Microstructure and Mechanical Properties a New Iron-Base Material Used for the Fabrication of Sintered Diamond Tools

The main objective of the present work is to characterise the microstructure and mechanical properties of a new iron-base material which has been recently gaining ground in the manufacture of diamond impregnated tools as an economical substitute for cobalt and cobalt alloys. Its density, hardness and yield test properties have been directly compared to those of hot pressed Cobalt Extra Fine (CoEF) powder. It has been shown that the raw iron-663 bronze powder mix can be consolidated to a virtually pore-free condition by hot pressing at 880°C. Although the as-consolidated material is inferior to cobalt, it displays a favourable combination of hardness, yield strength and ductility, and seems to have a great potential for moderate and general purpose applications.

Microstructure Formation and Fracturing Characteristics of Grey Cast Iron Repaired Using Laser

The repairing technology based on laser rapid fusion is becoming an important tool for fixing grey cast iron equipment efficiently. A laser repairing protocol was developed using Fe-based alloy powders as material. The microstructure and fracturing feature of the repaired zone (RZ) were analyzed. The results showed that regionally organized RZ with good density and reliable metallurgical bond can be achieved by laser repairing. At the bottom of RZ, dendrites existed in similar direction and extended to the secondary RZ, making the grains grow extensively with inheritance with isometric grains closer to the surface substrate. The strength of the grey cast iron base material was maintained by laser repairing. The base material and RZ were combined with robust strength and fracture resistance. The prevention and deflection of cracking process were analyzed using a cracking process model and showed that the overall crack toughness of the materials increased.

Manufacturing of a NbC Particulate Reinforced P/M Iron-Base Valve-Guide Cup

The introduction of ceramic particulate into metallic powder will unavoidably lower the compressibility and formability of the mixed powder. In order to overcome these problems, in this study, warm compaction was introduced in the forming of an NbC particulate reinforced iron-base valve-guide cup, which is used in a combustion engine. Warm compaction was used not only because it can provide compacts with high green density but also it can increase the formability of the mixed powder. The part composed of an iron-base material which possesses 10wt%NbC with a relative density of 97.7%, a tensile strength of 815MPa, an elongation of 1.5%, a hardness of HRC33 and an impact toughness of 11J/cm2. Its working surface composed of an iron-base material which possesses 15wt% NbC with a high relative density of 98.2%, a tensile strength of 515MPa, a hardness of HRC 58 and a remarkable tribological behavior. The sintered part successfully passed a 500 hours bench test. No serious wear on the working surface can be observed after the test. Results indicated that the sintered part has excellent wear resistivity and the NbC particulate reinforced iron-base composite is a suitable material for parts that work under severe wear condition.