Investigation of the main influencing parameters on the degassing behavior of titanium carbonitrides using mass spectrometry

Abstract

It is well known that titanium carbonitrides (Ti(C,N)) release carbon monoxide (CO) and nitrogen (N2) upon heat treatment, which can influence further processing such as sintering. Thus a deeper understanding concerning the driving forces of the degassing behavior could facilitate the development of further processing steps. Therefore, the focus of this study was put on determining the main influencing factors of the degassing behavior of titanium carbonitrides during heat treatment. For this purpose, an application-oriented characterization method by modifying an evolving gas analysis device (EGA) was developed. Quadrupol mass spectrometry (MS) was applied to monitor the gas evolution as a function of temperature under vacuum. The evolving CO and N2 were transported to the mass spectrometer using a helium carrier gas flow. Thermogravimetric analysis was deployed to complement the mass spectrometry data and to further elaborate on the outgassing behavior of the different sample species.Titanium carbonitride powders with different C/N/O ratios, grain size as well as free carbon content blended with typical binder metals (Co, Ni and Co+Ni) were investigated regarding their degassing behavior. The different C/N/O ratios influenced decisively the CO as well as the N2 outgassing in terms of quantity and temperature range. Consequently, a unique outgassing pattern, a “finger print”, was identified for each titanium carbonitride powder type. An altered grain size on the other hand, did not lead to a changed gas evolution. However, the content of free carbon was influencing the CO and the N2 outgassing significantly. The binder type, by contrast, was influencing the N2 evolution to a higher degree than the CO evolution.