occurs along the boundaries of the persisted structure of synthesis, regardless of the alloying and morphology of structural components.

Two linkage-region fragments isolated from skeletal keratan sulphate contain a sulphated N-acetylglucosamine residue

Peptido-keratan sulphate fragments were isolated from the nucleus pulposus of bovine intervertebral discs (6-year-old animals) after chondroitin ABC lyase digestion followed by digestion of A1D1 proteoglycans by diphenylcarbamoyl chloride-treated trypsin and gel-permeation chromatography on Sepharose CL-6B. Treatment of these peptido-keratan sulphate fragments with alkaline NaB3H4 yielded keratan sulphate chains with [3H]galactosaminitol end-labels, and these chains were further purified by gel-permeation chromatography on Sephadex G-50 and ion-exchange chromatography on a Pharmacia Mono-Q column in order to exclude any contamination with O-linked oligosaccharides. The chains were then treated with keratanase, and the digest was chromatographed on a Bio-Gel P-4 column followed by anion-exchange chromatography on a Nucleosil 5 SB column. Two oligosaccharides, each representing 18% of the recovered radiolabel, were examined by 500 MHz 1H-n.m.r. spectroscopy, and shown to have the following structures: [formula: see text] The structure of oligosaccharide (I) confirms the N-acetylneuraminylgalactose substitution at position 3 of N-acetylgalactosamine in the keratan sulphate-protein linkage region found by Hopwood & Robinson [(1974) Biochem. J. 141, 57-69] but additionally shows the presence of a 6-sulphated N-acetylglucosamine. Electron micro-probe analysis specifically confirmed the presence of sulphur in this sample. This sulphate ester group differentiates the keratan sulphate linkage region from similar structures derived from O-linked oligosaccharides [Lohmander, De Luca, Nilsson, Hascall, Caputo, Kimura & Heinegård (1980) J. Biol. Chem. 255, 6084-6091].