Influence of heat treatment on properties of SD251-PH1 composite produced by additive SLM technology

Abstract

This study evaluates how heat treatment affects the structure and properties of the engineered composite material SD251-PH1. This material was formed by mixing two powder blends in a weight ratio of 90 wt. % WC-Co powder SD251 with 10 wt. % of a PH1 precipitation hardening powder of the stainless steel. Samples were prepared from this mixture on an SLM additive device. The printed samples were then divided into groups. Some of them were left in the initial state and the rest were used for heat treatment based on the standard AMS 5659. Light and electron microscopy metallographic analysis together with X-ray diffraction analysis were then used to evaluate structural and phase changes in the prototype samples. The main attention was paid to changes in the phase composition of the samples. In addition, changes in the size and shape of the pores and tungsten carbide (WC) grains were studied. The metallographic analysis was supplemented by an evaluation of the changes in their mechanical properties and wear resistance. Vickers hardness measurements and the ball on disc test were used for this purpose. The experiments showed that the selected heat treatment processes precipitated new structural phases which differed from the original sample structure in terms of shape, size, chemical composition, and mechanical properties.