Left Imagine: Non-uniform Quenching (Mottled)
Visual Characteristics: The surface shows obvious interweaving of "blue" (quenched areas) and "red/brown" (unquenched or tempered areas).
Process Defect: This usually means uneven heating or inconsistent cooling speed during the quenching process. The red parts may have thicker oxide scale or simply did not reach the quenching temperature, leading to incomplete microstructural transformation.
Functional Differences & Performance Impact:
-Inconsistent Hardness: The blue parts are hard (usually HRC 50-60), wear-resistant; the red parts are soft (possibly only HRC 20-30), and wear easily.
-Premature Wear: In actual operation, the soft red areas will wear much faster than the hard blue areas. This causes the drive wheel surface to become uneven, even developing "step" wear.
-Drive Slippage: An uneven surface leads to poor meshing with the track or drive chain, increasing transmission noise and even causing slippage under high load, reducing tractive force.
-Stress Concentration: The junction between hard and soft areas is prone to stress concentration, becoming a starting point for cracks, increasing the risk of tooth breakage or chipping.
Right Imagine: Uniform Quenching (Large area blue)
Visual Characteristics: The surface color is uniform, showing a consistent dark blue or gray-blue, which is the typical oxide color after quenching + tempering, indicating the entire working surface has undergone full heat treatment.
Process Advantage: It indicates that the drive wheel was fully heated and cooled uniformly during quenching, and the entire tooth or surface microstructure has transformed into high-hardness martensite (or tempered martensite).
Functional Differences & Performance Impact:
-High Wear Resistance: The entire contact surface has consistent and high hardness, effectively resisting friction from track plates or chains, significantly extending service life.
-Strong Fatigue Resistance: Uniform hardness means a more reasonable distribution of internal residual stress, allowing it to better withstand repeated impact loads without easily generating fatigue cracks.
-Stable Meshing: Uniform surface hardness and consistent wear rate allow it to maintain good geometric shape for a long time, ensuring smooth meshing with transmission components and improving transmission efficiency.
-High Load Capacity: Under heavy loads, it will not suffer plastic deformation (i.e., "crushing") due to local soft spots.
Summary Table:
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