Palmqvist fracture toughness of a new wear-resistant weld alloy

Abstract

The Palmqvist fracture toughness method was applied in a new fashion to measure the fracture toughness of a new wear-resistant alloy in both a powder product for plasma-transferred arc (PTA) welding and a wire product for metal inert gas (MIG) welding. Cracks were observed at high loads with a linear relationship between load and crack length indicating that only Palmqvist cracks occurred in the alloys. The fracture toughness for the no-preheat and preheat PT40 welds are 15.6 6 0.3 MPa m 1/2 and 17.6 6 0.1 MPa m 1/2 , respectively, and for the no-preheat and preheat MG40 welds are 12 6 1 MPa m 1/2 and 20.5 6 0.2 MPa m 1/2 , respectively. Observations of the cracks show evidence of ligaments indicating that the toughness mechanism is due to crack bridging. The microstructural scale and morphology correlates with the fracture toughness, and as the structural scale decreases, the fracture toughness increases.

Toughening mechanism for Ni–Cr–B–Si–C laser deposited coatings

“…The crack growth paths and fracture surfaces were studied using both OM and SEM. An attempt was made to measure the toughness of the deposits by indentation at loads of 125, 250, 500, 1000 and 1500 N using the Palmqvist indentation technique [19] which was unsuccessful mainly because of insufficient thickness of the deposits. As a result, the cracking rate was taken as a measure of toughness.…”

“…To overcome such a limitation, an attempt was made to measure the fracture toughness of laser deposited Colmonoy 69 coatings using Palmqvist indentation technique. This technique is based on indentation by a Vickers diamond pyramid indenter under known loads which are higher than some threshold necessary to generate cracks [19]. If the material is relatively hard and brittle, cracks will be generated at four corners of the indents.…”

“…If the material is relatively hard and brittle, cracks will be generated at four corners of the indents. The fracture toughness could then be measured using the following equation [19]:…”

“…Hence, a toughening mechanism for these alloys will be most favorable if it is not accompanied by a significant loss of hardness. Such an approach in which enhancement of fracture toughness occurs while preserving the high hardness of the deposits has been successfully tested for Febased wear resistant alloys [18,19]. In that case, the key to obtaining a favorable combination of high hardness and high fracture toughness was refinement of the borocarbide precipitates.…”

Effect of heat treatment on the microstructure, hardness and abrasive wear resistance of high chromium hardfacing

“…2). The polished surfaces were intended by Vickers indenter at loads 294 N or 981 N. Existence of crack was measured by optical microscopy (Meacham et al 2006;Duszová et al 2011). The Palmqvist toughness W G (N/mm) was determined as:…”