Influence of Boron Additions and Heat Treatments on the Fatigue Resistance of CoCrMo Alloys

Abstract

Cobalt-based alloys are widely used in the manufacture of joint prostheses. In this study, the effect of boron additions and heat treatment on the ASTM F75 was evaluated by rotating bending fatigue. The boron ranged from 0.06–1 wt %. The alloys were tested in as-cast and heat-treated conditions. In the as-cast condition, the infinite life was observed at 380 MPa, improving to 433–615 MPa according to the amount of boron added. In the heat treatment condition, the fatigue resistance was improved only in the base alloy. The addition of 0.06 wt % boron and heat treatment led to the same resistance as in the as-cast condition. Adding large amounts of boron combined with heat treatment diminished the fatigue limit. The fracture analysis revealed primarily brittle behaviour with some ductile features even on the same sample; only the heat-treated alloy with 0.06 wt % boron was clearly ductile. This alloy also exhibited notably better toughness to crack propagation.

A review on manufacturing processes of cobalt‐chromium alloy implants and its impact on corrosion resistance and biocompatibility

“…95 The forged CoCr alloys are currently the most commonly used alloy systems for devices that are implanted at loadbearing sites such as artificial joints. 96 A typical microstructure of forged CoCr alloy is shown in Figure 5A,B. 97 95…”

“…Hence, forged alloys have excellent fatigue, yield, and tensile strength as a result of the unique microstructure, where the presence of two different crystal structures hinders the motion of dislocations to significantly increase strength as compared to cast alloys 95 . The forged CoCr alloys are currently the most commonly used alloy systems for devices that are implanted at load‐bearing sites such as artificial joints 96 . A typical microstructure of forged CoCr alloy is shown in Figure 5A,B 97 .…”

Effects of Al2O3 Addition on the Microstructure and Properties of CoCr Alloys

“…In addition, in the processing of CoCr alloys, their microstructure and properties under different processes have been extensively studied [2,[13][14][15][16][17][18], including a large number of studies on heat treatment processes and surface modification of CoCr alloys [19][20][21][22][23]. Cast CoCr alloys with coarse microstructures and solidification defects have been reported [24].…”

Effect of TiB Orientation on Near-Threshold Fatigue Crack Propagation in TiB-Reinforced Ti-3Al-2.5V Matrix Composites Treated with Heat Extrusion

“…Prior work has demonstrated that the mechanical properties of stainless steels [15] and of alloys of magnesium [16], cobalt–chromium–molybdenum [17], and titanium [18,19,20,21,22,23,24,25,26,27,28,29,30] can all be improved via the addition of boron. The combination of titanium and boron generates whiskers of titanium boride (TiB) as a result of the reaction Ti + TiB 2 → 2 TiB.…”