Agricultural Knives: Thermal Spray Case Study II
Recently, Kondex was faced with a field testing requirement that the OEM was unable to execute for cost reasons, though it was critical to our ability to supply thermal sprayed cutting components for its combine harvester. A great deal of scrutiny is placed on cutting components utilizing thermal spray hardfacing; if the hardfacing process is not carried out properly, the cutting edge will lose its ability to “self sharpen” and become dull well before its intended life cycle.
While there are a variety of standardized tests that can be utilized to verify material properties according to an Original Equipment Manufacturer’s (OEM) requirements, most agricultural equipment engineers rely heavily on field testing as the definitive test. To become approved, a supplier must pass a field test procedure lasting one or more harvesting seasons – an expensive and time-consuming process for the OEM.
This case study shows how we worked with the OEM to execute the field test and ultimately provide the best component for the OEM’s harvester.
The Field Test Comparison.
Though they were unable to conduct the test themselves, the OEM had its engineers help Kondex design a field test procedure that we would carry out, oversee, and report on. We developed the test procedure and located a customer with enough acreage to qualify for the testing. We worked with our OEM’s authorized dealer to install new Kondex blades alongside the same number of new blades from the current supplier, and instructed the machine operator to run as normal through the harvest season. When the harvest season was complete, all test blades were removed and analyzed in the Metallurgical Lab at Kondex.
The blades were cleaned, then weighed. The results show that Kondex blades lost less mass during the field testing. The average loss in grams for Kondex blades was 2.00 g and the average loss in grams for the Brand X blades was 2.50 g, (See Figure 1) – a 20% improvement in performance of Kondex blades.
A metallurgical evaluation was then carried out to understand the reasons for the discrepancy. The thermal spray hard coating on each sample appeared to be very similar, and both samples had good adhesion and minimal porosity. The relative hardness of the hardfacing material was measured and that also appeared consistent with both samples. (See Figures 2 and 3)
Figure 2. Micro-graph of Kondex Thermal Spray Hard Coating
Figure 3. Micro-graph of Brand X Thermal Spray Hard Coating
The Kondex Difference.
Upon further metallurgical examination, it was noted that the surface hardness of the Brand “X” blade material was softer by comparison. The softer layer in the Brand “X” parts was the result of a condition referred to as decarburization. Decarburization occurs when carbon steels are elevated to a high temperature in an atmosphere that contains oxygen. The amount of carbon in the surface of the material is diminished which in turn reduces the outer layers ability to harden through the heat treating process. The softer outer layer wears more quickly than a surface that is heat treated to the proper hardness. The decarburization process can be avoided through proper process selection as was shown with the Kondex parts. The results of this test show that the finest of details cannot be overlooked when producing high wear parts with high tech coatings.
What Does It Prove?
This case study is a great demonstration of the Kondex approach – we work hard to foster a “whatever it takes” attitude about satisfying customers’ needs – and of the long-term value to customers of using superior products designed for optimum performance.