Novel Application Method for Improved Fatigue Life of Laser Applied Hardfacing
Publication Date: 2004-Aug-24
The IP.com Prior Art Database
Detailed Description of the Invention Novel Application Method for Improved Fatigue Life of Laser Applied Hardfacing Hardfacing is applied to the OD of MWD/LWD tools to reduce wear due to formation contact while drilling and increase the service life of the tool. While the use of hardfacing does provide wear protection, it is possible that the hardfacing can reduce service life by premature fatigue cracking. Cyclic bending loads induced during directional drilling can form cracks in the brittle layer of hardfacing. Cracks that formed in the hardfacing can propagate into the base material, and the tool must either be reworked or scrapped. One of the more recent advances in hardfacing technology is the use of lasers to apply coatings. Laser cladding offers many advantages, including improved fatigue life. Figures 1 and 2 illustrate how a laser-based coating is typically applied. The weld path is a continuous series of overlapped weld passes that are perpendicular to the MWD tool axis. Actual width and geometry, as well as coating thickness, can be varied depending on design intent. In addition, another common weld path used is a "circumferential"-type path (shown in Figure 3). This is applied using a continuous overlapping helical path that covers the entire circumference of a section of the tool OD. Note that in all laser paths currently used, the weld beads are overlapped to form a continuous hardfacing surface. Figure 1: Typical application of laser applied hardfacing on the OD of a MWD tool. The weld beads are overlapped in a direction that is perpendicular to the tool axis. Figure 2: Typical laser path used to apply hardfacing (shown relative to tool axis). Figure 3: Circumferential-type hardfacing. The hardfacing is applied in a continuous helix around the entire circumference of the tool. of tool size, base material, hardfacing powder formulation, and laser cladding parameters.