Production and Properties of Composite Titanium–Chromium Diboride Powders for Coating Deposition

Abstract

Conglomerated (Ti, Cr)B₂–NiAlCrWCoMoTi composite powders for thermal spraying and deposition through sintering followed by milling were produced. The main processes stages in the production of powders, such as mixing, grinding, sintering, milling, and classification, were optimized. The effect of briquette sintering temperature on the milling efficiency and finished powder yield was determined. Solid-phase sintering was found to be feasible at temperatures 200–300ºC lower than the liquid-phase formation temperature. The influence exerted by the ratio of the refractory to metal components on the technological properties of the powders was studied. The flowability of the powders increased nonlinearly with a higher content of the metal component and greater particle sizes. The influence exerted by the ratio of the refractory to metal components on the morphology of powder particles was analyzed. The powder particles had a fragmentary elongated shape with a higher content of the refractory (Ti, Cr)B₂ component, while they acquired a more oval shape with a greater amount of the metal component. The composition and microstructure of individual powder particles were examined. They showed a heterophase microstructure. The uniform distribution of structural components in individual powder particles was found to depend on the mixing and grinding modes for powder mixtures. The uniform distribution of structural components in individual particles requires that particles of the starting powder components be significantly smaller (one-fifth or even less) than particles of the finished composite powder. The difference in the starting particle sizes for refractory and metal components should be no more than 2–3 times.